Abstract
Meistera tomrey, Zingiberaceae is a species native to Indochina. The present study reports the chemical compositions of essential oils extracted from the pseudostem and leaves of M tomrey. The results of the gas chromatography-mass spectrometry (GC/MS) analysis revealed varying compositions of specific compounds in both the pseudostem and leaves. In the pseudostem, β-pinene accounted for 14.2% and 1,8-cineole for 13.5%. As for the leaves, β-pinene comprised 6.6% and 1,8-cineole 16.7%. α-Pinene represented 6.9% in the pseudostem and 4.6% in the leaves, while borneol contributed 4.6% in the pseudostem and 4.2% in the leaves. Additionally, (E)-caryophyllene constituted 3.6% in the pseudostem and 4.4% in the leaves, and (E)-nerolidol 3.5% in the pseudostem and 7.6% in the leaves. This is the first report on the chemical compositions of essential oil from M tomrey.
Introduction
In Vietnam, the ginger family is represented by 21 genera and about 100 species. 1 Several reports exist on the chemical compositions of essential oils from Zingiberaceae.2–7 Meistera Giseke, Zingiberaceae, is a genus native to tropical and subtropical Asia to North Queensland. The genus was previously classified as being synonymous with the genus Amomum Roxb.2,8 There are 44 species of Meistera, of which 12 have been recorded in Vietnam. These are M aculeata, M caudata, M celsa, M sudae, M chinensis, M cristatissima, M elephantorum, M gagnepainii, M koenigii, M muricarpa, M tormey, and M vespertilio.1,9 Information is scanty on the chemical characterization and pharmacological evaluation of extracts from Mesitera species. Phytochemical screening showed that M chinensis fruit extracts contained saponins, terpenoids, steroids, alkaloids, phenolics, tannins, and flavonoids. 3 The extracts exhibited antioxidant activity by scavenging DPPH radicals in a dose-dependent pattern with an IC50 of 47.62 ± 2.93. The results of the analysis of variance on antibacterial and antifungal properties showed that there was a significant difference (p = .00 < .05) against fungal and bacterial growth. 3
Meistera tomrey (Gagnep.) Škorničk & M. F. Newman is a rhizomatous geophyte and grows primarily in the wet tropical biome. The native range of this species is Indo-China. 10 It is known in Vietnamese as Sa nhan tomre and is found mainly in Lâm Đông forest reserve. There is no record of the phytochemical composition and biological potential of M. tomrey. Previous research has highlighted the chemical compositions of essential oils from several other Meistera species. For example, β-pinene (27.4%), α-pinene (21.2%), limonene (12.1%), and myrcene (8.6%) were the characteristic components of M sudae leaf essential oil. 4 The leaf essential oil of M caudata contained 27.61% of α-pinene, 21.29% of β-pinene, and 8.62% of camphene while the figures for the rhizome essential oil were 10.37%, 9.69%, and 12.1%, respectively. 5 A recent finding identified β-pinene (30.8%), and α-pinene (23.8%) as the principal compounds of the leaf oil of M caudata, while bicyclogermacrene (13.3%), camphene (10.7%), and 1,8-cineole (7.7%) were significant compounds of the rhizome essential oil. 11 The main compounds of the leaf oil of M cristatissima were α-pinene (19.8%), caryophyllene oxide (9.8%), and (E)-nerolidol (7.3%), whereas spathulenol (14.6%), bornyl acetate (7.4%), caryophyllene oxide (7.1%), cubeban-11-ol (6.5%), and humulene epoxide II (5.3%) were the abundant compounds of the rhizome oil. 12 The leaf oil of M sudae exhibited strong antimicrobial activity, with the same minimum inhibitory concentration (MIC) value of 25 µg/mL against the 2 Gram-positive bacteria, Bacillus subtilis and Staphylococcus aureus, and the yeast Saccharomyces cerevisiae. 4 This good antimicrobial result was attributed to the role of the major components such as α-pinene, β-pinene, and limonene present in the essential oil. 4 The essential oils from M caudata were also shown to exhibit strong antimicrobial activities against several pathogenic bacterial and fungal strains with MIC values ranging from 8 to 128 μg/mL. The essential oil displayed the most potent activity against Enterococcus faecalis with a MIC value of 8 μg/mL. 6 The leaf oil of M caudata possessed a MIC value of 256 µg/mL against 2 Gram-positive bacteria, B subtilis and S aureus, and the yeast Sacharomyces cerevisiae, and a MIC value of 128 µg/mL against the fungus Fusarium oxysporum. Meanwhile, M caudata rhizome oil was moderately active against the fungus Aspergillus niger and yeast S cerevisiae, with a MIC value of 128 µg/mL. This oil also inhibited the Gram-positive bacterium B subtilis and Gram-negative bacterium Escherichia coli with a MIC value of 256 µg/mL. 11 The leaf oil of M cristatissima showed greater antimicrobial activity than the rhizome oil against E faecalis, B subtilis, and C albicans with MIC values of 20.45, 29.45, and 18.45 μg/mL, respectively. 12
In the current study, we report the chemical compositions of the essential oils from the pseudostem and leaves of M tomrey from Vietnam. This is part of ongoing research activities aimed at the determination of chemical constituents and biological actions of essential oils of Zingiberaceae species from Vietnam.6,7,12
Results and Discussion
The yields of the essential oils were 0.33% for the pseudostem and 0.28% for the leaves (Table 1). Overall, 75 different constituents, mostly terpenes, were identified in both essential oils. A total of 60 compounds accounting for 89.3% of the total oil content were identified in the pseudostem essential oil of M tomrey. The essential oil was pale-yellow-colored. The oil was characterized by oxygenated monoterpenes (29.7%), monoterpene hydrocarbons (23.8%), oxygenated sesquiterpenes (21.9%), and sesquiterpene hydrocarbons (10.4%). The compounds occurring in higher quantity were β-pinene (14.2%), 1,8-cineole (13.5%), α-pinene (6.9%), borneol (4.6%), (E)-caryophyllene (3.6%), and (E)-nerolidol (3.5%). There was also a significant amount of linalool (4.1%), α-eudesmol (3.1%), β-eudesmol (2.4%), and guaiol (2.6%), among others.
