Abstract
Zingiber Mill. is the second-largest genus of the Zingiberaceae family. The members of this genus are known for their diverse applications in food, cosmetics, pharmaceuticals, and healthcare fields due to their richness in bioactive components found in essential oils (EOs). This study aims to provide information about EOs’ chemical composition and biological activities from 23 Zingiber species. A literature survey was performed via scientific databases, including PubMed, Scopus, Web of Science, Google Scholar, and ethnobotanical textbooks. Clustering analysis was conducted using the Unweighted Pair Group Method with Arithmetic Mean (UPGMA) to construct phylogenetic trees. Various studies have revealed that β-pinene, α-pinene, β-caryophyllene, β-elemene, bicyclogermacrene, sabinene, camphene, linalool, (E)-nerolidol, terpinen-4-ol, 1,8-cineole, humulane-1,6-dien-3-ol, β-phellandrene, and zerumbone are representative ingredients of 23 Zingiber EOs. Pharmacologically, the current results have recorded several Zingiber species related to antioxidant (Z. plicatum), antimicrobial (Z. rubens, Z. castaneum, Z. nitens, Z. tamii, Z. magang, Z. densissimum, Z. cornubracteatum, Z. nudicarpum, Z. ottensii, Z. recurvatum, Z. vuquangense, Z. eberhardtii, and Z. skornickovae), anti-larvicidal (Z. castaneum, Z. mekongense, Z. nitens, Z. ottensii, Z. neotruncatum, Z. cornubracteatum, Z. nudicarpum, Z. collinsii, and Z. recurvatum), antidiabetic (Z. atroporphyreus), anticancer (Z. ottensii), and cytotoxic (Z. rubens and Z. ottensii) properties. Cluster analysis showed that Z. densissimum and Z. plicatum had the highest phytochemical similarity, followed by Z. mekongense and Z. vuquangense, and Z. cornubracteatum and Z. nudicarpum. Additionally, the dendrogram offers crucial insights into the phytochemical relationships among Zingiber species, highlighting the chemical similarities between leaves, stems, rhizomes, roots, inflorescences, and fruits. This is the first report to highlight the recent bioactivity assessments and summarize the EO components of different parts from 23 Zingiber species and their promising applications in modern medicine.
Introduction
Globally, Zingiber Mill. is the second-largest genus belonging to the Zingiberaceae family with around 210 species, 1 and they are widely known for their various uses, such as spices/foods, ornamentals, and medicinal plants.2,3 These species are commonly distributed in subtropical and tropical regions worldwide. In particular, many Zingiber species have been recorded in Asian countries, such as Vietnam, China, India, Bangladesh, Malaysia, Thailand, Laos, Cambodia, Myanmar, Indonesia, etc (Figure 1).2,3 The ethnobotanical uses of the genus Zingiber (eg, Z. zerumbet, Z. officinale, Z. corallinum, Z. mioga, etc) comprise a diverse range of applications, such as spices, flavor, color, and aroma of food, as well as its members have also been used in traditional medicine to treat digestive disorders (nausea, vomiting) and stomach ulcers, dysentery, fever, pain, respiratory disorders, and so on.4,5 This genus has been studied for various modern pharmacological effects, including antioxidant, antimicrobial, larvicidal, anti-obesity, anti-inflammatory, anti-diabetic, neuroprotective, cardiovascular protective, cytotoxic, anti-cancer, and other medicinal effects.4,5 Phytochemical studies on Zingiber species have found a variety of bioactive secondary compounds, such as flavonoids, diarylheptanoids, volatile oils, organic acids, gingerols, steroids, and terpenoids; especially essential oils (EOs), a volatile phytochemical compound that has been widely used in traditional medicine and has many pharmacological effects that have recently attracted attention in medicine and cosmetic fields.4–6 Recently, numerous scientific studies demonstrated the Zingiber plants’ (eg, Z. zerumbet, Z. officinale, etc) antimicrobial, 7 antifungal, 8 antiviral, 9 antioxidant, anti-inflammatory, anti-allergic, and anticancer potential.4,5,9,10 According to the Flora of Vietnam, several members of the genus Zingiber are emerging medicinal resources, receiving much attention from domestic and international scientists, especially new species discovered in Vietnam in recent years (eg, Z. collinsii, Z. densissimum, Z. eberhardtii, Z. magang, Z. tamii, Z. nitens, Z. ottensii, Z. vuquangense, etc). Interestingly, some Zingiber species like Z. collinsii, Z. eberhardtii, Z. mekongense, Z. gramineum, etc are widely known and used locally as medicines, spices, foods, cosmetics, and ornaments.11–14 EOs have long been used as flavorings in the food and perfume/cosmetic industries 15 ; thus, EOs extracted from Zingiber species are an important natural resource. Although numerous phytocompounds and bioactivities of the genus Zingiber have been investigated, mainly as EOs in recent years, a comprehensive summary of the EO constituents of this genus, especially those newly Zingiber species reported (Figure 1), is still scarce. Therefore, this is the first work to highlight the recent bioactivity assessments and summarize the EO compositions of different parts from 23 Zingiber species, including Z. acuminatum, Z. atroporphyreum, Z. castaneum, Z. cornubracteatum, Z. collinsii, Z. densissimum, Z. eberhardtii, Z. gramineum, Z. mekongense, Z. monophyllum, Z. magang, Z. tamii, Z. neotruncatum, Z. nitens, Z. nudicarpum, Z. ottensii, Z. pellitum, Z. plicatum, Z. recurvatum, Z. rufopilosum, Z. rubens, Z. skornickovae, Z. vuquangense (Figure 1) and their promising applications in modern medicine.
The first records and distribution of 23 Zingiber species.
The main aims of this work are (1) to provide information on the EOs of different parts from 23 Zingiber species; (2) to compare the EO compositions from the various parts and their distribution areas; (3) to discuss the potential of Zingiber species as a source of phytotherapy or herbalism that can be applied to treat or prevent various ailments and the importance of application of these Zingiber species in the pharmaceutical and healthcare fields soon; and (4) to discuss on toxicity and safety issues of EOs as well as recommendations for conservation, cultivation and development of these Zingiber species to become a valuable source of medicinal herbs will be a highlight in the future.
Research Methodology
Literature Search and Selection Criteria
A literature survey concerning the selected Zingiber species was conducted using scientific databases, including PubMed, Scopus, Web of Science, Google Scholar, and ethnobotanical textbooks, between 1810 and 2024. Conference papers, local books, and master's and doctoral dissertations were also used to collect information. The Plants of the World Online (https://powo.science.kew.org/), the World Flora Online (https://www.worldfloraonline.org/), and the Flora of China (http://www.efloras.org/) were used to identify scientific names, synonyms, and morphological characteristics of selected Zingiber species. English and Vietnamese articles were included if the study design was eligible and concerning outcomes.
The search terms focused on the EO profiles and their pharmacological effects from 23 Zingiber species, using keywords like “Zingiber acuminatum”, “Zingiber atroporphyreum”, “Zingiber castaneum”, “Zingiber cornubracteatum”, “Zingiber collinsii”, “Zingiber densissimum”, “Zingiber eberhardtii”, “Zingiber gramineum”, “Zingiber magang”, “Zingiber mekongense”, “Zingiber monophyllum”, “Zingiber neotruncatum”, “Zingiber nitens”, “Zingiber nudicarpum”, “Zingiber ottensii”, “Zingiber pellitum”, “Zingiber plicatum”, “Zingiber recurvatum”, “Zingiber rufopilosum”, “Zingiber rubens”, “Zingiber skornickovae”, “Zingiber tamii”, “Zingiber vuquangense” combined with “chemical compositions” or “pharmacological effects” and “essential oils” so that only publications related to the topic of this study were included. Articles with inappropriate study designs or unclear results will be excluded from this review. Therefore, the survey results obtained approximately 108 publications relevant to the title of the current study. Several articles in the introduction and discussion sections were also included to provide additional information without being associated with the search parameters.
The chemical structures of the EO components were 1checked using PubChem (https://pubchem.ncbi.nlm.nih.gov/) and ChEBI (https://www.ebi.ac.uk/chebi/init.do) databases.
The UPGMA Cluster Analysis and Jaccard's Similarity Index
The data collection for this study involved an extensive review of previous research focusing on the major phytochemical composition of EOs from 23 selected Zingiber species (Table 1). Each species was assessed for the presence or absence of various phytochemicals, with the results recorded in a binary format. A value of ‘0’ was assigned where a particular phytochemical was not found in a species, while ‘1’ indicated its presence. This binary dataset served as the foundation for further numerical analysis.
Major Constitutions Identified from Zingiber EOs.
Clustering analysis was conducted using the Unweighted Pair Group Method with Arithmetic Mean (UPGMA), a widely used method for constructing phylogenetic trees. This approach was chosen to investigate the similarity of phytochemical compounds found in each species to determine whether the species share similar compounds or exhibit distinct chemical profiles. Understanding these similarities and differences is crucial for interpreting chemotaxonomic relationships and exploring potential ecological or evolutionary patterns.
The Jaccard similarity index was employed as the similarity measure, as it accurately captures the degree of overlap between the species based on their phytochemical profiles. The Jaccard index is calculated as follows: Jaccard = A/(A + B + C), where A is the number of compounds shared by both groups, B is the number of compounds present only in the first group, and C is the number of compounds present only in the second group.45,46 This approach provides a robust similarity measure, particularly for phytochemical data where the presence or absence of compounds is more informative than their quantities. Combining the UPGMA and Jaccard similarity coefficient provided reliable and interpretable results. This approach also aligns with previous research on phytochemical classification, further supporting its suitability for this type of analysis. 46
Finally, the analysis was carried out using the PAST 4 Program, which generated a dendrogram to visualize the relationships among the species. The dendrogram represented how these species group together based on their shared phytochemical traits. To enhance the clarity of the presentation, the resulting dendrogram was further refined in Pixelmator Pro software, where species names were added for ease of interpretation and improved visualization.
Analysis and Insights
Volatile Oil Components of Zingiber Species
In previous studies, gas chromatography-mass spectrometry (GC-MS) has been routinely used to identify volatile compounds, mainly EOs, from Vietnamese Zingiber spp. Table 1 shows the EO components isolated from different parts of Zingiber species, including rhizomes, roots, pseudostems, stems/aerial parts, leaves, inflorescences and fruits.
Zingiber acuminatum Valeton
Zingiber acuminatum Valeton, commonly known as “Gừng Nhọn” in Vietnamese, is a native species of Borneo, Jawa, Vietnam, discovered in 1904.16,47,48 So far, no reports have noted the medicinal value of this plant. The GC-MS analysis identified 19 components in the rhizome oil of Z. acuminatum from Bach Ma National Park, Thua Thien Hue Province, Vietnam in July 2019. The rhizome oil components were mainly characterized by the presence of bornyl acetate, humulene, β-pinene, endo-borneol, fenchyl acetate, D-limonene, and β-caryophyllene. 16
Zingiber atroporphyreum Škorničk. & N.B. Nguyen (Z. atroporphyreus)
In 2015, a new Zingiber species from Vietnam, named Zingiber atroporphyreus, was discovered by Leong-Skornickova and colleagues.49–51 So far, there have been no reports that have noted the use values of Z. atroporphyreus. The chemical profiles of the EOs extracted from Z. atroporphyreus collected from Xuan Son National Park, Tan Son District, Phu Tho Province, Vietnam, have been reported. 17 The EOs of Z. atroporphyreus leaves and rhizomes mainly consist of monoterpene hydrocarbons (67.6% for leaves, 79.8% for rhizomes), followed by sesquiterpene hydrocarbons (27.0% for leaves, 13.8% for rhizomes). The quantitative amounts of oxygenated monoterpenes (2.3%-2.5%) and oxygenated sesquiterpenes (0.5%-1.2%) were low in the leaves and rhizome oils of Z. atroporphyreus. Accordingly, the leaf oil of Z. atroporphyreus were mainly characterized by the presence of β-pinene, α-pinene, β-elemene, sabinene, α-zingiberene, β-caryophyllene, and limonene, while the rhizome oil of this plant contained β-pinene, α-pinene, camphene, β-elemene, sabinene, and limonene, as its major components. 17
Zingiber castaneum Škorničk. & Q.B.Nguyen
Recently, Zingiber castaneum was described as a new species in the Zingiber genus by Leong-Skornickova and colleagues.50,52 Several research reports have been on the EO compositions obtained from Z. castaneum. The components of the EOs of four plant parts from Z. castaneum, such as leaves, stems, roots, and fruits collected from Vu Quang National Park, Ha Tinh Province, Vietnam, have been identified with forty-one, forty, thirty-eight, and thirty-five components, respectively. 18 In contrast, forty-three and fifty-one components were identified from the leaf and rhizome EOs of Z. castaneum collected from Pu Hoat Nature Reserve, Nghe An Province, Vietnam, respectively. 20 Accordingly, the major groups of the chemical composition from Z. castaneum EO were reported mainly by sesquiterpene hydrocarbons (73.0% for stems, 41.1% for leaves, 35.7% for fruits), monoterpene hydrocarbons (54.0% for roots, 49.2% for leaves), oxygenated monoterpenes (34.0% for stems), oxygenated sesquiterpenes (30.8% for fruits, 16.8% for stems), and amides (17.3% for fruits). 18 However, the sesquiterpene hydrocarbon group occurred in higher quantities in the leaves (64.9%) and rhizomes (66.2%) of Z. castaneum (Nghe An province), 20 compared with 41.1% for the leaves of Z. castaneum (Ha Tinh province). 18 Notably, monoterpene hydrocarbons were present in lower amounts in leaves (23.5%) and rhizomes (10.1%) 20 compared with a report by Huong et al. 19
The main constituents of the leaf oil were β-pinene and β-caryophyllene. 18 The leaf oil of Z. castaneum was mainly composed of β-pinene, α-pinene, β-caryophyllene, bicycloelemene, bicyclogermacrene, germacrene D, and limonene. In contrast, its stem oil contained β-caryophyllene, δ-cadinene, bicycloelemene, α-cubebene, trans-α-bergamotene, β-selinene, zerumbone, β-pinene, bicyclogermacrene, α-cedrol, and α-humulene as are major compounds. Additionally, the major constituents in Z. castaneum root oil were camphene, 1,8-cineole, linalool, δ-3-carene, α-pinene, sabinene, β-pinene, β-myrcene, bornyl acetate, and p-cymene, whereas (E)-nerolidol, (Z)-9-octadecenamide, trans-α-bergamotene, 1,8-cineole, β-caryophyllene, and linalool were the major constituents in the fruit oil. 18 From the EO of Z. castaneum rhizomes collected from Pu Hoat Nature Reserve, Nghe An Province, Vietnam, four-teen components, including sabinene, camphene, bicyclogermacrene, cis-β-elemene, germacrene D, α-pinene, α-humulene, β-pinene, γ-terpinene, δ-elemene, α-zingiberene, limonene, 1-epi-cubenol, and α-terpinene were identified as its major components. 20 In contrast, the major components of the leaf EO were bicyclogermacrene, germacrene D, cis-β-elemene, β-pinene, α-pinene, δ-elemene. 18 In another study, the major classes of compounds in the pseudo-stem oil were reported to be sesquiterpene hydrocarbons (66.2%), oxygenated sesquiterpenes (16.5%), monoterpene hydrocarbons (10.1%), and oxygenated monoterpenes (0.8%). The main components include bicyclogermacrene, cis-β-elemene, germacrene D, α-humulene, δ-elemene, α-zingiberene, β-pinene, and 1-epi-cubenol. 19
Zingiber cornubracteatum Triboun & K. Larsen
Zingiber cornubracteatum was first discovered in northern Thailand in 201453,54; Then it was found in Thanh Hoa, Nghe An, and Quang Binh Provinces, Vietnam, in 2019. 55 Macromorphologically, it is a robust tufted herb. Rhizome thick, creamy to light brown. Leafy shoots are erect, 1.8-2.6 m tall, with 20-23 leaves. The whole spike is reddish. The apex of bracts is curved with a hook-like appendage. It grows in shady places in rich soil along streams in hilly evergreen forests at altitudes of 800-1100 m. 53 Zingiber cornubracteatum is commonly known as “Gừng Lá Bắc Cựa” in Vietnamese. To date, there is no information about the medicinal use of this plant.
