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Abstract

The essential oils from different parts of Thuja plicata and its cultivar varieties “Fastigiata”, “Kornik,” and “Zebrina” were analyzed by gas chromatography (GC) and GC/mass spectrometry. More than 80 compounds were identified. The oils from leaves, twigs with leaves, and twigs without leaves contained mainly α-thujone (52.1%-59.2%), fenchone (10.0%-11.3%), and beyerene (3.7%-9.5%), whereas in the cone oil there were α-thujone (35.6%), sabinene (24.0%), and α-pinene (8.3%). The main constituents of the oils from twigs with leaves of “Fastigiata,” “Zebrina,” and “Kornik” cultivars were α-thujone (76.2%, 72.5%, and 67.4%, respectively) and β-thujone (7.6%, 6.2%, and 4.9%, respectively). The oils from cultivars contained more thujones and less fenchone and diterpenes in comparison with T. plicata oil.

Keywords

essential oil composition α-thujone

Thuja plicata Donn ex D. Don (T. gigantea Nutt., Cupressaceae), commonly known as western red cedar or giant arborvitae, is a large (50 m height), coniferous tree with a pyramidal habit, horizontal branches, flattened twigs, evergreen, scale-like, aromatic leaves and small cones. The species is native to the Pacific coast of North America. In the 19th century it was introduced to European forests. Its wood is used for timber, mainly to produce outdoor furniture.^1
-3 Many cultivars of T. plicata exist, showing great variation in shape, size, and foliage color. They are widely planted as ornamental trees in parks, and as hedges or screens in domestic gardens. The most popular varieties in Poland are T. plicata “Fastigiata,” T. plicata “Kornik,” and T. plicata “Zebrina.”¹

Essential oil from the foliage of T. plicata (western red cedar leaf oil) is commercially produced in Canada and the United States. It is traditionally used as a natural insect repellent and as a safe, green, broad-spectrum antifungal agent to preserve wood and prevent contamination in buildings. Because of its intensive, pleasant, green-herbal aroma it is used in perfumes, deodorants, room sprays, cleansers, disinfectants, shoe polishes, and skin care cosmetics, such as soaps, hair preparations, and hand creams. There are only a limited number of papers that describe T. plicata essential oil, its chemical composition,^4

-10 and its antimicrobial^9
-11 and anti-inflammatory activities.¹² In all investigated leaf oils no more than 40 components were identified with α-thujone (47.8%-82.5%), β-thujone (6.3%-8.8%), fenchone (0%-15.1%), sabinene (2.3%-6.4%), terpinen-4-ol (1.6%-4.7%), and beyerene (0%-4.6%) as the main constituents. The quantitative composition of the oils varied significantly, depending on the plant origin,^4-7,9,10 age of the tree,^4,6 and harvest season.⁴ The heartwood oil was quite different in composition. It contained mainly C₁₁- ester, 1,4-cineole, fenchol, γ-eudesmol, thujic acid and α-, β- and γ-thujaplicin.⁸

Our paper presents a detailed chemical composition of the essential oils from twigs with leaves (it is typical source for almost all commercial conifer oils), leaves, twigs without leaves, and cones. This is the first data on the cone oil of this species, as well as oils of its cultivars “Fastigiata,” “Kornik,” and “Zebrina.” The yields (averages of 3 replicates) and chemical composition of the oils are presented in Table 1. Leaves of T. plicata contained several times more oil than twigs without leaves (0.8% and 0.2%, respectively). Cones contained 1.2% of the oil. “Fastigiata” and “Zebrina” cultivars were about 2 times richer in oil than T. plicata (1.6%, 1.2%, and 0.7%, respectively). More than 80 compounds representing 96% to 99% of the oils were identified, with about 40 for the first time in this species. The composition of the oils from leaves, twigs with leaves, and twigs without leaves of T. plicata were similar. The main constituents of the oils were α-thujone (52.1%-59.2%), fenchone (10.0%-11.3%), and beyerene (3.7-9.5). A few components were present in concentrations of 2%-5%: sabinene, β-thujone, camphor, terpinen-4-ol, and bornyl acetate, while others constituted less than 1%. The oil from cones differed in composition. In comparison with those oils, it contained lower amounts of α-thujone (35.6%), fenchone (3.8%), and beyerene (0.3%), but the amounts of the monoterpene hydrocarbons sabinene (24.0%) and α-pinene (8.3%) were much higher. Additionally, it contained many sesquiterpenes and diterpenes, which were not found in the oil from leaves and twigs. Thus, both leaves and twigs with leaves give oils rich in thujones. The presence of cones in the raw material may reduce the content of thujones in the oil.