Chemical Constituents of Essential Oils From the Pseudostem and Leaves of M tomrey.
Abbreviations: RT, retention time; RIs, retention indices.
Elution order on Equity-5 capillary column.
Retention indices on Equity-5 capillary column.
Literature retention index taken from Adams. 14
– Not identified.
The 55 constituents of the leaf essential oil were comprised of oxygenated monoterpenes (34.6%), oxygenated sesquiterpenes (22.8%), monoterpene hydrocarbons (13.2%), and sesquiterpene hydrocarbons (10.3%). The pale-yellow-colored essential oil sample had 5.4% of fatty acids and 1.1% of nonterpene compounds. The total oil content was 87.3%. The main constituents of the essential oil include β-pinene (6.6%), 1,8-cineole (16.7%), α-pinene (4.6%), borneol (4.2%), (E)-caryophyllene (4.4%), and (E)-nerolidol (7.6%). The minor compounds present in the essential oil were linalool (3.8%), myrtenol (3.5%), (2E)-octenol butanoate (2.5%), and butyl butyryl lactate (2.2%).
Of the 76 identified constituents in the 2 oils, 39 were common to both. However, quantitative variations were observed among the main and minor compounds of the essential oils. For example, for the major compounds, the amount of α-pinene was 6.9% and 4.6%, respectively, for both the pseudostem and leaves oil samples. The β-pinene contents were 14.2% and 6.6%, respectively, while 13.5% and 16.7% of 1,8-cineole were present, respectively. (E)-Nerolidol was identified in larger quantities in the leaf essential oil (7.6% and. 3.5%). The pseudostem oil sample contained an appreciably higher content of hexadecanoic acid (1.9%) than the leaf oil (0.9%). However, n-pentacosane was present only in the leaf oil sample.
There are instances of particular compounds where both the leaf and pseudostem oil samples contained nearly or equal quantitative amounts. These can be seen in Table 1, where α-selinene represented 1% in both oil samples, whereas δ-cadinene formed 0.49% (pseudostem oil) and 0.47% (leaf oil). In addition, hinesol was present in 0.20% of the pseudostem oil and 0.21% of the leaf oil. Other examples in which both the leaves and pseudostem oil samples contained nearly or equal quantitative amounts of particular compounds could be found in γ-terpinene, pinocarvone, aromadendrene, and eudesm-7(11)-en-4-ol (Table 1).
The chemical composition of essential oils of the pseudostem and leaves of M tomrey was compared with available data on essential oil constituents of other Meistera species. The presence of α-pinene and β-pinene in M tomrey is noteworthy. These 2 compounds feature prominently in the essential oil of Meistera species and the 2 are among the significant constituents of the leaf of M sudae, 7 M caudata,8,9 and M cristatissima, 10 as well as the rhizomes of M caudata. 8 However, some compounds, such as camphene, β-elemene, α-selinene, and β-selinene in M caudata, occurred in lower quantities in M tomrey. Also, the essential oils of M tomrey contained a lower amount of caryophyllene oxide and spathulenol when compared with M cristatissima. 10 More importantly, myrcene and limonene found in the essential oils of M sudae 7 and δ-3-carene 8 and bicyclogermacrene 9 identified in M caudata were conspicuously absent in M tomrey. More data are required to substantiate the importance of α-pinene and β-pinene as chemotaxonomic markers of Meistera essential oils from Vietnam.