The leaf and rhizome EOs of Z. cornubracteatum from Khe Kem Waterfall, Pu Mat National Park, Nghe An Province, Vietnam were predominantly composed of monoterpene hydrocarbons (29.1% for leaves, 49.3% for rhizomes), sesquiterpene hydrocarbons (57.2% for only leaves), and oxygenated monoterpenoids (30.8% for only rhizomes but absent in leaf oils), followed by oxygenated sesquiterpenoids (9.9% for leaves, 10.1% for rhizomes), while the leaf and rhizome oils of this plant from Tri Le Commune, Que Phong District, Pu Hoat Nature Reserve, Nghe An Province, Vietnam possessed monoterpene hydrocarbons (30.2% for leaves, 35.1% for rhizomes), oxygenated monoterpenoids (51.4% for rhizomes), sesquiterpene hydrocarbons (24.0% for leaves), and oxygenated sesquiterpenoids (31.2% for only leaves but absent in rhizome oils) as their primary component classes. 28 The leaf EO of Z. cornubracteatum collected from Pu Mat National Park contained bicyclogermacrene (18.9%), β-pinene (18.8%), β-caryophyllene (13.9%), and germacrene D (13.7%) as the most dominant constituents, while the major oils of Z. cornubracteatum rhizomes included linalool, β-pinene, (E)-nerolidol, bornyl acetate, and myrcene, followed by notable amounts of 1,8-cineole, δ-3-carene, limonene, p-cymene, and camphene. 28 Similarly, α-pinene (5.1-14.5%) and β-pinene (14.8-20.1%) were found as the major constituents in the leaf and rhizome oils of Z. cornubracteatum collected in Pu Hoat Nature Reserve. However, (E)-nerolidol, β-caryophyllene, and bicyclogermacrene were found in the leaf oil, while linalool, 1,8-cineole, and borneol were noted as the major components in the rhizome oil. 28
In addition, the leaf, stem, and rhizome of Z. cornubracteatum collected from Xuan Ly Commune, Nhu Thanh District, Ben En National Park, Thanh Hoa Province, Vietnam have also been reported for their chemical constituents of EOs. Accordingly, the leaf, stem, and rhizome oils of this plant were mainly composed of monoterpene hydrocarbons (81.9%, 81.2%, and 77.8%, respectively), followed by sesquiterpene hydrocarbons (11.8% for leaves, 13.7% for stems) and oxygenated monoterpenoids (8.8% for rhizomes). Notably, α-pinene (9.8%-10.1%) and β-pinene (33.1%-67.3%) were the main constituents in the Z. cornubracteatum leaf, stem, and rhizome oils from Ben En National Park, Thanh Hoa Province. 28
Zingiber collinsii Mood & Theilade
Zingiber collinsii Mood & Theilade (Vietnamese name: “Gừng Lá Sọc”) is commonly known as an ornamental plant and is used as a food flavoring. This species is native to Vietnam and Laos.56–58 This species has only been used in Vietnam to repel mosquitoes and insects. In addition, the EO from this species is also used as a flavor in food. 11
Morphological characteristics of Z. collinsii are determined by its perennial rhizomatous herb, 0.7-1.0 m tall; the glabrous leaves, which are silvery along the veins above and burgundy below; inflorescences with orange or pink bracts and rounded apex; shorter bracteoles (3.0 × 1.5 cm); flower 5.0-6.5 cm long; floral tube ca. 3.5 cm long, narrowly funnel-shaped, slightly curved in upper part; dorsal corolla lobe oblong, with conspicuous raised longitudinal veins, 2.3-2.5 × 1.0-1.2 cm wide; lateral corolla lobes narrowly lanceolate, with conspicuous raised longitudinal veins, 1.8-2.0 cm × 5-6 mm; labellum triangular, ca. 2.0 × 1.0 cm, cream yellow, tessellated with dark purple.58,59
Also, some bioactive compounds, including zerumbone (1), scopoletin (2), quercetin (3), rutin (4), 5-(hydroxymethyl)furfural (5), bisdemethoxycurcumin (6), and demethoxycurcumin (7), were isolated and identified from Z. collinsii rhizomes. 21
The classes of compounds present in the rhizome oil of Z. collinsii collected from Pu Mat National Park, Nghe An Province, in July 2012 were monoterpene hydrocarbons (88.4%), sesquiterpene hydrocarbons (2.0%), oxygenated monoterpenes (1.5%), oxygenated sesquiterpenes (0.5%), and others (4.5%) among total EO (96.9%). 60 In contrast, the rhizome oil of Z. collinsii collected from Thuong Nhat Commune, Nam Dong District, Thua Thien Hue Province in September 2018 included monoterpene hydrocarbons (58.3%), oxygenated monoterpenes (10.9%), oxygenated sesquiterpenes (21.1%), and sesquiterpene hydrocarbons (7.4%) as the classes of compounds present in this total oil (97.7%). 11 The major components of Z. collinsii rhizome oil (Nghe An) were α-pinene, β-pinene, and limonene, 60 whereas camphene (22.5%), β-pinene, α-pinene, humulene oxide II, limonene, and caryophyllene oxide were the representatives of the main components in Z. collinsii rhizome oil (Thua Thien Hue). 11 Two constituents with significant amounts of rhizome EOs from Thua Thien Hue, namely humulene oxide II and caryophyllene oxide, were absent in rhizome oil from Nghe An. Furthermore, the α-pinene content in the Nghe An rhizome oil sample (50.2%) was higher than that in the Thua Thien Hue oil sample (9.0%), whereas the camphene content in the Nghe An oil sample (2.3%) was lower than that in the Thua Thien Hue oil sample (22.5%).
Compared with Z. collinsii rhizome EOs, the leaf EOs differ in the oil components’ content. Briefly, monoterpene hydrocarbons (49.0%), sesquiterpene hydrocarbons (36.3%), oxygenated sesquiterpenes (7.6%), oxygenated monoterpenes (1.8%), non-terpenoids (1.7%), and diterpenes (1.6%) were the classes of components present in the Z. collinsii leaf oil collected from Thua Thien Hue Province, Vietnam. α-Pinene, β-caryophyllene, β-pinene, bicyclogermacrene, and cis-β-elemene were the major components found in leaf oil from Z. collinsii. 11 Notably, the bicyclogermacrene, cis-β-elemene, β-caryophyllene, and α-pinene contents in leaf oil were higher than in the rhizome oil sample. In contrast, the camphene content in rhizome oil was higher than that in the leaf oil sample. Particularly, humulene oxide II (9.0%) in the rhizome oil was absent in this leaf oil.
Zingiber densissimum S.Q. Tong & Y.M. Xia
In 1987, Zingiber densissimum was first discovered by Tong and Xia in China.61,62 It was then found in Thailand (2014), 53 Laos (2018), 63 and Myanmar (2019). 64 Recently, Z. densissimum has been recorded in Lam Dong Province, Vietnam, in 2023. 65 Z. densissimum is commonly known as “Duo Mao Jiang” (多毛姜) in Chinese 62 and “Gừng Nhiều Lông” in Vietnamese. It is a perennial or rhizomatous herb, reaching a height of 40-80 cm. The leaf base narrowly attenuates. Inflorescences arise from rhizomes, with peduncles attached below ground level. Its inflorescence is often covered with a gelatinous substance to keep the moisture for its delicate white flowers.53,63,64
The main constituents of EOs from Z. densissimum rhizomes collected from Lac Duong District, Lam Dong Province, Vietnam are mainly composed of monoterpene hydrocarbons (85.4%), followed by oxygenated sesquiterpenes (3.19%), sesquiterpene hydrocarbons (2.35%), diterpens (2.17%), and oxygenated monoterpenes (1.36%). Accordingly, the rhizome oil of Z. densissimum contained β-pinene, β-phellandrene, and α-pinene as their major constituents. 22
Zingiber eberhardtii Gagnep.
Zingiber eberhardtii is an EO plant commonly known as “Gừng Eberhardt” in Vietnamese.14,66 It is endemic to Vietnam and was first reported in 1907. 66 It can be found in Ninh Binh, Kon Tum, and Lam Dong Provinces. 67 There is little information about the medicinal uses of Z. eberhardtii, only that the rhizome of this species is used in Vietnamese folk medicine to treat rheumatism and dysentery. 12
The major constituents of Z. eberhardtii rhizome oils from Lam Dong Province, Vietnam, were mainly characterized by the predominance of oxygenated monoterpenoids (76.7%), followed by monoterpene hydrocarbons (12.3%), non-terpenic components (5.1%), and oxygenated sesquiterpenoids (2.1%), which accounted for 96.3% of the constituents. Notably, the rhizome EOs of this plant contained linalool and 1,8-cineole as the most dominant constituents, followed by notable amounts of cis-linalool oxide, trans-linalool oxide, β-pinene, camphene, (3Z)-hexenyl butanoate, and borneol. 23
Zingiber gramineum Noronha ex Blume (Synonym: Dymczewiczia graminea (Noronha ex Blume) Horan., Z. gramineum var. validior K.Schum.)
Zingiber gramineum Noronha ex Blume, commonly known as “Grassy Ginger, Palm Ginger, or Tennis Ball Ginger” in English, “Gừng Lúa, or Ngải Trặc” in Vietnamese, 68 and its synonym “Dymczewiczia graminea (Noronha ex Blume) Horan., Z. gramineum var. validior K.Schum.”, is a native species of Cambodia, Jawa, Myanmar, Sumatera, Thailand, and Vietnam.69,70 In Vietnam, the crushed rhizome of this species is used in folk medicine to treat sprains and dislocations. 14
In a study by Le et al, 24 the compositions of Z. gramineum EOs are mainly composed of sesquiterpene hydrocarbons, followed by monoterpene hydrocarbons, oxygenated monoterpenes, aromatic esters, oxygenated sesquiterpenes, and diterpenes. The EOs of leaves, stems, and roots of Z. gramineum were collected from Pu Mat National Park, Nghe An Province, Vietnam, and analyzed through GC-MS and gas chromatography flame ionization detection (GC-FID) techniques. Accordingly, the major components of the Z. gramineum leaf EO included zingiberene, β-cubebene, β-sesquiphellandrene, β-elemene, bicycloelemene, β-pinene, β-bisabolene, and α-pinene. Meanwhile, the stem oil of Z. gramineum had benzyl benzoate, β-elemene, α-selinene, β-pinene, β-selinene, terpinen-4-ol, δ-cadinene, bicycloelemene, α-humulene, and β-caryophyllene as their major constituents. Moreover, γ-terpinene, α-terpinene, terpinen-4-ol, 1,8-cineole, β-pinene, α-terpinolene, α-pinene, and β-myrcene have been reported as the common constituents in the EO isolated from Z. gramineum roots. 24 For the first time, Le et al 24 reported thirty-four, twenty-five, and thirty-eight volatile compositions in the EOs of Z. gramineum leaves, stems, and roots, respectively. 24 To our knowledge, there are no further reports on the chemical composition and pharmacological effects of the EO of Z. gramineum collected from Vietnam and elsewhere.
Zingiber mekongense Gagnep.
