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Article

Chemical Compositions and Enantiomeric Distributions of Foliar Essential Oils of Chamaecyparis lawsoniana (A. Murray bis) Parl, Thuja plicata Donn ex D. Don, and Tsuga heterophylla Sarg.

by
Elizabeth Ankney
1,
Kathy Swor
2,
Ambika Poudel
3,
Prabodh Satyal
3,
Joyce Kelly R. da Silva
4 and
William N. Setzer
3,5,*
1
Independent Researcher, 141 W. 17th St., Lafayette, OR 97127, USA
2
Independent Researcher, 1432 W. Heartland Dr., Kuna, ID 83634, USA
3
Aromatic Plant Research Center, 230 N 1200 E, Suite 100, Lehi, UT 84043, USA
4
Laboratório de Biotecnologia de Enzimas e Biotransformações, Universidade Federal do Pará, Belém 66075-110, Brazil
5
Department of Chemistry, University of Alabama in Huntsville, Huntsville, AL 35899, USA
*
Author to whom correspondence should be addressed.
Plants 2024, 13(10), 1325; https://doi.org/10.3390/plants13101325
Submission received: 16 April 2024 / Revised: 2 May 2024 / Accepted: 9 May 2024 / Published: 11 May 2024
(This article belongs to the Special Issue Phytochemistry of Aromatic and Medicinal Plants)
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Versions Notes

Abstract

:
As part of our continuing interest in the essential oil compositions of gymnosperms, particularly the distribution of chiral terpenoids, we have obtained the foliar essential oils of Chamaecyparis lawsoniana (two samples), Thuja plicata (three samples), and Tsuga heterophylla (six samples) from locations in the state of Oregon, USA. The essential oils were obtained via hydrodistillation and analyzed by gas chromatographic techniques, including chiral gas chromatography—mass spectrometry. The major components in C. lawsoniana foliar essential oil were limonene (27.4% and 22.0%; >99% (+)-limonene), oplopanonyl acetate (13.8% and 11.3%), beyerene (14.3% and 9.0%), sabinene (7.0% and 6.5%; >99% (+)-sabinene), terpinen-4-ol (5.0% and 5.3%; predominantly (+)-terpinen-4-ol), and methyl myrtenate (2.0% and 5.4%). The major components in T. plicata essential oil were (−)-α-thujone (67.1–74.6%), (+)-β-thujone (7.8–9.3%), terpinen-4-ol (2.7–4.4%; predominantly (+)-terpinen-4-ol), and (+)-sabinene (1.1–3.5%). The major components in T. heterophylla essential oil were myrcene (7.0–27.6%), α-pinene (14.4–27.2%), β-phellandrene (6.6–19.3%), β-pinene (6.4–14.9%; >90% (−)-β-pinene), and (Z)-β-ocimene (0.7–11.3%). There are significant differences between the C. lawsoniana essential oils from wild trees in Oregon and those of trees cultivated in other geographical locations. The essential oil compositions of T. plicata are very similar, regardless of the collection site. There are no significant differences between T. heterophylla essential oils from the Oregon Coastal Range or those from the Oregon Cascade Range. Comparing essential oils of the Cupressaceae with the Pinaceae, there are some developing trends. The (+)-enantiomers seem to dominate for α-pinene, camphene, sabinene, β-pinene, limonene, terpinen-4-ol, and α-terpineol in the Cuppressaceae. On the other hand, the (−)-enantiomers seem to predominate for α-pinene, camphene, β-pinene, limonene, β-phellandrene, terpinen-4-ol, and α-terpineol in the Pinaceae.