Table 1

Chemical Composition of the Essential Oils From Thuja Plicata Twigs With Leaves (A), Leaves (B), Twigs Without Leaves (C), Fruits (D), T. Plicata Cv. “Fastigiata” (E), T. Plicata Cv. “Kornik” (F), and T. Plicata Cv. “Zebrina” (G).

Compound	RI	LRI	Percentage
Compound	RI	LRI	A	B	C	D	E	F	G
(Z)-Salvene	843	849	tr	0.1	0.1	tr	0.3	tr	0.2
Santolinatriene	897	909	0.1	0.1	tr	tr		tr
Tricyclene	922	927	tr	tr	tr	tr	tr	tr	tr
α-Thujene	925	932	0.4	0.4	0.2	0.8	0.3	0.2	0.4
α-Pinene	928	936	1.1	1.0	0.6	8.3	1.1	1.0	1.4
α-Fenchene	939	941	0.8	0.7	0.5	0.4	tr	0.4	tr
Camphene	944	950	0.7	0.7	0.5	0.5	tr	0.4	tr
Sabinene	968	973	5.3	5.6	1.9	24.0	4.8	3.0	7.1
β-Pinene	970	978	0.1	0.1	0.1	0.3	0.1	0.1	0.1
Myrcene	982	987	1.2	1.1	0.2	3.2	1.4	1.1	1.8
α-Phellandrene	994	1002	tr	tr	tr	0.1	tr	tr	tr
α-Terpinene	1006	1013	0.4	0.3	0.2	0.6	0.4	0.3	0.4
p-Cymene	1009	1015	0.3	0.3	0.6	0.3	0.3	0.3	0.3
β-Phellandrene	1018	1023				0.1
Limonene	1020	1025	1.2	1.1	0.7	1.5	0.8	1.0	0.9
γ-Terpinene	1047	1051	0.5	0.4	0.5	0.9	0.6	0.5	0.6
trans-Sabinene hydrate	1051	1053	0.4	0.5	0.4	0.5	0.3	0.3	0.4
Fenchone	1068	1069	11.3	10.6	10.0	3.8	tr	7.5	0.1
Terpinolene	1078	1082	0.1	0.1	0.1	0.3	0.2	0.2	0.3
α-Thujone	1090	1089	53.8	52.1	59.2	35.6	76.2	67.4	72.5
β-Thujone	1096	1103	3.4	3.4	3.7	3.1	7.6	4.9	6.2
α-Campholenal	1101	1105	0.1	0.1	0.1	0.1		tr
cis-p-Menth-2-en-1-ol	1104	1108	0.3	0.3	0.3	0.2	0.1	0.3	0.1
trans-p-Menth-2-en-1-ol	1116	1116	0.2	0.2	0.2	0.2	0.1	0.1	0.1
Camphor	1119	1123	2.1	2.0	2.1	0.8	0.1	0.3	0.1
Sabina ketone	1128	1132	0.1	0.1	0.1	tr	0.1	0.1	0.1
trans-Verbenol	1132	1136	0.1	0.1	0.1	0.1	0.1	tr	0.1
Camphene hydrate	1136	1143	0.2	0.2	0.3	0.1		0.2	0.1
Thujol	1145	1149	0.1	0.1	0.2	0.1	0.3	0.1	0.3
Borneol	1147	1150	0.8	0.6	0.6	0.2	tr	0.1	0.1
Terpinen-4-ol	1161	1164	1.8	1.5	2.1	1.8	2.4	1.9	1.9
α-Terpineol	1170	1176	0.2	0.1	0.2	0.1	0.1	0.2	0.1
Myrtenol	1174	1178	tr	tr	tr	tr	0.3		0.5
Verbenone	1177	1183	0.1		0.1	tr		tr
trans-Piperitol	1188	1193	tr	0.1	tr	tr	tr	tr	tr
trans-Carveol	1196	1200	tr	tr	tr			tr
Fenchyl acetate	1202	1205	0.1	0.1	0.2	0.1		0.1
Thymol methyl ether	1212	1215	tr	tr	tr	tr		tr
Carvacrol methyl ether	1224	1227	tr	tr	tr	tr	tr	tr	tr
cis-Sabinene hydrate acetate	1248	1248	0.1	0.1	0.2	0.1	tr	0.1	tr
trans-Sabinene hydrate acetate	1254	1254	0.1	0.1	0.1	0.1	0.1	0.1	0.1
Bornyl acetate	1268	1270	1.8	1.8	2.4	0.8	tr	2.1	0.1
trans-Sabinyl acetate	1272	1278	tr	tr	tr	0.1	tr	tr	0.1
Neothujyl acetate	1275	1278^a	0.3	0.3	0.3	0.2	0.1	0.2	0.1