Zingiber mekongense Gagnep. is also known as “Gừng Mê Kông” in Vietnamese. 71 It is native to Assam, Cambodia, Laos, Myanmar, Thailand,13,64,72 and Vietnam. 71 This plant can reach up to 15.0 m tall with distinguishing features of apex inflorescence rounded and labellum pale yellow mixed red dots, spike with closed bracts.13,53,64,71 This species usually grows primarily in the wet tropical biome. Local people use young inflorescences as food and vegetables. Whole plants are used as ornamental. In traditional medicine, rhizomes are used for stomachaches. 13
Z. mekongense collected from Pu Mat National Park, Nghe An Province, Vietnam, has been reported to possess a diverse chemical constitution in the leaf, stem, rhizome, and fruit oils from this species. Accordingly, the EOs of Z. mekongense leaf (31 components accounting for 98.1%), stem (44 constituents representing 87.0%), rhizome (43 constituents representing 89.9%), and fruit (46 components amounting to 87.0%) mainly consist of monoterpene hydrocarbons (60.4% for leaves, 30.1% for rhizomes, 19.8% for stems, 17.8% for fruits) and sesquiterpene hydrocarbons (54.1% for stems, 53.9% for fruits, 39.3% for rhizomes, 32.7% for leaves), followed by oxygenated sesquiterpenes (15.1% for rhizomes, 10.7% for fruits, 10.0% for stems, 3.8% for leaves). 25 Notably, the leaf oil did not detect oxygenated monoterpenes, aliphatic alcohols, and fatty acids. At the same time, diterpenes were absent in the fruit oil. Also, aliphatic alcohols and fatty acids were not detected in the stem and rhizome oils. 25 The main constituents of the leaf oil (namely, β-pinene, cis-β-elemene, α-pinene, β-caryophyllene, and α-humulene), stem oil (namely, cis-β-elemene, β-caryophyllene, β-pinene, α-humulene, α-pinene, and (E)-nerolidol), rhizome oil (namely, β-pinene, cis-β-elemene, β-caryophyllene, α-zingiberene (E)-nerolidol, and α-pinene), and fruit oil (namely, β-caryophyllene, cis-β-elemene, β-pinene, (E)-nerolidol, and α-pinene), were identified in Z. mekongense. 25
Also, some bioactive compounds, including (3S,5S)-3,5-diacetoxy-1,7-bis(3,4,5-trimethoxyphenyl)heptane (8), docosyl trans-ferulate (9), (1S,2S,4S)-p-menthan-1,2,4-triol (10), 5αH-eudesmane-4α,11-diol (11), 5αH-eudesmane-4β,11-diol (12), 4α,10β-dihydroxy-1βH,5αH-guaia-6-ene (guaianediol) (13), (+)-galanolactone (14), (E)-labda-8(17),12(13)-dien-1 516-olide (15), labda-8(17),13(14)-dien-15,16-olide (16), 3,5-dihydroxy-7,4′-dimethoxyflavone (17), and 3,5,3′-trihydroxy-7,4′-dimethoxyflavone (18) were isolated from Z. mekongense rhizomes collected from Trat Province, Thailand. 73 Among these, compounds 8 (IC50 = 119.6 μM, EC50 = 60.9 μM), 11 (IC50 = 630.7 μM, EC50 = 277.1 μM), 12 (IC50 > 520 μM, EC50 = 177.2 μM), 13 (IC50 > 1048.8 μM, EC50 = 266.8 μM), 14 (IC50 = 315.6 μM, EC50 = 26.1 μM), 16 (IC50 = 368.3 μM, EC50 = 86.6 μM), 17 (IC50 > 795.4 μM, EC50 = 43.3 μM), and 18 (IC50 > 757 μM, EC50 = 79.9 μM) exhibited anti-HIV-1 activities in the anti-syncytium assay using ΔTat/revMC99 virus and 1A2 cell line system. In particular, only compounds (14) and (18) were found active in the HIV-1 reverse transcriptase assay with IC50 of 211.3 μM and 96.6 μM, respectively. 73
In a study by Mizuno et al, 74 seven anthocyanins, namely delphinidin 3-O-glucoside (19), delphinidin 3-O-rutinoside (20), cyanidin 3-O-glucoside (21), cyanidin 3-O-rutinoside (22), petunidin 3-O-rutinoside (23), peonidin 3-O-rutinoside (24), and malvidin 3-O-rutinoside (25), were isolated and identified from the reddish leafy stems and rhizomes of Z. mekongense cultivated in the Tsukuba Botanical Garden, Ibaraki Pref., Japan. 74
Zingiber monophyllum Gagnep.
Zingiber monophyllum Gagnep. is commonly known as “Gừng Một Lá” in Vietnamese. 14 This species usually grows primarily in the wet tropical biome. Z. monophyllum is native to Vietnam and Laos.67,75 In a study by Giang et al, 76 from the ethyl acetate fractionated extract of Z. monophyllum rhizomes, nine compounds were determined by GC-MS analysis, namely, (E)-labda-8(17),12-diene-15,16-dial, spathulenol, neointermedeol, globulol, ambrial, alloaromadendrene, τ-cadinol, aromadendrene oxide-(2), and (E)-15,16-dinorlabda-8(17),11-dien-13-one. 76
For Z. monophyllum EOs, twenty-three and seventeen components were detected in the rhizome and leaf oils, accounting for 90.9% and 91.8% of these total EOs, respectively. The classes of compounds of Z. monophyllum EOs collected from Nam Dong District, Thua Thien Hue Province, in September 2021 were monoterpene hydrocarbons (52.7% for rhizomes, 33.4% for leaves), oxygenated monoterpenes (14.5% for rhizomes, 11.8% for leaves), sesquiterpene hydrocarbons (9.5% for rhizomes, 10.7% for leaves), oxygenated sesquiterpenes (11.7% for rhizomes, 2.1% for leaves), and other components (2.5% for rhizomes, 33.7% for leaves). The major components in rhizome oil were β-pinene, borneol, spathulenol, α-pinene, iso-acorone, and myrtenal, whereas β-pinene, dihydroedulan I, n-hexadecanol, α-copaene, myrtenal, α-cis-bergamotene, and borneol, as the major component in the leaf oil. 26 Notably, allyl isovalerate, camphene, (E)-β-ocimene, endo-fenchol, δ-elemene, ylangene, β-caryophyllene, α-humulene, δ-cadinene, caryophyllene oxide, bornyl acetate, 1-epi-cubenol, and iso-acorone were components only found in the rhizome oil. In contrast, dihydroedulan I, 5-methyl-3-heptanone, 2-acetoxyhexane, α-copaene, α-cis-bergamotene, n-tetradecanol, and n-hexadecanol were compounds only found in the leaf oil. 26
Zingiber magang N.S.Lý & Škorničk. and Zingiber tamii N.S.Lý & Škorničk.
In 2021, two new Zingiber species, named Zingiber magang N.S.Lý & Škorničk. and Zingiber tamii N.S.Lý & Škorničk., have been recorded from central Vietnam (Quang Ngai Province).77–79 The rhizome oil of Z. magang from Quang Ngai, Vietnam had (E)-nerolidol, α-selinene, caryophyllene oxide, β-caryophyllene, neo-intermedeol, selina-5,11-diene, and myrtenyl acetate as its dominant components, while its leaf oil contained notable amounts of β-pinene, (E)-nerolidol, β-phellandrene, trans-muurola-4(14),5-diene, α-selinene, dihydroedulan, neo-intermedeol, and caryophyllene oxide. Notably, the significant chemical constituents, such as β-pinene, α-pinene, β-phellandrene, linalool, pinocarvone, kessane, selina-4,11-diene, and γ-amorphene were present only in the leaf oil, whereas selina-5,11-diene, γ-bicyclofarnesal, γ-bicyclohomofarnesal were only identified in the rhizome oil with significant content. 27 Also in the report of Huong et al, β-pinene (53.8% and 55.4%) was the leaf and rhizome EO constituents of Z. tamii (Quang Ngai, Vietnam), followed by sabinene (12.3% and 12.5%), and α-pinene (4.8% and 5.0%), respectively. 27
Zingiber neotruncatum T.L. Wu, K. Larsen & Turland (Synonym: Z. truncatum S.Q. Tong)
Zingiber neotruncatum T.L.Wu, K.Larsen & Turland (Syn., Zingiber truncatum S.Q.Tong) is commonly known as “Jie Xing Jiang” (截形姜) in China 80 and “Gừng Lá Mới” or “Gừng Cắt Cụt” in Vietnam. 28 Z. neotruncatum is reported to be native to China, Thailand, Myanmar, India, and Laos.53,81–83 Recently, it has also been found in Vietnam. 84 This species is characterized by a perennial herb, growing in bushes 70-180 cm high. The rhizome is aromatic, 1.5-2.0 cm, yellow, with many roots. The pseudostem is about 1.0-1.5 m, purple toward the base, green as it grows higher, and hairy. The leaves are 10-35, dark green, sessile, with long lanceolate blades, 30-45 × 3.5-5.8 cm, pointed at the tip, obovate at the base, hairy at the base of the leaf, and along the veins on the underside of the leaf.53,80,84
Although Z. neotruncatum (Z. truncatum) has been recorded since 2000, there is no information on the medicinal value of this species to date. The abundant chemical classes in the EO of Z. neotruncatum rhizomes (Dong Van Commune, Que Phong District, Pu Hoat Nature Reserve, Nghe An Province, Vietnam) were oxygenated monoterpenoids (84.7%), monoterpene hydrocarbons (7.3%), sesquiterpene hydrocarbons (3.6%), oxygenated sesquiterpenoids (1.8%), and others (0.5%), which were identified via the GC-MS analysis. The main bioactive chemical constituents of the fresh rhizome EO of Z. neotruncatum were perillene, geranial, neral, and β-pinene. 28
Zingiber nitens M.F.Newman
Zingiber nitens M.F. Newman is a new species in the flora of Vietnam, found in 2017 by Hung and colleagues. 85 It is also found in Laos. 86 There is no readily available information on the medicinal uses of Z. nitens in traditional or folk medicine systems.
The major constituents of Z. nitens EOs are mainly composed of sesquiterpene hydrocarbons (63.0% for stems, 52.6% for leaves, and 30.8% for roots), monoterpene hydrocarbons (41.6% for roots, 23.0% for leaves, and 19.8% for stems), and oxygenated sesquiterpenes (16.9% for leaves), followed by oxygenated monoterpenes (14.2% for roots). 29 Thirty-six, forty-four, and forty-one chemical components were identified in the EOs of leaves, stems, and roots of Z. nitens collected from Pu Mat National Park, Nghe An province, Vietnam. 29 In contrast, the content of oxygenated sesquiterpenes (3.3%) in Z. nitens leaf EO was low, with a total of forty-three components identified in this oil, as Huong et al reported. 20 In addition, the main groups of Z. nitens rhizome EO are mainly composed of oxygenated monoterpenes (86.5%), followed by monoterpene hydrocarbons (10.2%), with seventeen components identified in this oil. 20 Notably, the most abundant constituents of Z. nitens leaf, stem, and root oils were δ-elemene and sabinene, followed by notable amounts of β-elemene, bicyclogermacrene, α-pinene, γ-elemene, and limonene. 29 In addition, the leaf oil of Z. nitens collected from Pu Hoat Nature Reserve, Nghe An Province, Vietnam was found to contain β-pinene, α-pinene, bicyclogermacrene (7.0%), α-zingiberene (6.4%) and germacrene D (4.7%) as dominant constituents. 20 In contrast, δ-elemene, β-pinene, β-elemene, bicyclogermacrene, germacrene D, ledol, endo-1-bourbonanol, and γ-elemene were the major compounds in the sample from Pu Mat National Park, Nghe An Province, Vietnam. 29 Moreover, Z. nitens rhizome EO was reported to be rich in terpinen-4-ol (77.9%). 20 Other components, such as γ-terpinene, cis-p-menth-2-en-1-ol, α-terpineol, trans-p-menth-2-en-1-ol, o-cymene, and trans-piperitol, were also found in this EO. 20
Zingiber nudicarpum D.Fang
Zingiber nudicarpum D.Fang is locally known as “Guang Guo Jiang” (光果姜) in Chinese 87 and “Gừng Lá Sáng Bóng” or “Gừng Quả Trần” in Vietnamese. 28 It is a widespread species ranging from South China, Laos, and Vietnam to Thailand.88,89 Recently, the volatile oil constituents of Z. nudicarpum have been reported.28,30 The leaves, roots, rhizomes, stems, and fruits of Z. nudicarpum contained a high presence of monoterpene hydrocarbons (16.0%-84.8%, except Z. nudicarpum stem oil from Pu Hoat), sesquiterpene hydrocarbons (20.0%-65.1%, except Z. nudicarpum stem oil from Pu Hoat), and oxygenated sesquiterpenes (11.6%-45.7%, except Z. nudicarpum stem oil from Pu Hoat). Notably, Z. nudicarpum stems and rhizomes from Nam Dong were also characterized by the predominance of oxygenated monoterpenoids (25.3%-34.8%).28,30 Briefly, Z. nudicarpum leaf EOs (Pu Hoat, Nam Dong, Bach Ma) were rich in α-pinene (2.4%-10.9%), β-pinene (0.7%-34.0%), in addition to the sesquiterpene hydrocarbons β-caryophyllene (6.4%-24.3%), α-humulene (2.1%-6.4%), germacrene D (0.6%-6.5%), and bicyclogermacrene (3.3%-16.1%). However, the report (in 2019) 30 found no β-caryophyllene or germacrene D. Still, large concentrations of cedrol (14.8%) and β-eudesmol (13.8%) in this leaf oil, which was not found in the study in 2020. 28 The Pu Hoat stem EO had a high concentration of β-caryophyllene (52.6%), α-pinene (18.7%), and β-pinene (58.3%) as dominant constituents. Moreover, α-pinene and β-pinene were the major components in the rhizome EO sample from Nam Dong.28,30
Zingiber ottensii Valeton
Zingiber ottensii Valeton is commonly known as “Gừng Ottensi” in Vietnam 28 and “Phlai Dum” or “Plai Dam” in Thailand.46,64,89,90 Macromorphologically, Z. ottensii is a plant growing up to 2.0 m tall, characterized by a dark purple inside rhizome, 3-10 leaf shoots per clump, spike ellipsoid or cylindric, and labellum yellow with brown mottled.64,91 It is widely cultured in some countries, such as Thailand, Malaysia, Indonesia, Laos, and Vietnam.64,91–93