Conclusions
For the first time, the chemical compositions of essential oils from M tormey were reported. Monoterpenes and sesquiterpenes were the main classes of compounds identified in the essential oils of the pseudostem and leaves of M tormey. In addition, monoterpenes constituted the main compounds of the essential oils. These are β-pinene (14.2%), 1,8-cineole (13.5%), and α-pinene (6.9%) from the pseudostem oil sample; as well as β-pinene (6.6%), 1,8-cineole (16.7%), α-pinene (4.6%), and borneol (4.2%) in the leaf essential oil. Notably, within the leaf essential oil, (E)-nerolidol (7.6%) emerged as the most prominent sesquiterpene.
Materials and Methods
Plant Materials
The fresh leaves and pseudostem (1.0 and 1.0 kg) of M tomrey were collected from Bao Lam district, Lam Dong province (GPS: 11°42'52.8"N 107°38'27.3"E) in April 2022. The plant samples were identified by Mr Nguyen Danh Duc and Dr Le Tuan Anh, Vietnam National Museum of Nature. A voucher specimen (MT-D49) was deposited at the Faculty of Pharmacy, Hue University of Medicine and Pharmacy, Hue University, Vietnam.
Hydrodistillation of the Essential Oils
To prepare for hydrodistillation, we followed the methods established in previous studies.6,12 The fresh pseudostem and leaf samples of M tomrey were shredded separately.
For the pseudostem and leaves, fresh material (1.0 kg each) was subjected to hydrodistillation using a Clevenger-type apparatus. The pulverized sample of each plant was divided into 3 equal parts to enable the distillation of essential oils 3 times. Each of the samples was packed separately inside a 2-L flask. The samples were submerged completely inside the flask with enough distilled water (1.2-L), and then connected to the Clevenger-type apparatus. The essential oils were allowed to distill for 3 h after the whole apparatus had been connected to a heating mantle maintained at normal pressure according to Vietnamese Pharmacopoeia. 13 On completion, the hydrodistilled essential oils were collected, dried with sodium sulfate, and stored in a refrigerator at 4 °C. The experiments were repeated 3 times. The yield (%) of the essential oils was calculated separately by dividing the mass (g) of the essential oil by the mass (g) of the pulverized pseudostem and leaves of M tomrey, as described previously.6,12
Analysis of the Essential Oils
The chemical composition of the essential oil was analyzed using the GCMS-QP2010 Plus system, manufactured by Shimadzu in Kyoto, Japan. The system was equipped with an Equity-5 capillary column measuring 30 m in length and 0.25 mm in diameter, coated with a 0.25-µm film thickness, and coupled with a mass spectrometer (MSD QP2010 Plus) for GC/MS analysis. To carry out the analysis, each of the essential oils was first diluted with n-hexane at a ratio of 1:100. Thereafter, 1 μL of each of the diluted oil was introduced separately into the GC/MS column. Helium was used as the carrier gas at a flow rate of 1.5 mL/min, while the injector and interface temperatures were set at 280 °C. The column temperature was programmed to increase from 60 °C (2 min hold) to 240 °C at a rate of 3 °C/min (10 min hold), followed by an increase to 280 °C at a rate of 5 °C/min (40 min hold). The samples were injected in splitless mode. The mass spectrometer was set to an ionization voltage of 70 eV and an acquisition scan mass range of 45 to 500 (m/z) at a sampling rate of 1.0 scan/s.
Identification of Terpenes and Nonterpene Compounds of the Essential Oils
The constituents’ retention indices (RIs) were established by co-injecting a reference homologous series of n-alkanes (C8-C38) under the same conditions. The identification of components was carried out by comparing their RI values with those reported by Adams, 14 and further identification was performed by comparing their mass spectra with those stored in the GC/MS database from NIST 11 15 and WILEY seventh. Quantification was done by using the relative peak area percentage. See Supplemental Material for further information.
Supplemental Material
sj-docx-1-npx-10.1177_1934578X231186019 - Supplemental material for Chemical Composition of Essential Oils From the Pseudostem and Leaves of Meistera tomrey Growing in Vietnam
Supplemental material, sj-docx-1-npx-10.1177_1934578X231186019 for Chemical Composition of Essential Oils From the Pseudostem and Leaves of Meistera tomrey Growing in Vietnam by Tuan Quoc Doan, Duc Danh Nguyen, Hoai Thi Nguyen and Isiaka Ajani Ogunwande in Natural Product Communications
Footnotes
Acknowledgments
This research was supported by Hue University (no. DHH2022-04-177).
Authors’ Contributions
The research idea was provided by DQ Tuan and NT Hoai. Extraction and analysis were carried out by DQ Tuan. Reading and revising the manuscript were undertaken by DQ Tuan, ND Duc, NT Hoai, and IA Ogunwande.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the This research was funded by Hue University (grant no. DHH2022-04-177).
Ethical Approval
Not applicable, because this article does not contain any studies with human or animal subjects.
Statement of Human and Animal Rights
This article does not contain any studies with human or animal subjects.
Informed Consent
There are no human subjects in this article and informed consent is not applicable.
Trial Registration
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Supplemental Material
Supplemental material for this article is available online.
References
Supplementary Material
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