Menthyl acetate	1277	1280	0.1	0.1	0.1	0.1	0.2	0.1	0.2
Terpinen-4-yl acetate	1283	1289	tr	tr	0.1	0.1	0.1	tr	0.1
α-Terpinyl acetate	1331	1335	1.0	1.0	0.9	0.8	0.2	0.6	0.2
α-Cubebene	1348	1355				0.1			tr
Geranyl acetate	1361	1362	tr	tr			tr	0.1	tr
α-Copaene	1378	1379				tr			tr
β-Elemene	1387	1389				0.5			tr
(E)-β-Caryophyllene	1417	1421				0.1		tr	tr
Guaia-6,9-diene	1438	1443	tr	tr		0.8			tr
(E)-β-Farnesene	1446	1446				0.1
α-Humulene	1452	1455				0.1		tr	tr
Germacrene D	1475	1479				0.1			tr
α-Muurolene	1492	1496				0.1
γ-Cadinene	1505	1507	tr	tr		0.1	tr		tr
δ-Cadinene	1515	1520	tr	0.1		0.1	tr	tr	0.1
Elemol	1538	1541				0.1		tr
Furopelargone B	1561	1567^b	0.3	0.3	0.4	0.2	tr	0.2	0.1
Germacrene D-4-ol	1566	1571	0.1	0.1		0.5	tr	tr	0.1
Caryophyllene oxide	1571	1578	0.1	0.1	0.1	0.1	tr	0.4	tr
β-Oplopenone	1589	1595	tr	tr	tr		tr	tr	tr
Humulene epoxide II	1594	1602	tr	tr	0.1	0.1	tr	0.1	tr
epi-α-Muurolol	1626	1633	tr	tr		0.1	tr	tr	0.1
α-Cadinol	1638	1643	0.1	0.1		0.3	tr	tr	0.1
14-Hyrdoxy-β-caryophyllene	1652	1656				0.1			tr
Oplopanone	1706	1703^c	tr	tr	tr	0.1		tr	tr
Rimuene	1896	1907	1.3	1.7	0.6	0.1	0.1	0.9	0.2
Beyerene	1944	1951	6.7	9.5	3.7	0.3	0.3	2.2	0.4
Pimara-8(14),15-diene	1950	1955	tr	tr	tr	tr		tr
Sandaracopimara-8(14),15-diene	1964	1967^d	0.1	0.1	0.1
Manool oxide	1999	2007	tr	tr	tr	tr
(E)-Biformene	2002	2008				0.1
Kaur-15-ene	2006	2011	tr	tr	tr		tr	tr	tr
Abieta-8,12-diene	2017	2022^a				0.2
Abietatriene	2039	2046	0.1	0.1	0.1	0.1	tr	tr	tr
Abieta-7,13-diene	2079	2084	tr	tr	0.1	0.7		tr
Abieta-8(14),13(15)-diene	2147	2152				0.1			tr
Abieta-6(8),14-dien-18-al	2213	2215^e				0.3
Dehydroabietal	2234	2241^f				0.1
cis-Totarol	2249	2252	tr	tr	0.7
Abietal	2256	2261	tr		0.1	1.3			0.1
Beyeren-19-yl acetate	2308						0.1	0.6	1.2
4-epi-Abietol	2329	2341^a				0.4
Abieta-8,13(15)-dien-18-al	2340	2347^e				0.1
Abietol	2378	2389^e				0.3
Total			99.5	99.6	96.2	98.2	99.2	99.7	99.3
Monoterpene hydrocarbons			12.2	12.0	6.2	41.3	10.3	8.5	13.5
Oxygenated monoterpenes			78.5	75.5	84.0	49.1	88.4	86.8	83.4
Sesquiterpene hydrocarbons			tr	0.1		2.0	tr	tr	0.1
Oxygenated sesquiterpenes			0.6	0.6	0.6	1.7	tr	0.7	0.4
Diterpene hydrocarbons			8.2	11.4	4.6	1.6	0.4	3.1	0.6
Oxygenated diterpenes			tr	tr	0.8	2.5	0.1	0.6	1.3
Oil yield			0.7	0.8	0.2	1.2	1.6	0.8	1.2

LRI, literature retention indices on DB-1 column according to MassFinder 3.1; RI, retention indices on Rtx-1 column; tr, trace (<0.05%).