Z. ottensii has a diverse role in herbal medicine, commercial cultivation, rituals, and as an ornamental plant.46,94 Z. ottensii has been used as a traditional medicinal herb for treating various diseases in many countries. In Malaysia, a poultice made from the leaves and rhizomes is applied to the body for postpartum care and to treat backaches or lumbago. 95 The juice extracted from the rhizomes of this plant has been used as Thailand's traditional remedy to treat gastrointestinal ailments and digestive disorders, such as peptic ulcers, stomachaches, and constipation, as well as myalgia, sprains, bruising or contusions, and wounds. Moreover, the EO of rhizomes has been applied as a topical agent for Thailand's traditional massage.36,37,90 In Indonesia, Z. ottensii has been used as postpartum medicine and to cure itching, pain, fever, gout, and cough. 33
Moreover, the crude extracts of Z. ottensii exhibited anticancer, 36 antidiabetic, 96 and antimicrobial properties. 97 Also, several novel compounds, namely four new terpenoids and a diarylheptanoid, including 1,10,10-trimethylbicyclo[7,4,0]tridecane-3,6-dione (26), (E)-14-hydroxy-15-norlabda-8(17),12-dien-16-al (27), (E)-labda-8(17),12,14-trien-15(16)-olide (28), (E)-14,-15,16-trinorlabda-8(17),11-dien-13-oic acid (29), and rel-(3R,5S)-3,5-dihydroxy-1-(4-hydroxy-3-methoxyphenyl)-7-(3,4-dihydroxyphenyl)heptane (30), along with some other compounds, such as zerumbone (31), (E)-8(17),12-labdadiene-15,16-dial (31), zerumin A (33), coronarin B (34), coronarin D (35), zerumbone epoxide (36), eudesmane-4R,11-diol (37), 3,4′-O-dimethyl (38), 3,7,4′-O-trimethyl kaempferol (39), eicosyl ferulate (40), 5-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-7-(4-hydroxyphenyl)heptan-3-one (41), kaempferol 3-O-(2,4-O-diacetyl)-R-L-rhamnopyranoside (42), kaempferol 3-O-(3,4-O-diacetyl)-R-L-rhamnopyranoside (43), kaempferol 3-O-R-L-rhamnopyranoside (44), kaempferol 3-O-(2-O-acetyl)-R-L-rhamnopyranoside (45), kaempferol 3-O-(3-O-acetyl)-R-L-rhamnopyranoside (36), 98 and zingipain (47), 97 were isolated from Z. ottensii rhizomes. Notably, compound (30) had a stronger 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability than L-ascorbic acid and α-tocopherol with IC50 values of 24.0, 35.6, and 37.5 µM, respectively. 98
Z. ottensii has been recorded to possess diverse chemical constituents in the EOs from its different plant parts collected from Thailand, Malaysia, Indonesia, and Vietnam. In Vietnam, the major components of Z. ottensii leaf EOs were mainly characterized by the predominance of sesquiterpene hydrocarbons (60.5%) and monoterpene hydrocarbons (25.3%). In contrast, the major components of rhizome EOs (collected from Tri Le Commune, Que Phong District, Pu Hoat Nature Reserve) were monoterpene hydrocarbons (54.1%), followed by oxygenated monoterpenes (24.8%) and oxygenated sesquiterpenoids (15.9%). 28 In Thailand, the major constituents of Z. ottensii collected from Chiang Mai, August 2014, are mainly composed of monoterpene hydrocarbons (46.51%), followed by oxygenated monoterpenes (29.11%), sesquiterpene hydrocarbons (18.23%), and oxygenated sesquiterpenes (4.67%). 35 In contrast, oxygenated sesquiterpenes (39.2%) and sesquiterpene hydrocarbons (20.0%) were the major constituents of Z. ottensii rhizome EOs collected from Sabah Agricultural Park (Tenom), East Malaysia. 32
In Vietnam, sabinene, terpinen-4-ol, zerumbone, and β-pinene dominated the rhizome EO component of Z. ottensii (April 2019), followed by γ-terpinene, 1,8-cineole, α-humulene, and α-terpinene. 28 In comparison, the rhizome EO of Z. ottensii from Chiang Mai, Thailand (June 2019 and March 2020) was previously reported to contain zerumbone, sabinene, terpinen-4-ol, α-humulene, β-pinene, and thymene,36,37 along with zerumbone, terpinen-4-ol, p-cymene, sabinene, α-humulene, and β-pinene as the main components in the rhizome oil collected from Petchaburi, Thailand (March 2000). 34 Similarly, sabinene, terpinen-4-ol, humulene, β-pinene, α-pinene, γ-terpinene, and 1,8-cineole were major components found in the rhizome oil of Z. ottensii (Chiang Mai, Thailand, in September 2014). 35 Notably, samples collected from Chiang Mai, Thailand (June 2019 and March 2020) and Petchaburi, Thailand (March 2000) revealed zerumbone as the major component, while samples collected from Chiang Mai, Thailand (September 2014) did not. Additionally, the EO obtained from the Z. ottensii rhizome grown in Johor, Malaysia (1994) was dominated by zerumbone, terpinen-4-ol, α-humulene, sabinene, γ-terpinene, β-pinene, α-terpinene, and 1,8-cineole, 31 whereas zerumbone, α-humulene, sabinene, and terpinen-4-ol were the main compounds in the rhizome EOs of Z. ottensii from Sabah Agricultural Park (Tenom), East Malaysia (August 2004). 32 Also, the major abundant component of Z. ottensii rhizome oil from Manoko Research Garden, Bandung, West Java, Indonesia (February 2017) consists of terpinen-4-ol, zerumbone, sabinene, 1,8-cineole, γ-terpinene, α-terpinene, β-pinene, α-terpineol, and α-humulene. 33 Notably, terpinen-4-ol content in rhizome EOs (15.67%-17.1%) from Vietnam, Johor-Malaysia, Chiang Mai-Thailand, and Indonesia had higher content than that in rhizome EOs (3.16%-11.17%) from Sabah-Malaysia and Petchaburi-Thailand. On the contrary, the zerumbone content (12.5%-14.23%) of rhizome EOs from Pu Hoat-Vietnam and Bandung-Indonesia was lower than that of rhizome EOs (25.63%-40.14%) from Malaysia and Thailand.
The major EO components of Z. ottensii leaves from Pu Hoat Nature Reserve, Vietnam included β-caryophyllene, β-pinene, trans-β-elemene, α-copaene, and α-humulene as its main constituents. 28 The leaf oil of Z. ottensii from Bandung, Indonesia was mainly composed of β-caryophyllene, trans-β-elemene, zerumbone, 1,5-cyclodecadiene, α-humulene, α-copaene, and β-pinene. 33 Particularly, the concentration of β-pinene in the Z. ottensii leaf oil from Vietnam (17.1%) was higher than that in the leaf oil from Indonesia (3.15%). Surprisingly, zerumbone and 1,5-cyclodecadiene were not found in the leaf oil of this species from Vietnam.
Zingiber pellitum Gagnep.
Zingiber pellitum Gagnep. is commonly known as “Gừng Bọc Da” in Vietnam. This species was first recorded in Cambodia, Laos, Thailand, and Vietnam.63,99–101 Z. pellitum is a plant less than 1.0 m in height. Leaves sessile with ligule 7.0 mm; leaf blades long, lanceolate, white, narrow, long hairs, and pointed tips. The inflorescences grow at the ends of the apexes, spherical or ovoid, curved downward, and have many hairs. Bracts broadly ovate, 25-30 mm; bracteoles 25 mm. Labellum yellow with reddish patches at the margin; calyx 20 mm. The fruit is spherical or ovoid. The seeds are numerous and dark brown, and the seed coat is white. 102
For Z. pellitum, 28, 56, 34, 45, 29, and 17 components were determined in the rhizome, 38 root, leaf, stem, 39 inflorescence, 41 and aerial part EOs, 40 representing 82.6%, 81.0%, 97.0%, 95.5%, 99.0%, and 97.38% of these total EOs, respectively. Monoterpene hydrocarbons (23.4% for leaves, 25.0% for stems, 12.1% for roots), oxygenated monoterpenes (3.8% for leaves, 4.0% for stems, 6.1% for roots), sesquiterpene hydrocarbons (66.2% for leaves, 50.7% for stems, 30.1% for roots), oxygenated sesquiterpenes (2.9% for leaves, 14.3% for stems, 30.9% for roots), and diterpenes (0.7% for leaves, 0.5% for stems, 1.8% for roots) were class compounds identified in the Z. pellitum leaf, stem, and root oils collected from Binh Chau, Phuoc Buu Nature Reserve, Ba Ria-Vung Tau Province, Vietnam. 39 The major components of the leaf EO were β-caryophyllene, β-pinene, α-pinene, α-humulene, and germacrene D. The stem EO consists of β-caryophyllene, β-pinene, α-humulene, caryophyllene oxide, α-pinene, and humulene epoxide II as the main constituents, while 9-epi-(E)-caryophyllene, humulene epoxide II, α-humulene, caryophyllene oxide, β-caryophyllene, cyperotundone, camphene, and α-pinene were major components detected in the Z. pellittum root oil. Notably, β-bourbonene, germacrene B, α-bisabolol, (Z)-ligustilide, cis-5-hydroxycalamenene, trans-sabinol, and terpinolene were found only in stem oils, whereas components such as γ-bicyclohomofarnesal, (E)-15,16-bisnorlabda-8(17),11-dien-13-one, cyperotundone, γ-bicyclofarnesal, α-calacorene, trans-calamenene, γ-cadinene, δ-amorphene, α-muurolene, β-selinene, β-chamigrene, γ-muurolene, 9-epi- β-caryophyllene, nardosina-7,9,11-triene, cyperene, theaspirane isomer 1, theaspirane isomer 2, bornyl acetate, geranial, menthol, camphor, cis-sabinol, tricyclene, and o-cymene were recorded only in the root oil. Additionally, the oil components found only in the leaves of this plant included β-phellandrene, (E)-β-ocimene, trans-anethole, and zingiberenol but were absent in stem and root oils. 39
Z. pellitum contained a high presence of sesquiterpene hydrocarbons (48.26%), monoterpene hydrocarbons (29.51%), and oxygenated sesquiterpenes (18.06%). β-Caryophyllene, α-pinene, cyclofenchene, 3-carene, sylvestrene (5.35%), β-pinene, zerumbone, cyclopropane, 1,1-dimethyl-2- (3-methyl-1, 3-butadienyl)-, caryophyllene oxide, cis-thujopsene (3.68%), γ-muurolene (3.02%), α-cadinol, and α-gurjunene were the main components in the fresh aerial part oil of Z. pellitum collected from Binh Chau-Phuoc Buu Nature Reserve, Bung Rieng Ward, Xuyen Moc District, Ba Ria-Vung Tau Province, Vietnam. 40
For Z. pellitum rhizome EOs (collected in Huong Son District, Ha Tinh Province, Vietnam), oxygenated monoterpenoids (45.4%) and monoterpene hydrocarbons (34.7%) were the major classes in the rhizome EOs, followed by sesquiterpene hydrocarbons (2.0%) and oxygenated sesquiterpenoids (0.5%). A significant percentage of terpinen-4-ol and p-cymene were identified in the rhizome oil. Sabinene and β-pinene were also the abundant components in this oil. 38 Compared with the EOs of other parts of this species,39,40 minor constituents like trans-sabinene hydrate, cis-sabinene hydrate, trans-p-menth-2-en-1-ol, α-terpineol acetate, terpinen-4-ol acetate, aristolochene, germacrene A, p-cymene, cis-piperitol, trans-piperitol, fenchyl acetate, and α-thujene were identified only in the rhizome EO. 38
By GC-MS analysis, 29 components (accounting for 99.0% of total oil) were detected in the inflorescence EOs of Z. pellitum, with sesquiterpene hydrocarbons (85.14%) as the main class of components, followed by monoterpene hydrocarbons (8.86%), oxygenated sesquiterpenes (4.13%), oxygenated monoterpenes (0.66%), aromatic compounds (0.55%), and others (0.13%) as the minor class of components. The major components in inflorescence oil included β-caryophyllene, α-humulene, β-pinene), and germacrene D. 41
Zingiber plicatum Škorničk. & Q.B.
Zingiber plicatum Škorničk. & Q.B. Nguyen is a native species of Vietnam described in 2015.50,51,103 It is a perennial rhizomatous herb, ca. 0.5-0.7 m tall. It is characterized by having an elliptic to broadly elliptic to obovate lamina, open flowers with prominently plicate leaves, a long ligule, and a peach-purple to purple labellum with an incised apex. 50 Until now, no report is available on the medicinal uses of Z. plicatum. The chemical profile of the EOs from Z. plicatum rhizomes is characterized by the predominance of monoterpene hydrocarbons (57.69%) and sesquiterpene hydrocarbons (28.98%), followed by oxygenated sesquiterpenes (5.68%) and oxygenated monoterpenes (1.7%) in very low amounts. The major volatile components of Z. plicatum rhizomes from Phu Tho Province, Vietnam included β-pinene, α-pinene, limonene, germacrene D, bicyclogermacrene, and δ-elemene. 42
Zingiber recurvatum S.Q. Tong & Y.M. Xia
Zingiber recurvatum S.Q.Tong & Y.M.Xia is commonly known as “Wan Guan Jiang” (弯管姜) in China 104 and “Gừng Lá Bắc Cong” in Vietnam. 28 Z. recurvatum was first recorded in southern Yunnan Province, China (1987),104–106 but has since been found in Vietnam and northern Laos.63,106–108 Z. recurvatum is characterized by pseudostems 2.0-3.0 m × 2.0-3.5 cm. Leaves sessile with ligule 2-lobed, 8-11 mm. Inflorescences red, ovoid or capitate, 7-9 × 6-7 cm; peduncle 3-5(−15) cm.104,105
For the chemical profile of Z. recurvatum (Tri Le Commune, Que Phong District, Pu Hoat Nature Reserve, Nghe An Province, Vietnam), 23 and 59 constituents were found in the leaf and rhizome EOs, accounting for 100% and 89.40% of the total EOs, respectively. 28 Monoterpene hydrocarbons (94.2%) and sesquiterpene hydrocarbons (31.0%) were the highest constituents in leaf and rhizome EOs, respectively. Specially, β-pinene and α-pinene were the major components in the leaf oil. Meanwhile, β-caryophyllene, bornyl acetate, α-humulene, bicyclogermacrene, β-pinene, caryophyllene oxide, zerumbone, linalool, and (E)-nerolidol were significantly abundant constituents in the rhizome oil. Notably, γ-bicyclofarnesal, 10-epi-γ-eudesmol, humulene epoxide II, (Z)-β-farnesene, bornyl acetate, linalool, and δ-3-carene were components found only in rhizome EO. 28
Zingiber rufopilosum Gagnep.