1. Introduction

Chamaecyparis Spach is a genus in the Cupressaceae. The World Flora Online currently recognizes seven species of the genus [1], namely, Chamaecyparis flifera Veitch ex. Sénécl., Chamaecyparis formosensis Matsum. (Formosan cypress, endemic to Taiwan), Chamaecyparis hodginsii (Dunn) Rushforth (Po mu, found in eastern China and Vietnam), Chamaecyparis lawsoniana (A. Murray bis) Parl. (Port Orford cedar, found in western North America), Chamaecyparis obtusa (Siebold & Zucc.) Endl. (hinoki cypress, native to Japan), Chamaecyparis pisifera (Siebold & Zucc.) Endl. (Sawara cypress, native to Honshu and Kyushi, Japan), and Chamaecyparis thyoides (L.) Britton, Sterns & Poggenb. (Atlantic white cedar, found in the eastern United States) [2,3].
The genus Thuja L. (Cupressaceae) is represented by five taxa [4]: Thuja koraiensis Nakai (found in Jilin Province of China and in North and South Korea) [5], Thuja occidentalis L. (in eastern North America, the tree ranges from southeastern Canada, Minnesota, Michigan, and New England, south through the Appalachian Mountains) [6], Thuja plicata Donn ex. D. Don (two populations in western North America, a coastal population ranging from the Alaskan panhandle, coastal British Columbia south into coastal northern California, and an inland population found in the Rocky Mountains of British Columbia heading south to northern Idaho and western Montana) [7], Thuja standishii (Gordon) Carrière (native to Japan) [8], and Thuja sutchuenensis Franch. (native to Sichuan Province, China, but probably extinct in the wild due to deforestation) [9]. The genus has been important to the traditional healthcare systems in its natural ranges [10,11].
The genus Tsuga (Endl.) Carrière, in the family Pinaceae, is represented by five North American taxa, namely Tsuga canadensis (L.) Carrière (found in eastern North America), Tsuga caroliniana Engelm. (native to the Appalachian Mountains), Tsuga heterophylla (Raf.) Sarg. (found in western North America), Tsuga mertensiana (Bong.) Carrière (found in western North America), Tsuga jeffreyi (A. Henry) A. Henry (syn. Tsuga mertensiana subsp. jeffreyi (A. Henry) Silba) [12]; and seven East Asian species, Tsuga chinensis (Franch.) Pritz. (native to China, Taiwan, Tibet, and Vietnam), Tsuga diversifolia (Maxim.) Mast. (native to the Japanese islands of Honshū, Kyūshū, and Shikoku), Tsuga dumosa (D. Don) Eichler (native to the eastern Himalayas), Tsuga forrestii Downie (syn. Tsuga chinensis var. forrestii (Downie) Silba, found in the northeast Guizhou, southwest Sichuan, and northwest Yunnan provinces of China), Tsuga sieboldii (Siebold & Zucc.) Carrière (native to the Japanese islands of Honshū, Kyūshū, Shikoku, and Yakushima), Tsuga thuja A. Murray, and Tsuga ulleungensis G.P. Holman, Del Tredici, Havill, N.S. Lee & C.S. Campb. (endemic to Ulleungdo island, Korea) [13,14].
Chamaecyparis lawsoniana (A. Murray bis) Parl., Cupressaceae (Port Orford cedar) is a large tree, around 50 m tall with a trunk up to 3 m in diameter [15]. The foliage has a lacy feathery appearance with leaves that are overlapping and scalelike, 2–3 mm long; the bark is thick, silvery-brown, and furrowed (Figure 1) [16]. The natural range of C. lawsoniana is limited to a small area of coastal Oregon into northern California (Figure 2) [17]. It has become an important ornamental outside of its natural range, particularly in Europe. Previous essential oil analyses have been carried out on C. lawsoniana cultivated in Japan [18], Belgium [19], Egypt [20,21], Iran [22], Spain [23], and Greece [24]. A purpose of the present study is to characterize the foliar essential oil of C. lawsoniana growing in its natural habitat in the Oregon Coastal Range.
Thuja plicata Donn ex D. Don, Cupressaceae (western red cedar) is a large tree, growing up to 75 m tall with a trunk up to 5 m in diameter; the thick, fibrous, fissured bark is reddish-brown or grayish-brown; the foliage is displayed as flat, pendant sprays with overlapping scale-like leaves (Figure 3) [26]. There are two separate ranges of T. plicata, a Coast–Cascade portion from southeastern Alaska (56°30′ N) to northwestern California (40°30′ N), and a Rocky Mountain section from British Columbia (54°30′ N) to Idaho and Montana (45°50′ N) (Figure 4) [26].
The heartwood of T. plicata has been shown to be a source of tropone monoterpenoids [27,28,29,30,31] and lignans [32,33,34,35,36,37,38,39,40], and the dilactone thujin [41], while the bark and aerial parts have yielded diterpenoid derivatives [42,43]. There have been several investigations on the foliar essential oil compositions of T. plicata growing wild in western North America [44,45], cultivated in Poland [46,47], cultivated in Serbia [48], and growing wild in Idaho, USA [49]. In addition, the volatiles from resin extracts of T. plicata cultivated in Czechia have been reported [50]. In this work, we had the opportunity to collect T. plicata samples from the Cascade Range of Oregon, so an additional purpose of this study is to test the hypothesis that the T. plicata from Oregon, a separate population from those from Idaho, presents differences in essential oil composition.
Tsuga heterophylla Sarg. (western hemlock) is a tree that grows up to 50 m tall with a trunk diameter up to 2 m; its leaves are needles, 5–20 mm long and 1.5–2 mm wide; its cones are small, 15–25 mm long and 10–25 mm wide; its bark is grey-brown, scaly, and moderately fissured (Figure 5) [51]. The native range of T. heterophylla is from the coast of southern Alaska, south through coastal British Columbia, Washington, Oregon, and into coastal northern California (Figure 6) [52]. The coastal range of T. heterophylla divides into an Oregon Coastal Range and a Cascade Range in Oregon. There is also a Rocky Mountain population that ranges from British Columbia south to northern Idaho and northwestern Montana (Figure 6).
Extracts of the wood of T. heterophylla have yielded lignans, including matairesinol [53], 8-hydroxy-α-conidendrin, 8-hydroxy-α-conidendric acid methyl ester [54], and 8-hydroxyoxomatairesinol [55]. Foliar volatiles have also been examined [56,57,58]. The purpose of the current study is to obtain foliar essential oils of T. heterophylla from both the Oregon Coastal Range and the Oregon Cascades to compare essential oil compositions from the two separated populations as well as to compare with compositions previously reported from British Columbia, Canada.