^aLiterature retention indices on DB-5 column according to Adams.¹³

^b-fLiterature retention indices according to NIST (^bBP-1 column, ^cHP-1 column, ^dCP Sil 5 column, ^eHP-5 column, ^fDB-1 column).

The oils of “Fastigiata” and “Zebrina” varieties had similar composition with α-thujone (76.2% and 72.5%, respectively), β-thujone (7.6% and 6.2%, respectively), and sabinene (4.8% and 7.1%, respectively) as the main constituents. “Kornik” oil contained α-thujone (67.4%), fenchone (7.5%), and β-thujone (4.9%). The chemical profiles of the oils from twigs with leaves of T. plicata and its cultivars “Fastigiata,” “Kornik,” and “Zebrina” were comparable having α-thujone as the dominant compound. On the other hand, significant differences between the oils were observed. The oils of “Fastigiata” and “Zebrina” in comparison with T. plicata oil contained more thujones (78%-83% and 57%, respectively) and less fenchone (trace and 11%, respectively) and diterpenes (1% and 8%, respectively).

With regard to the previously reported T. plicata oils, the composition of “Fastigiata” and “Zebrina” oils were similar to that of laboratory distilled Canadian oils^4
-6 and commercial oil from the United States,⁷ with high level of α-thujone (72%-82%), no fenchone, and no diterpenes. In turn, the T. plicata oil investigated by us resembled commercial Canadian oil⁹ with similar contents of α-thujone (54%), fenchone (15%), and β-thujone (6%-8%), but differed in the content of diterpenes. Such high levels of diterpenes were previously found only in the oil from T. plicata var. “Gracilis.”¹⁰

Our investigation showed that the yield and quantitative composition of T. plicata oil depended on the plant organ and variety. Twigs with leaves of T. plicata, particularly from “Fastigiata” and “Zebrina” cultivars, due to their high amount of essential oil and high content of thujones can be a good source of natural thujones for the pharmaceutical and fragrance industries.

Experimental

Plant Material

Thuja plicata Donn ex D. Don and its cultivars “Fastigiata,” “Kornik,” and “Zebrina” were collected in the Lodz Botanical Garden, Poland, in October 2016. The voucher specimens (Tpl/2016, Tplf/2016, Tplk/2016 and Tplz/2016) have been deposited in the Herbarium of the Institute of General Food Chemistry, Lodz University of Technology.

The fresh branches of T. plicata were divided into twigs with leaves, leaves, twigs without leaves, and cones. These samples of fresh plant material (100.0 g each), as well as twigs with leaves of “Fastigiata,” “Kornik,” and “Zebrina” cultivars were cut into small pieces (to 0.5 cm long) and separately hydrodistilled in a Clevenger-type apparatus for 3 hours to obtain essential oils. The procedure was replicated 3 times. After decanting and drying over anhydrous MgSO₄, the oils were stored at low temperature (5°C) before analysis. The oils had pale yellow color and an intensive herbal-camphoraceous aroma.

Analysis of the Essential Oils

The chemical composition of the oils was determined by simultaneous gas chromatography (GC)/flame ionization detection (FID) and GC/mass spectrometry (MS) analyses using an MS-FID splitter (SGE Analytical Science) and a Trace GC ultra gas chromatograph coupled with a DSQ II mass spectrometer (Thermo Electron Corporation). The apparatus was equipped with an apolar capillary column Rtx-1 (dimethylpolysiloxane), 60 m × 0.25 mm × 0.25 µm film thickness (Restek, Bellafonte, PA, USA). The oven temperature was programmed from 50 to 300°C with rises of 4°C/min. Injector temperature was 280°C, detector temperature 300°C, ion source temperature 200°C, carrier gas helium with constant pressure 300 kPa, ionization voltage 70 eV, mass range 33-420 amu.

Identification of components was based on comparison of their retention indices relative to n-alkanes (C₈-C₂₆) and their mass spectra with those of commercial libraries (MassFinder 3.1, NIST 98.2, Wiley Registry of Mass Spectral Data 8th ed.) and literature.¹³

A quantitative analysis (expressed as percentage of each component) was carried out by peak normalization measurement without correction factors.

Footnotes

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) declared no financial support for the research, authorship, and/or publication of this article.

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Chemical Composition of the Essential Oils From Twigs,Leaves,and Cones of Thuja plicata and Its Cultivar Varieties “Fastigiata”,“Kornik,” and “Zebrina”