Zingiber rufopilosum Gagnep. is commonly known as “Gừng Lông Hung” in Vietnamese. It is only found in Vietnam and is mainly used to extract EOs.68,109 There are no documented reports on the use of this plant in traditional medicine.
The volatile chemical profiles of the EOs extracted from different parts of the Z. rufopilosum plant have been reported in previous research. 24 Accordingly, the composition of EOs in the leaves, stems, and roots of Z. rufopilosum was classified into relatively uneven chemical groups. Specifically, sesquiterpene was found the most in leaf EO (57.4%), followed by stem EO (40.4%) and root EO (19.7%). Meanwhile, oxygenated sesquiterpenes account for the most in stem EO (44.6%), followed by root EO (30.2%) and leaf EO (20.6%). On the contrary, monoterpenes and oxygenated monoterpenes were commonly observed in root EO (28.5% and 10.9%, respectively), followed by leaf EO (15.6% and 2.4%, respectively) and stem EO (8.9% and 0.4%, respectively). Diterpenes and other components account for small amounts of Z. rufopilosum EOs. The major components of leaf oil (namely, β-agarofuran, α-humulene, α-pinene, β-gurjunene, endo-1-bourbonanol, δ-cadinene, β-pinene, germacrene D, β-oplopenone, β-caryophyllene, and α-amorphene), stem oil (namely, α-cadinol, τ-muurolol, endo-1-bourbonanol, α-humulene, α-gurjunene, δ-cadinene, α-pinene, (E, E)-farnesol, β-agarofuran, β-pinene, and germacrene D), and root oil (namely, camphene, (E, E)-farnesol, α-pinene, bornyl acetate, β-pinene, limonene, τ-muurolol, (E, E)-α-farnesene, (E)-β-ocimene, and α-cadinol), were found in the Z. rufopilosum plant. 24
Zingiber rubens Roxb.
Zingiber rubens Roxb., a Zingiber species, has been found in Bangladesh, China, India, Myanmar, Thailand, and Vietnam.110,111 Z. rubens has been reported to possess a diverse chemical constituent in the EO from its root. The Z. rubens root oil collected from Nghe An, Vietnam (2010) comprised Z-citral, zingiberene, camphene, β-phellandrene, geraniol, and geranial as its main components. 43 Also, the rhizome EO obtained from Z. rubens grown in Lamphun, Thailand, contained zerumbone as the most abundant constituent, followed by β-copaene, isospathulenol, and germacrene B (3.64%). Two unusual components, namely 1,4,7,-cycloundecatriene, 1,5,9,9-tetramethyl-, Z,Z,Z- and cyclohexene, 4-pentyl-1-(4-propylcyclohexyl)-, were also found in this rhizome oil. 44
Zingiber skornickovae N.S. Lý
Zingiber skornickovae, commonly known as “Gừng Skornickovae” in Vietnamese, is a native species of Vietnam discovered in 2016.112,113 It is a rhizomatous herb, reaching a height of 1.1 m, forming small clumps with 1-4(−15) leafy shoots per clump. It is characterized by the remarkable features of having the larger, ovoid to narrowly ovoid spikes, 9-13 × 3.0-4.5 cm, the narrowly ovate and externally densely pubescent bracts with margins undulate and apices narrowly acuminate, loosely twisted, and the elliptic-obovate labellum, 28-34 × 18-22 mm, dark red-purple to purple-violet with pale yellow to whitish blotches.112,113
The rhizome oil of Z. skornickovae from Quang Ngai Province, Vietnam contained monoterpene hydrocarbons (49.7%) and sesquiterpene hydrocarbons (26.9%) as the primary components, as determined by GC-MS analysis. 23 The other chemical classes found in this oil were oxygenated sesquiterpenes (9.1%), non-terpenic compounds (7.1%), and oxygenated monoterpenes (5.0%). Of the 53 components identified in this oil, β-pinene and β-caryophyllene are the principal components. Several other compounds were also present in noteworthy concentrations with percentages greater than 3.0%, including benzyl benzoate, limonene, β-elemene, and cedrol. 23
Zingiber vuquangense N.S.Lý, T.H.Lê, T.H.Trinh, V.H.Nguyen & N.D.Do (Z. vuquangensis)
Zingiber vuquangense N.S.Lý, T.H.Lê, T.H.Trinh, V.H.Nguyen & N.D.Do (Vietnamese name: “Gừng Vũ Quang”), a new Zingiber species, was described and illustrated from Pu Hoat Nature Reserve (Nghe An Province), Vu Quang National Park (Ha Tinh Province), and Phong Nha-Ke Bang National Park (Quang Binh Province) of the North Central Coast region of Vietnam in 2018-2019.114–116 It is noteworthy that there is no information about the medicinal uses of this species until now.
Chemically, forty-five, thirty-one, thirty-eight, and forty-two compounds representing 91.5%, 94.5%, 95.0%, and 93.9% of oil contents were identified in Z. vuquangense leaves, stems, roots, and fruits collected from Vu Quang National Park, Ha Tinh Province, Vietnam, respectively. These comprised of mainly monoterpene hydrocarbons (47.4% for stems, 39.8% for fruits, 39.5% for leaves, 22.0% for roots), sesquiterpene hydrocarbons (34.3% for leaves, 30.0% for stems, 22.4% for fruits, 19.1% for roots), oxygenated monoterpenes (27.0% for fruits, 24.7% for roots), and oxygenated sesquiterpenes (22.6% for roots, 11.7% for stems, 9.2% for leaves). Amides are less common in leaf, root, and fruit oils and are absent in stem oil. Diterpenes are present only in leaf EO in very low amounts (0.5%). 18 The main constituents of the leaf oil were β-pinene, β-caryophyllene, α-humulene, α-pinene, and bicycloelemene. Bicyclogermacrene, (Z)-9-octadecenamide, (E)-nerolidol, and zerumbone were also present in sizeable amounts. The major components present in the stem oil were β-pinene, β-caryophyllene, α-humulene, α-pinene, camphene, elemol, zerumbone, and borneol. Notable compounds including bornyl acetate (20.9%), zerumbone, α-humulene, β-pinene, β-caryophyllene, camphene, and elemol were found in the root oil. Moreover, the EO was dominated by β-pinene, 1,8-cineole, α-pinene, β-caryophyllene, camphene, and α-thujone, which were the major components of the fruit oil. 18
In 2020, the chemical component profiles of the EOs extracted from Z. vuquangense collected from Nam Nhong Commune, Que Phong District, Pu Hoat Nature Reserve, Nghe An Province, Vietnam, have also been reported by Huong and colleagues. 28 The leaf and rhizome EOs of Z. vuquangense were both rich in monoterpene hydrocarbons (52.7% and 61.8%, respectively) and sesquiterpene hydrocarbons (34.1% and 15.4%, respectively). Moreover, the stem oil of this species was mainly composed of sesquiterpene hydrocarbons (49.1%) and oxygenated sesquiterpenoids (22.2%), followed by other components (9.5%). The major components in the leaf and rhizome oils were α-pinene and β-pinene. Meanwhile, β-caryophyllene and trans-β-elemene were also abundant in the leaf and stem oils of this species. 28 Notably, α-pinene, β-pinene, and β-caryophyllene were the major components found in both Z. vuquangense from Vu Quang National Park and Pu Hoat Nature Reserve. However, there are still some notable qualitative and quantitative differences between these two samples. Both bornyl acetate and zerumbone were the main compounds in the Z. vuquangense rhizome oil from the Vu Quang sample but were not presented in the Pu Hoat sample. Trans-β-elemene was observed in relatively small amounts in the leaf (0.8%), stem (0.5%), and rhizome (0.6%) oils from Vu Quang but was a main component in the sample from Pu Hoat.18,28
The difference in chemical components of these two samples may be due to the geographical location and/or the season of sample collection. Z. vuquangense from Vu Quang National Park was gathered in the rainy season, while the sample from Pu Hoat Nature Reserve was gathered in the dry season. 28
Moreover, EOs were mainly obtained by the hydrodistillation (HD) and steam distillation (SD) methods from different parts of 23 Zingiber species and produced pale-yellow EOs with yields of 0.043%-0.86% (v/w) for Zingiber species EOs (Table 1). According to Figures 2–4 and Table 1 with the main phytochemical features of Zingiber EOs, the EOs can be classified into the following groups: (1) monoterpene hydrocarbons and oxygenated monoterpenes; (2) sesquiterpene hydrocarbons and oxygenated sesquiterpenes; (3) and others (ester of carboxylic acid). The structures of the main constituents in EOs from different parts of some Zingiber species are presented in Figures 2, 3, and 4.
Major bioactive oxygenated sesquiterpenes detected in the EOs of Zingiber species.
Major bioactive sesquiterpene hydrocarbons detected in the EOs of Zingiber species.
Major bioactive monoterpene hydrocarbons, oxygenated monoterpenes, and other compounds detected in the EOs of Zingiber species.
The UPGMA Cluster Analysis and Jaccard’s Similarity Index
The UPGMA was used for clustering due to its straightforward calculation formula and its convenience for analyzing multi-sample similarity. UPGMA is well-suited for hierarchical clustering as it assumes a constant rate of evolution, which is appropriate for comparing phytochemical profiles. Additionally, its hierarchical approach facilitates the visualization of relationships among species, allowing for a clear interpretation of the similarity patterns. The dendrogram reveals the closest phytochemical similarities among species of Zingiber, beginning with the most similar species (Figure 5). The species Z. densissimum and Z. plicatum form the closest cluster, indicating they share the highest degree of phytochemical similarity. This close relationship suggests these species have highly comparable chemical compositions, possibly due to similar ecological environments or evolutionary adaptations. These species may produce similar secondary metabolites, influencing their medicinal or aromatic properties. Another group with significant similarity includes Z. mekongense and Z. vuquangense, which are clustered tightly together. Their proximity in the dendrogram suggests a high overlap in their phytochemical profiles, likely due to shared evolutionary pressures or adaptations to similar habitats. Slightly more distant but still relatively close in similarity are species such as Z. cornubracteatum and Z. nudicarpum. This grouping indicates moderate phytochemical similarity, suggesting these species share several chemical traits while still maintaining some distinct differences. Overall, the dendrogram shows varying levels of phytochemical similarity, with the closest clusters representing chemically similar species, while more distantly positioned species exhibit more unique phytochemical traits.
The dendrogram obtained from the closest phytochemical similarities among Zingiber species.
The dendrogram presented in the image illustrates the phytochemical similarity among Zingiber species, with the different parts of the plant (leaves, stems/aerial parts, rhizomes, roots, inflorescences, and fruits) being color-coded (Figure 6). The algorithm used is UPGMA. The similarity index is based on Jaccard, with a cophenetic correlation of 0.8132, indicating a reliable clustering outcome. The dendrogram (Figure 6) reveals phytochemical similarity among selected Zingiber species based on different plant parts, including leaves, rhizomes, roots, inflorescences, and fruits. The clustering patterns highlight both intra-specific and inter-specific relationships, with some plant parts from different species showing significant similarity, suggesting shared biochemical pathways within the genus. For instance, rhizomes from closely related species often cluster together, reflecting evolutionary conservation of key secondary metabolites. Interestingly, similarities across different plant parts, such as inflorescences and leaves, indicate functional or adaptive overlaps. These findings reinforce the taxonomic grouping within Zingiber and underline its phytochemical diversity. Such insights have practical implications for medicinal and economic applications, as chemically similar parts from different species may serve as substitutes, promoting sustainable utilization. This analysis also provides a foundation for further research integrating phytochemical, molecular, and ecological data to explore evolutionary relationships and adaptive traits within the genus.
The dendrogram in the image illustrates the phytochemical similarity among Zingiber species with the different parts of the plant.
In ethnomedicinal contexts, such a dendrogram serves as a key tool for understanding the chemical similarities among species and the appropriate plant parts to use for various medicinal purposes. The different plant parts contain distinct phytochemicals, which can be more or less effective depending on the intended use (eg, roots for digestive issues, rhizomes for anti-inflammatory properties). Therefore, identifying and utilizing the correct part of the plant for specific ethnomedicinal uses is crucial. The clustering patterns further highlight that some parts may have higher similarities in their chemical composition, reinforcing the importance of targeted harvesting to maximize medicinal efficacy. This analysis underscores the significance of selecting the appropriate plant part for the desired therapeutic application, ensuring that the right chemical compounds are used for the intended medicinal purpose. The dendrogram provides crucial insights into the phytochemical relationships among Zingiber species, highlighting the chemical similarities between various plant parts, including leaves, stems, rhizomes, roots, inflorescences, and fruits. The clustering patterns suggest that species together closely exhibit similar phytochemical profiles, indicating shared medicinal or nutritional properties. These similarities provide a valuable resource for ethnomedicinal practices, as species with high phytochemical likenesses may be used interchangeably for specific therapeutic purposes, optimizing the efficacy of plant-based treatments.
The dendrogram also highlights the necessity of selecting the correct plant part for traditional medicinal practices. Misidentifying or misusing a plant part could lead to reduced therapeutic effects or potentially harmful outcomes, as different organs contain distinct phytochemicals. The dendrogram's structure provides a guide for ensuring that the correct plant species and part are chosen, optimizing medicinal efficacy and safety in traditional medicine applications. Additionally, this information can be applied to the conservation and sustainable use of plant resources by identifying alternative species with similar chemical profiles to prevent overharvesting of preferred plants. Finally, the dendrogram reveals chemotaxonomic relationships, where phytochemical similarities often align with the taxonomic classification of Zingiber species. This reflects evolutionary adaptations where closely related species share similar bioactive compounds, further enhancing the understanding of the species’ medicinal value. By identifying clusters of species with similar phytochemical profiles, the dendrogram also offers the potential for discovering new applications for less-utilized species, expanding the knowledge base for medicinal plant use.
Biological Activities of Zingiber Oils
Accumulated studies have revealed that the secondary metabolites, especially EOs from different parts of Zingiber species, exhibited a broad spectrum of pharmacological effects, including antioxidant, antimicrobial, larvicidal, antidiabetic, anticancer, and cytotoxic effects. These biological activities have been summarized in Table 2 and presented in the following subsections.
Biological Activities and Cytotoxicity of Zingiber Species.
Antioxidant Effect
Only one recent report has investigated the antioxidant effects of EO extracted from Z. plicatum rhizomes. In this report, Van et al 42 demonstrated that the rhizome oil of Z. plicatum from Phu Tho, Vietnam (September 2023) had antioxidant effects through scavenging DPPH and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) free radicals. In the DPPH radical scavenging assay, the half maximal inhibitory concentration (IC50) value of the rhizome oil was found to be 84.53 ± 0.60 mg/mL, whereas the half maximal effective concentration (EC50) value in the ABTS scavenging model was 17.3 ± 0.01 mg/mL. The antioxidant activities of EOs were weaker than those of Trolox (IC50 = 0.038 mg/mL and EC50 = 0.1 mg/mL). The results showed that the EO had relatively mild antioxidant activity. 42
The antioxidant capacity of Z. plicatum rhizome EO is due to the presence of β-pinene, as reported in a recent study. 120 Accordingly, β-pinene exhibited antioxidant properties with IC50 values of 3116.3 ± 87.4 μg/mL, 2245.0 ± 47.4 μg/mL, and 6.5 ± 0.5 μM Fe2+/mg pinene for the DPPH, ABTS, and FRAP assays, respectively. 120 Furthermore, other major components in the Z. plicatum rhizome EO, such as α-pinene, limonene, germacrene D, bicyclogermacrene, and δ-elemene, along with other minor components, may play a synergistic role in antioxidant activity.
Antimicrobial Effect
Recent studies have shown the antimicrobial effect of the EOs extracted from different parts of several Zingiber species, such as Z. rubens, Z. densissimum, Z. castaneum, Z. cornubracteatum, Z. nitens, Z. nudicarpum, Z. ottensii, Z. recurvatum, Z. vuquangense, Z. magang, Z. tamii, etc.
The EOs (1000 mg/mL) extracted from Z. rubens rhizomes grown in Lamphun, Thailand, could weakly inhibit the growth of Lactobacillus casei (TISTR 390) and Streptococcus mutans (ATCC 25175) with zone of inhibition (ZI) values of 8.83 ± 0.29 mm and 8.17 ± 0.29 mm, respectively. However, the EOs’ inhibition zones were smaller than that of the positive control, chlorhexidine (ZI = 27.67 ± 0.58 mm for L. casei and ZI = 36.0 mm for S. mutans) at a concentration of 2.0 mg/mL. Moreover, this EO also shows the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 250 mg/mL. In comparison, the positive control had an effective antibacterial activity for L. casei (MIC and MBC of 1.0 mg/mL) and S. mutans (MIC and MBC of 0.0039 mg/mL) (p < 0.05). This result shows that the EO has a very weak antibacterial effect compared to chlorhexidine for the anti-cariogenic effect. 44
Huong et al 19 indicated that the EOs isolated from the pseudo-stem of Z. castaneum collected from Nghe An, Vietnam, showed a stronger inhibitory effect on Pseudomonas aeruginosa (ATCC 27853), Aspergillus niger (ATCC 9763), and Fusarium oxysporum (ATCC 48112) with MIC values of 12.5 ± 0.57, 50 ± 1.0, and 50 ± 0.50 µg/mL, respectively. The results showed that the antibacterial effect of the EO was weaker than that of streptomycin (MIC = 0.56-1.8 μg/mL). Notably, this EO did not inhibit the growth of Escherichia coli (ATCC 25922), Bacillus subtilis (ATCC 11774), Staphylococcus aureus subsp. aureus (ATCC 11632), Candida albicans (ATCC 10231), and Saccharomyces cerevisiae (ATCC 16404). 19 In another study, the EOs of leaves and rhizomes of Z. castaneum and Z. nitens from Nghe An, Vietnam, were also evaluated for antimicrobial activity against eight bacterial pathogens, including E. coli, P. aeruginosa, B. subtilis, S. aureus subsp. aureus, A. niger, F. oxysporum, C. albicans, and S. cerevisiae. The leaves and rhizomes EOs of these species displayed antibacterial activity against P. aeruginosa, both with MIC values of 50.0 ± 0.12 μg/mL. Notably, these EOs showed no activity against the other tested microorganisms. 20
In a study by Huong et al, 27 the EOs of Z. tamii leaf and rhizome displayed anti-microbial activity towards Enterococcus faecalis (ATCC 299212) (MIC = 20.25 μg/mL and IC50 = 64.0 μg/mL for leaves, MIC = 20.33 μg/mL and IC50 = 64.0 μg/mL for rhizomes), S. aureus (ATCC 25923) (MIC = 28.56 μg/mL and IC50 = 64.0 μg/mL for leaves, MIC = 56.78 μg/mL and IC50 = 128.0 μg/mL for rhizomes), E. coli (MIC = 44.38 μg/mL and IC50 = 128.0 μg/mL for leaves, MIC = 87.78 μg/mL and IC50 = 256.0 μg/mL for rhizomes), and C. albicans (MIC = 45.62 μg/mL and IC50 = 128.0 μg/mL for leaves, MIC = 89.97 μg/mL and IC50 = 256.0 μg/mL for rhizomes). However, the leaf and rhizome EOs from Z. tamii did not exhibit antimicrobial action against B. cereus (ATCC 14579), P. aeruginosa, and S. enterica (ATCC 1307). Also in this report, the leaf and rhizome EOs of Z. magang exhibited antimicrobial activity towards B. cereus (ATCC 14579) (MIC = 69.67 μg/mL and IC50 = 256.0 μg/mL for leaves, MIC = 78.99 μg/mL and IC50 = 256.0 μg/mL for rhizomes), E. faecalis (MIC = 18.90 μg/mL and IC50 = 64.0 μg/mL for leaves, MIC = 9.99 μg/mL and IC50 = 32.0 μg/mL for rhizomes), and S. aureus (MIC = 45.67 μg/mL and IC50 = 128.0 μg/mL for leaves, MIC = 9.67 μg/mL and IC50 = 32.0 μg/mL for rhizomes). 27 Similarly, the leaf and rhizome EOs from Z. magang did not exhibit antimicrobial action against E. coli (except the leaf oil with MIC and IC50 values of 100.34 and 156.0 μg/mL, respectively), P. aeruginosa, S. enterica, and C. albicans. The positive controls used in this study were streptomycin (MIC = 0.5-1.6 μg/mL), cycloheximide (MIC = 1.2-3.7 μg/mL), and nystatin (MIC = 2.8-4.3 μg/mL). 27
Nguyen-Ngoc et al demonstrated that rhizome EOs of Z. densissimum growing in Vietnam showed good antifungal activity against C. albicans (MIC = 2 µg/mL), which was considerably lower than that of cycloheximide (MIC = 32 µg/mL). Moreover, this rhizome oil also showed significant antibacterial activity against six bacterial strains, with MIC values of 8.0 µg/mL for E. faecalis, S. aureus, and E. coli, while MIC values of 16 and 32 µg/mL for B. cereus and S. enterica, respectively. Noticeably, the EO indicated weak activity against the growth of P. aeruginosa (MIC = 128 µg/mL). Streptomycin was used as a positive control, with MIC values ranging from 32 to 256 µg/mL. 22
In the work of Huong and colleagues, 28 in parallel with the mosquito larvicidal activity, the antimicrobial activity of different parts from Zingiber plants, namely Z. cornubracteatum, Z. nudicarpum, Z. ottensii, Z. recurvatum, and Z. vuquangense, have been investigated, with various results depending on the microbial pathogens used as targets, including Gram-positive bacteria (E. faecalis, S. aureus, B. cereus), Gram-negative bacteria (E. coli, P. aeruginosa, S. enterica), and yeast (C. albicans). Briefly, Huong et al 28 observed weak antimicrobial activity (MIC = 256 μg/mL) of Z. cornubracteatum rhizome oil (Ben En (BE)) against E. coli (IC50 = 68.99 μg/mL) and C. albicans (IC50 = 99.34 μg/mL), Z. cornubracteatum rhizome oil (Pu Mat) against P. aeruginosa (IC50 = 100.34 μg/mL), Z. recurvatum rhizome oil against P. aeruginosa (IC50 = 108.99 μg/mL), and S. enterica (IC50 = 112.67 μg/mL). Notably, Z. nudicarpum rhizome EO (Pu Hoat) exhibited strong antimicrobial activity against E. faecalis (MIC = 2.0 μg/mL, IC50 = 1.33 μg/mL), S. aureus (MIC = 8.0 μg/mL, IC50 = 4.35 μg/mL), B. cereus (MIC = 1.0 μg/mL, IC50 = 0.567 μg/mL), E. coli (MIC = 64 μg/mL, IC50 = 33.22 μg/mL), P. aeruginosa (MIC = 16 μg/mL, IC50 = 8.66 μg/mL), C. albicans (MIC = 16 μg/mL, IC50 = 8.99 μg/mL), and no activity against S. enterica. However, all tested EO samples (except Z. recurvatum rhizome oil) were inactive against S. enterica. Additionally, the EOs from Z. cornubracteatum leaf, rhizome, stem (BE), and leaf (Pu Hoat (PH)), Z. ottensii rhizome, Z. recurvatum leaf, and Z. vuquangense leaf have no activity against P. aeruginosa. Also, E. coli is not affected by the EOs of Z. nudicarpum leaf (PH), Z. ottensii leaf and rhizome, Z. recurvatum leaf and rhizome, and Z. vuquangense leaf. The authors also demonstrated that the EOs of Z. cornubracteatum (BE and PH), Z. nudicarpum, Z. ottensii, Z. recurvatum, and Z. vuquangense showed good antibacterial and antifungal activities against strains, including E. faecalis, S. aureus, and C. albicans, with MIC values of 8.0-128 μg/mL and IC50 values of 8.54-99.34 μg/mL. 28 Compared with the tested EO samples, antibiotics (streptomycin) and antifungals (nystatin and cycloheximide) were used as positive controls with MIC values of 32-256 μg/mL, 8.0 μg/mL, and 32 μg/mL, respectively. 28
In 2023, Huong et al 23 proved that the rhizome EOs of Z. eberhardtii (Lam Dong, Vietnam) and Z. skornickovae (Quang Ngai, Vietnam) were resistant to two bacterial pathogens, including B. subtilis and S. aureus, with the same MIC value of 128 µg/mL. Furthermore, Z. eberhardtii EO also had moderate activity against P. aeruginosa, A. niger, and S. cerevisiae. Both oils were inactive against E. coli, A. brasiliensis, F. oxysporum, and C. albicans (MIC > 256 µg/mL). 23 In contrast, Z. eberhardtii rhizome oil exhibited weak activity against C. sporogenes (MIC = 256 µg/mL), while Z. skornickovae oil had no activity (MIC > 256 µg/mL). Noticeably, Z. skornickovae rhizome oil exhibited better antibacterial activity against S. cerevisiae (MIC = 64 µg/mL) than Z. eberhardtii oil (MIC = 128 µg/mL) but was weaker than nystatin (MIC = 8 µg/mL). Regarding antibacterial activity, the EO samples were much weaker than streptomycin (MIC = 4.0-8.0 µg/mL). 23
Notably, the main components of Zingiber EOs, such as Z. nitens (β-pinene), Z. vuquangense (β-pinene, β-caryophyllene), Z. castaneum (bicyclogermacrene, sabinene, camphene), Z. cornubracteatum (bicyclogermacrene, β-pinene, β-caryophyllene, linalool, (E)-nerolidol), Z. ottensii (zerumbone, β-caryophyllene, sabinene, terpinen-4-ol), Z. recurvatum (β-pinene, β-caryophyllene), Z. atroporphyreum (β-pinene), Z. densissimum (β-pinene, α-pinene, β-phellandrene), Z. eberhardtii (linalool, 1,8-cineole), Z. skornickovae (β-pinene, β-caryophyllene), Z. magang (β-pinene, (E)-nerolidol), Z. tamii (β-pinene, sabinene), Z. rubens (Z-citral, zerumbone), and Z. nudicarpum (bicyclogermacrene, β-pinene, 1,8-cineole, β-caryophyllene, humulane-1,6-dien-3-ol) contributed to the antimicrobial properties of each Zingiber EOs. For example, previous studies have demonstrated that β-pinene and α-pinene have antimicrobial activity against some pathogenic microorganisms, such as C. albicans, Cryptococcus neoformans, Rhizopus oryzae, and methicillin-resistant S. aureus, with MIC values ranging from 117 to 4150 µg/mL. 121 Furthermore, β-pinene was also shown to have antibacterial activity against S. aureus, S. epidermidis, S. pyogenes, and S. pneumoniae with MIC values of 20 µL/mL, while the MIC values of α-pinene against these microorganisms ranged from 5.0 to 20 µL/mL. 122 Terpinen-4-ol exhibited antibacterial activity against ten S. aureus strains with MIC and MBC values of 0.25% and 0.5% (v/v), respectively. 123 Also, the antibacterial activity of terpinen-4-ol against oral pathogens, namely S. mutans and Lactobacillus acidophilus, with effective inhibitory concentrations of 0.24% and 0.95% (v/v), respectively. 124 β-caryophyllene has been shown to significantly reduce the level of infection by Helicobacter pylori at both concentrations of 100 and 500 μg/g. 125 β-Caryophyllene also exhibited strong antibacterial activity against B. cereus, B. subtilis, S. aureus, E. coli, Klebsiella pneumoniae, P. aeruginosa, Aspergillus niger, Penicillium citrinum, R. oryzae, and Trichoderma reesei, with MIC values ranging from 3.0 ± 0.4 to 14.0 ± 2.7 μM. 126 The antibacterial and antifungal activities of 1% zerumbone were recorded against S. aureus, P. aeruginosa, E. coli, and C. albicans, with the percentages of inhibition being 88.17 ± 0.01%, 84.90 ± 0.01%, 68.21 ± 0.03%, and 86.02 ± 0.02%, respectively. 127 (E)-nerolidol has been reported to possess antibacterial activities against B. cereus, Citrobacter diversus, E. coli, P. aeruginosa, P. fluorescens, Salmonella abony, S. aureus, and S. epidermidis with MIC and MBC values from 0.1 to 0.4 and 0.2 to 0.4 µM, respectively. 128 Linalool has been shown to have antimicrobial activities against various microorganisms, such as S. aureus, E. coli, K. pneumoniae, P. mirabilis, P. aeruginosa, C. albicans, C. glabrata, and C. krusei, with MIC values from 12.5 to 100 mM. 129 In another study, linalool showed potential antifungal activity toward strains of fungi, including Candida spp., Cryptococcus spp., Geotrichum spp., and Saccharomyces spp., with MIC values in the range of 0.5-8.0 mg/mL. 130
Despite the effectiveness against varied microorganisms of several constituents separated from Zingiber EO, the mechanism of the antimicrobial properties of EO has not been fully reported.
Larvicidal Effect
Several previous studies report that EOs extracted from various plants, particularly Zingiber oils, have larvicidal and pupicidal effects against mosquitoes.
For the larvicidal effect, Z. mekongense whole plant EO exhibited significant toxic effects against Aedes albopictus mosquitoes. At concentrations of 5.0% and 10.0%, Z. mekongense oil showed a 50% lethal time (LT50) of 0.36 h and 0.25 h, respectively with a 50% lethal concentration (LC50) of 3.0%, while this EO did not induce any mortality against Ae. albopictus larvae at concentrations of 1.0%. Therefore, The highest activity with 100% mortality against the adults of Ae. albopictus was recorded to 10.0% of Z. mekongense oil with LT50 of <0.25 h and LC50 of 3.0%. 117 The results of this report prove that this EO had a significant larvicidal activity against Ae. albopictus mosquitoes.
Huong et al 20 demonstrated that the rhizome and leaf oils of Z. castaneum collected from Pu Hoat Nature Reserve, Nghe An, Vietnam, had larvicidal activity against Ae. aegypti and Culex quinquefasciatus. Accordingly, the leaf and rhizome oils of Z. castaneum (at 24 h and 48 h) exhibited 100% mortality against Ae. aegypti at concentrations of 100 μg/mL and 200 μg/mL, respectively. 20 Notably, the leaf and rhizome oils exhibited larvicidal activity against Ae. aegypti with LC50 values of 39.30 and 121.43 μg/mL, respectively (at 24 h), and LC90 values of 89.94 and 145.28 μg/mL, respectively (at 24 h). Moreover, the leaf and rhizome oils exhibited a larval mortality of 100% against Cx. quinquefasciatus at a concentration of 150 μg/mL with LC50 values of 84.97 and 88.86 μg/mL, respectively, and LC90 values of 141.45 and 117.68 μg/mL, respectively (at 24 h). 20 In this study, the leaf and rhizome oils of Z. nitens from Pu Hoat Nature Reserve, Nghe An, Vietnam have been reported to exhibit mosquito larvicidal activity. Brifly, the leaf and rhizome oils possessed a mortality of 100% against Ae. aegypti at concentrations of 50 μg/mL and 100 μg/mL, respectively; however, at a concentration of 100 μg/mL, only the rhizome oil displayed a mortality of 92.5% against Cx. quinquefasciatus. Furthermore, the leaf and rhizome oils showed larvicidal activity against Ae. aegypti with LC50 values of 17.58 and 29.60 μg/mL after 24 h, while the LC90 values were 23.25 and 37.60 μg/mL, respectively, for the same mosquito. Similarly, the rhizome oil showed larvicidal activity against Cx. quinquefasciatus with LC50 values of 64.18 and 59.06 μg/mL (after 24 h and 48 h) and LC90 values of 92.68 and 84.31 μg/mL during the same time. 20 A previous report demonstrated that rhizome EO of Z. castaneum from Pu Hoat Nature Reserve, Nghệ An Province, Vietnam exhibited good mortality (100%) against Ae. albopictus at a concentration of 100 µg/mL at 24 h and 48 h. 118 Moreover, this oil also showed significant larvicidal activity against Ae. albopictus, with LC50 values of 49.85 μg/mL (at 24 h) and 43.93 μg/mL (at 48 h), as well as LC90 values of 71.71 μg/mL (at 24 h) and 68.12 μg/mL (at 48 h). 118 The evidence of these reports proved that EOs hydro-distilled from the Z. castaneum oils processed good mortality and larvicidal effects on Ae. albopictus, Ae. aegypti, and Cx. quinquefasciatus.
In 2020, Huong and colleagues 28 demonstrated that the rhizome of Z. ottensii collected from Vietnam possessed larvicidal activity against Ae. aegypti (LC50 = 38.16 μg/mL, LC90 = 57.87 μg/mL at 24 h), Ae. albopictus (LC50 = 19.79 μg/mL, LC90 = 30.81 μg/mL at 24 h), and Cx. quinquefasciatus (LC50 = 27.19 μg/mL, LC90 = 40.09 μg/mL at 24 h). Moreover, the rhizome EO of Z. recurvatum grown in Vietnam had larvicidal activity against Ae. aegypti (LC50 = 20.90 μg/mL, LC90 = 36.35 μg/mL at 24 h), Ae. albopictus (LC50 = 45.58 μg/mL, LC90 = 58.58 μg/mL at 24 h), and Cx. quinquefasciatus (LC50 = 31.67 μg/mL, LC90 = 47.02 μg/mL at 24 h). Similarly, the Z. neotruncatum rhizome EO grown in Vietnam had larvicidal activity against Ae. aegypti (LC50 = 34.95 μg/mL, LC90 = 51.49 μg/mL at 24 h), Ae. albopictus (LC50 = 21.50 μg/mL, LC90 = 31.99 μg/mL at 24 h), and Cx. quinquefasciatus (LC50 = 33.58 μg/mL, LC90 = 42.76 μg/mL at 24 h). Furthermore, the EO from Z. cornubracteatum rhizome also presented larvicidal activity against Ae. aegypti (LC50 = 16.97 μg/mL, LC90 = 24.56 μg/mL at 24 h), Ae. albopictus (LC50 = 12.72 μg/mL, LC90 = 21.56 μg/mL at 24 h), and Cx. quinquefasciatus (LC50 = 24.31 μg/mL, LC90 = 41.34 μg/mL at 24 h). Comparing the mosquito larvicidal effects of these four rhizome EOs showed that Z. cornubracteatum, Z. ottensii, and Z. neotruncatum EOs had a stronger mosquito larvicidal effect on Ae. albopictus and Cx. quinquefasciatus than Z. recurvatum EO; conversely, Z. recurvatum EO had a stronger mosquito larvicidal effect than Z. ottensii and Z. neotruncatum EOs on Ae. aegypti. Additionally, the EO from the rhizome of Z. cornubrceatum showed the strongest larvicidal activity against Ae. aegypti compared to the above three Zingiber species. However, these EOs had a much weaker mosquito larvicidal effect than the positive control (permethrin, LC50 = 0.0024-0.0188 μg/mL). 28
The leaf EO of Z. nudicarpum from Pu Hoat (Vietnam) showed larvicidal activity against Ae. aegypti with an LC50 value of 19.30 μg/mL and an LC90 value of 23.74 μg/mL after 24 h, while the LC50 and LC90 values were 23.44 μg/mL and 31.81 μg/mL, respectively, for the rhizome EO towards the same mosquito. For Ae. albopictus, this leaf EO exhibited larvicidal activity with an LC50 value of 22.33 μg/mL and an LC90 value of 31.12 μg/mL after 24 h. In contrast, the LC50 and LC90 values of the rhizome EO were 28.05 μg/mL and 42.09 μg/mL, respectively. Similarly, the leaf and rhizome EOs also presented larvicidal activity against Cx. quinquefasciatus (LC50 = 12.44 μg/mL, LC90 = 44.29 μg/mL at 24 h and LC50 = 11.50 μg/mL, LC90 = 27.15 μg/mL, respectively, at the same period). 28 Briefly, the leaf EO of Z. nudicarpum, indicated the best larvicidal activity against Ae. aegypti and Ae. albopictus when compared with the rhizome oil. Notably, the leaf and rhizome EOs from Z. nudicarpum were significantly active against Cx. quinquefasciatus larvae, with LC50 values of 12.44 and 11.50 μg/mL, respectively. 28
Huong et al 11 demonstrated that the EO isolated from the rhizome of Z. collinsii exhibited the highest mortality rate (100%) for Ae. albopictus at 24 h (100 μg/mL) and 48 h (50 and 100 μg/mL) exposure times, while the highest mortality rate (100%) was observed at 100 μg/mL for Cx. quinquefasciatus at 24 h and 48 h. In this study, Huong et al 11 also showed that this EO had significant larvicidal effects on Ae. albopictus (LC50 values of 25.51 μg/mL (at 24 h) and 20.03 μg/mL (at 48 h); LC90 values of 40.22 μg/mL (at 24 h) and 24.51 μg/mL (at 48 h)) and Cx. quinquefasciatus (LC50 values of 50.11 μg/mL (at 24 h) and 36.18 μg/mL (at 48 h); LC90 values of 71.53 μg/mL (at 24 h) and 55.11 μg/mL (at 48 h)). 11 The results obtained in this report showed that the EO of Z. collinsii rhizome had promising effects on larvicidal activities against Ae. albopictus and Cx. quinquefasciatus.
Additionally, the studies identified the main phytoconstituents, namely β-pinene, bicyclogermacrene, β-caryophyllene, α-humulene, 1,8-cineole, α-terpineol, terpinen-4-ol, sabinene, (E)-nerolidol, etc in some Zingiber oils (eg, Z. recurvatum, Z. nudicarpum, Z. collinsii, Z. cornubracteatum, Z. castaneum, etc), which are bioactive components that play essential roles in mosquito control, as reported in previous studies.131–137
Figure 7 presents the larvicidal activity of EOs from different parts of several Zingiber species.
The graph obtained from a comparative analysis of the larvicidal activity of Zingiber EOs against Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus.
The mosquito larvicidal activity of EOs was evaluated as strong (LC50 ≤ 50 µg/mL), moderate (LC50 ≤ 100 µg/mL), weak (LC50 ≤ 750 µg/mL), and inactive (LC50 > 750 µg/mL) activities, as previously reported.28,138 Figure 7 shows a comparative analysis of the larvicidal activity against Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus of the EOs of the investigated Zingiber species, which revealed some interesting observations. A total of nine Zingiber EOs (Z. cornubracteatum rhizome > Z. nitens leaf > Z. nudicarpum leaf > Z. recurvatum rhizome > Z. nudicarpum rhizome > Z. nitens rhizome > Z. neotruncatum rhizome > Z. ottensii rhizome > Z. castaneum leaf) showed strong larvicidal activity against Ae. aegypti mosquitoes with LC50 values from 16.97 to 39.3 μg/mL, while Z. castaneum rhizome EO exhibited moderate larvicidal activity (LC50 = 121.43 μg/mL). For Ae. albopictus, eight Zingiber EOs (Z. cornubracteatum rhizome > Z. ottensii rhizome > Z. neotruncatum rhizome > Z. nudicarpum leaf > Z. collinsii rhizome > Z. nudicarpum rhizome > Z. recurvatum rhizome > Z. castaneum rhizome) indicated vigorous larvicidal activity with LC50 values from 12.72 to 49.85 μg/mL. Furthermore, six Zingiber EOs (LC50 = 11.5-33.58 μg/mL, Z. nudicarpum rhizome > Z. nudicarpum leaf > Z. cornubracteatum rhizome > Z. ottensii rhizome > Z. recurvatum rhizome > Z. neotruncatum rhizome) and three Zingiber EOs (LC50 = 64.18-88.86 μg/mL, Z. nitens rhizome > Z. castaneum leaf > Z. castaneum rhizome) exhibited vigorous and moderate Cx. quinquefasciatus larvicidal activities, respectively. Therefore, the EOs from different parts of eight Zingiber species successfully controlled the larvae of Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus with LC50 values from 11.5 to 121.43 µg/mL. Generally, the present discoveries underscore the versatile uses of Zingiber EOs in the application of mosquito larvicidal treatments.
These results suggest that EOs from Zingiber species may be safe and eco-friendly alternatives, providing a novel source of natural products for mosquito control.
Antidiabetic Effect
The antidiabetic activity of the EO of Z. atroporphyreus collected from Phu Tho, Vietnam, was determined for their ability to inhibit α-amylase and α-glucosidase. 17 The EOs obtained from the leaves and rhizomes of Z. atroporphyreus showed weak α-amylase inhibiting activities, with IC50 values of 0.39 ± 0.03 and 0.30 ± 0.03 mg/mL, respectively, while the positive control (acarbose) showed α-amylase inhibition with an IC50 value of 0.09 ± 0.00 mg/mL. Therefore, both tested EOs had weaker anti-α-amylase activity than acarbose. Notably, the EOs of leaves and rhizomes of Z. atroporphyreus showed no inhibition of α-glucosidase as reported by Tran-Trung et al. 17
Anticancer Effect
The anticancer activity of the EOs from Z. ottensii rhizome (Thailand) was assessed against four human cancer cells (ie, the non-small cell lung cancer (A549), breast cancer (MCF-7), cervical cancer (HeLa), and chronic myelogenous leukemia (K562)) using an MTT assay. 36 The results showed that the rhizome oil possessed cytotoxic activity against A549, MCF-7, HeLa, and K562 cell lines with IC50 values of 43.37 ± 6.69, 9.77 ± 1.61, 23.25 ± 7.73, and 60.49 ± 9.41 μg/mL, respectively. Compared with the anticancer drugs used as the positive control, this rhizome oil showed a higher effective anticancer effect than cyclophosphamide against all tested cells (IC50 > 400 μg/mL) and cytarabine against A549 (IC50 > 100 μg/mL) and K562 (IC50 > 100 μg/mL); on the contrary, this EO is very weaker than doxorubicin (IC50 = 0.016-0.80 μg/mL) and idarubicin (IC50 = 0.004-0.41 μg/mL). Briefly, Z. ottensii rhizome oil indicated the highest cytotoxicity against MCF-7 (IC50 = 9.77 ± 1.61 μg/mL). 36 The apoptosis effect of Z. ottensii rhizome EO was also evaluated against MCF-7 cells at concentrations of 2.0, 3.0, and 10 μg/mL that showed at the sub-G1 phase of cell cycle analysis. 36 This EO at concentrations of 2.0, 3.0, and 10 μg/mL showed the % apoptotic cells with values of 9.50 ± 4.12%, 10.07 ± 4.59%, and 26.50 ± 6.52%, respectively, compared with cytarabine (2.0 μg/mL) of 53.73 ± 1.63% apoptotic cells. These results showed that the EO tended to increase cell apoptosis dose-dependently. Notably, the EO (10 μg/mL) significantly increased the ratio of apoptotic cells with a value of 26.50 ± 6.52% (p < 0.05) compared to cell control (9.80 ± 1.35%) and vehicle control (10.30 ± 1.05%). 36
Modern nanoformulations containing Zingiber EO: Recent evidence has reported that nanoformulations containing Z. ottensii rhizome EO (ZOEO) showed cytotoxic activity against various tested cancer cells (A549, MCF-7, HeLa, and K562). 36 The nanogel mixture containing ZOEO composed of NE-ZO (25% Tween 80 + 10% of ZOEO, water), ME-ZO (30% Tween 80, ethyl alcohol (2:1) + 10% of ZOEO), NG-ZO (under 2% of a gelling agent (nanoemulgels or microemulgels) + NE-ZO), and MG-ZO (under 2% of a gelling agent (nanoemulgels or microemulgels) + ME-ZO) were prepared to obtain four types of oil-in-water nanoformulations. As a result, the oil-in-water nanoformulations exhibited significantly stronger cytotoxicity than ZOEO alone (IC50 = 43.37 ± 6.69 μg/mL for A549 cells, IC50 = 9.77 ± 1.61 μg/mL for MCF-7 cells, IC50 = 23.25 ± 7.73 μg/mL for HeLa cells, IC50 = 60.49 ± 9.41 μg/mL for K562 cells). Specially, NE-ZO (IC50 = 18.45 ± 3.33 ng/mL for A549 cells, IC50 = 1.08 ± 2.58 ng/mL for MCF-7 cells, IC50 = 5.81 ± 2.38 ng/mL for HeLa cells, IC50 = 32.48 ± 1.21 ng/mL for K562 cells) and ME-ZO (IC50 = 28.24 ± 12.51 ng/mL for A549 cells, IC50 = 0.74 ± 0.45 ng/mL for MCF-7 cells, IC50 = 7.24 ± 2.493 ng/mL for HeLa cells, IC50 = 33.31 ± 2.37 ng/mL for K562 cells) demonstrated stronger anticancer activity than NG-ZO (IC50 = 33.76 ± 8.26 ng/mL for A549 cells, IC50 = 4.31 ± 0.91 ng/mL for MCF-7 cells, IC50 = 8.88 ± 1.97 ng/mL for HeLa cells, IC50 = 35.35 ± 1.72 ng/mL for K562 cells) and MG-ZO (IC50 = 6.45 ± 5.84 ng/mL for A549 cells, IC50 = 11.01 ± 2.54 ng/mL for MCF-7 cells, IC50 = 23.25 ± 7.73 ng/mL for HeLa cells, IC50 = 36.23 ± 2.48 ng/mL for K562 cells), respectively. 36 The study suggested that NE-ZO and ME-ZO had higher anticancer activity than NG-ZO and MG-ZO due to the retardation effect of ZOEO release by the gel matrix. The study provided scientific evidence that nano-formulations were significantly effective in delivering ZOEO to cancer cells, suggesting that developing nano-formulations of modern from this EO holds great promise for the pharmaceutical field.
In another study, Ruttanapattanakul et al 119 also reported that the rhizome EO of this species showed apoptosis activity against early Hela human cervical cancer cells with approximately 10%-20% treated with 1:6000 and 1:3000 dilutions of EO, respectively. Finally, this EO at the 1:6000 and 1:3000 dilutions significantly contributed to approximately 15% and 35% apoptotic death in HeLa cells, respectively. Using Western blot analysis, Ruttanapattanakul et al 119 have recently demonstrated that HeLa cells treated with EO significantly reduced pro-caspase 9, pro-caspase 3, and full-length PARP protein. In contrast, the elevation of active caspase-9, caspase-3, and cleaved PARP protein was increased. These results identified Z. ottensii rhizome EO-induced HeLa cell death via apoptosis signaling. Moreover, Z. ottensii EO (at dilutions of 1:50 000 and 1:25 000) reduced IL-6 levels (approximately 120 and 90 pg/mL, respectively) in the culture supernatants of the cancer cells, which is one of the specific cytokines responsible for cervical cancer development and progression in HeLa cells. Interestingly, immunofluorescence studies and Western blot analyses showed that Z. ottensii EO (at 1:3000 and 1:6000 dilutions for 24 h) suppressed epidermal growth factor (EGF)-induced pAkt and pERK1/2 signaling pathway activation, as well as reduced the proliferation and survival signaling of HeLa cervical cancer cells. This research offers strong evidence that Z. ottensii rhizome EO inhibits the proliferation and survival of cervical cancer cells, suggesting that it might be a good option for developing an anti-cancer agent for treating certain cervical cancers. 119
It is demostrated that zerumbone,139–141 sabinene, 142 terpinen-4-ol,143,144 α-humulene,145,146 β-pinene,132,147 and 1,8-cineole,148,149 as the main components of all tested Z. ottensii rhizome EOs from Thailand, may play an important role in the recorded anti-cancer activities mediated by suppression of proliferation, induction of cell cycle arrest, and apoptosis in various cancers.
Cytotoxicity
The cytotoxicity assay is one of the criteria for evaluating the safety profiling of bioactive phytocompounds.150,151 In a study by Pukumpuang and Chaliewchalad, 44 the rhizome EO from Z. rubens showed non-toxicity to cells in vitro with a 50% cytotoxic concentration (CC50) or half maximal inhibitory concentration (IC50) of 2.5 μg/mL, while ethanolic extracts from different parts of Z. rubens (CC50 = 30.32-377.35 μg/mL) were more cytotoxic than the aqueous extract (CC50 > 1000 μg/mL) to the Vero cell. 44 According to the US National Cancer Institute, the criteria of cytotoxic activity for crude plant extract is CC50/IC50 < 20 µg/mL or 10 µM upon 48 h or 72 h incubation.152,153 Therefore, plant extracts and EOs of Z. rubens are not cytotoxic against normal mammalian cells.
Previously reported data on the cytotoxic activity of Z. ottensii rhizome oil through brine shrimp lethal assay showed that this oil exhibited moderate cytotoxic activity with LC50 values of 65.5 µg/mL. 34 In addition to determining the acute oral toxicity in rats, Z. ottensii rhizome oil's teratogenic and embryotoxic effects were assessed in zebrafish embryos and larvae via a study by Thitinarongwate et al 37 Embryotoxicity was evaluated at five different concentrations of Z. ottensii EO, i.z., 3.91, 1.95, 0.98, 0.49, and 0.24 µg/mL. The results indicated that the toxic activity of EOs appeared to be concentration-dependent. In zebrafish embryos, no mortality was induced by the lowest EO content at 0.24 µg/mL. In contrast, a significantly increased mortality rate was recorded in zebrafish embryos exposed to Z. ottensii EO at a concentration of 0.49-3.91 µg/mL (p < .05). 37 The groups treated with EO (at concentrations of 1.95 and 3.91 µg/mL) showed no signs of viable zebrafish embryos, with an LC50 value of 1.003 µg/mL. In zebrafish embryos, morphological abnormalities, decreased hatchability, and reduced heart rate were also records of teratogenicity for this rhizome oil. In the female Sprague Dawley rat (Rattus norvegicus) model, Z. ottensii rhizome EO (2000 mg/kg, p.o.) resulted in no mortality within 14 days of testing, and behavioral manifestations (eg, sedation, lethargy, and ataxia) were noted but recovered later to normal, indicating insignificant toxicities. 37 These findings suggest that Z. ottensii rhizome EO has embryotoxic and teratogenic effects in zebrafish embryos but does not cause lethality or acute oral toxicity in tested rats. Further chronic toxicity studies are needed to evaluate the safety of products developed from Z. ottensii rhizome EO.
In conclusion, the presence of several bioactive components from EOs may be synergistically or individually responsible for the various pharmacological properties of each Zingiber species. Among these, β-pinene, α-pinene, β-caryophyllene, β-elemene, bicyclogermacrene, sabinene, camphene, linalool, (E)-nerolidol, terpinen-4-ol, 1,8-cineole, humulane-1,6-dien-3-ol, β-phellandrene, and zerumbone are representative ingredients that mainly possess antioxidant, antimicrobial, anti-larvicidal, anticancer activities, and so on. Based on the literature survey of 23 Zingiber species in this work, the current results have recorded several Zingiber species related to antioxidant (Z. plicatum), antimicrobial (Z. rubens, Z. castaneum, Z. nitens, Z. tamii, Z. magang, Z. densissimum, Z. cornubracteatum, Z. nudicarpum, Z. ottensii, Z. recurvatum, Z. vuquangense, Z. eberhardtii, and Z. skornickovae), anti-larvicidal (Z. castaneum, Z. mekongense, Z. nitens, Z. ottensii, Z. neotruncatum, Z. cornubracteatum, Z. nudicarpum, Z. collinsii, and Z. recurvatum), antidiabetic (Z. atroporphyreus), anticancer (Z. ottensii), and cytotoxic (Z. rubens and Z. ottensii) effects (Figure 8). However, some Zingiber species, including Z. gramineum, Z. rufopilosum, Z. monophyllum, Z. pellitum, and Z. acuminatum, have not been recorded for pharmacological effects so far. It is suggested that these Zingiber species are valuable and important plant sources contributing to the development of natural medicines. In addition to their therapeutic applications, EOs from Zingiber plants and their components become potential sources of raw materials as natural preservatives for foods.
Biological activities of several Zingiber species.
Limitations of the Evidence and Future Perspectives
Recently, the various pharmacological effects of the EOs from different parts of some Zingiber species have been studied in vitro and in vivo. Among the studied bioactive effects, including antimicrobial, antioxidant, antidiabetic, anticancer, larvicidal, and cytotoxic activities of several Zingiber species, have been scientifically proven (Figure 8). However, these modern pharmacological effects have not been fully and systematically studied for some Zingiber species mentioned in the current study. Moreover, some previous studies only stopped at studying the chemical composition of EOs (eg, Z. gramineum, Z. rufopilosum, Z. monophyllum, Z. pellitum, and Z. acuminatum). Therefore, some future prospects are proposed for these 23 Zingiber species.
Firstly, with such limited research information, the medicinal values of EOs from different parts of some Zingiber species (eg, Z. eberhardtii, Z. ottensii, and Z. collinsii) are mainly recorded based on the traditional medicine perspective. Therefore, there is still a significant lack of scientific evidence regarding these plants’ pharmacological, pharmacokinetic, pharmacodynamic, and phytoconstituent information. Hence, further elucidation of the pharmacological effects, molecular mechanisms, and toxicity (eg, acute and chronic toxicity tests) of Zingiber species is needed.
Secondly, the EOs from several Zingiber species can be considered as promising agents for antimicrobial, anti-larvicidal, and anticancer drugs. However, the lack of clinical study information leads to underutilizing its therapeutic potential. This gap can be filled through directions for future research.
Thirdly, further exploration should be conducted to explore the unknown components of Zingiber species. Moreover, the different extraction methods related to the EO yield (eg, hydrodistillation, steam distillation, microwave-assisted hydrodistillation, etc) and isolation procedures for the effective bioactive compounds of Zingiber species should be investigated.
Finally, some Zingiber species can be found in many countries, such as China, Vietnam, Laos, Cambodia, Thailand, etc (Figure 1) and are distributed in many different climates and soil conditions. Therefore, environmental factors, geographic location or cultivation area, harvest time or season, stress during growth, maturity, drying, and storage need further study because they may affect the content and chemical composition of EOs. Additional investigation into the preservation, farming, and advancement of Zingiber species is required to supply more novel raw materials for pharmaceutical and commercial applications. Fingerprinting techniques are also used to better understand the differences between the main bioactive components collected from different regions, thereby providing a basis for quality control of Zingiber species.
This evaluation highlights the significance of Zingiber EOs and provides several recommendations for the future development of Zingiber species.
Conclusion
In conclusion, 23 Zingiber species have been comprehensively overviewed for the first time, thereby contributing to understanding the dominant chemical compositions and biological activities of Zingiber EOs in nature. The literature reports indicated that EOs from 23 Zingiber species have various pharmacological activities, such as antioxidant, antimicrobial, larvicidal, antidiabetic, anticancer, and cytotoxic effects. It can be seen that EOs from Zingiber species are potential sources of natural compounds for development in the food, cosmetic, and pharmaceutical industries.
Footnotes
Abbreviations
Acknowledgment
The authors thank Dr Van Thanh Tien Nguyen (Industrial University of Ho Chi Minh City, Vietnam) for his comments and corrections to this overview.
Authors’ Contributions
TVC provided the research idea. TVC and TB performed analysis, wrote, and discussed. TVC and NTTH read and revised the manuscript. All authors read and approved the final manuscript.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Ethical Approval
Ethical approval is not applicable for this review article.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Statement of Human and Animal Rights
This review article does not contain any studies with human or animal subjects.
Statement of Informed Consent
There are no human subjects in this review article and informed consent is not applicable.