2. Results and Discussion

2.1. Essential Oil Compositions

2.1.1. Chamaecyparis lawsoniana

The two C. lawsoniana pale yellow essential oils were obtained in 1.90% and 2.33% yields. Gas chromatographic analysis led to the identification of 136 components, which accounted for 97.3% and 96.8% of the total essential oil compositions (Table 1). The major components in the foliar essential oils were limonene (27.4% and 22.0%), oplopanonyl acetate (13.8% and 11.3%), beyerene (14.3% and 9.0%), sabinene (7.0% and 6.5%), terpinen-4-ol (5.0% and 5.3%), and methyl myrtenate (2.0% and 5.4%). There have been several reports on the essential oil compositions of C. lawsoniana cultivated outside the natural range of the tree, namely those cultivated in Japan [18], Belgium [19], Iran [22], Spain [23], Greece [24], and Egypt [20,21]. Not surprisingly, the essential oil compositions show wide variation, which can be attributed to the different geographical locations of these cultivated individuals.
In order to visualize the differences in composition, a hierarchical cluster analysis (HCA) was carried out based on the percentages of the 30 most abundant components (Figure 7), and four clusters were identified. Cluster 1 grouped the cultivated sample, the sample from Greece, with the most remarkable similarity (91.6%) to the wild individuals due to the moderate amounts of limonene (18.5–27.4%), followed by oplopanonyl acetate (11.3–15.9%), and beyerene (9.0–17.1%). In addition, Cluster 1 showed a similarity of 74.3% with the samples from Spain, Belgium, and Japan (Cluster 2), which displayed high amounts of limonene as a major compound (57.6–77.7%). The individual cultivated in Iran (Cluster 3) was rich in cis-abienol (23.5%), trans-ferruginol (14.3%), α-cadinol (8.8%) and cis-muurola-4(14),5-diene (8.6%), while the sample from Egypt (Cluster 4) showed terpinen-4-ol (22.0%) and sabinene (21.0%) as significant compounds. For this reason, these samples displayed only slight similarity with the Oregon C. lawsoniana essential oils.
A principal component analysis (PCA) was applied to the constituents present to evaluate the chemical variety among the C. lawsoniana samples. The F1 and F2 of the constituents of oil samples explained 81.12% of the chemical variability, and the results corroborated the HCA analysis by grouping the samples into four main groups (Figure 8). Among the compounds with amounts above 5%, F1 showed positive correlations with limonene (11.267), oplopanonyl acetate (2.627), beyerene (2.448), sabinene (0.826), terpinen-4-ol (0.739), and methyl myrtenate (0.424), and negative correlations with cis-abienol (−1.380) and trans-ferruginol (−1.191). On the other hand, the F2 component explained 15.76% of the chemical variability, presenting positive correlations with sabinene (2.894), terpinen-4-ol (2.850), beyerene (0.909), γ-terpinene (0.898), oplopanonyl acetate (0.868) and camphor (0.830), and negative correlations with cis-abienol (−2.861), trans-ferruginol (−1.761), limonene (−1.562), α-cadinol (−1.064), and cis-muurola-4(14),5-diene (−1.006).

2.1.2. Thuja plicata

The hydrodistillation of T. plicata foliage gave colorless-to-pale-yellow essential oils in yields of 0.76–1.03%. Gas chromatographic analysis led to the identification of 91 components, which accounted for 98.7% of the composition in each sample (Table 2). The major components in the essential oils were α-thujone (67.1–74.6%), β-thujone (7.8–9.3%), terpinen-4-ol (2.7–4.4%), and sabinene (1.1–3.5%).
The essential oil compositions of the Oregon T. plicata samples were very similar to those from our previous collection from northern Idaho [49] as well as those reported by von Rudloff and co-workers [44], Tsiri and co-workers [46], Lis and co-workers [47], and Nikolić and co-workers [48]. Indeed, a hierarchical cluster analysis (HCA) reveals very high similarity between the samples (Figure 9). The cluster analysis shows the greatest similarity, not surprisingly, between the samples from western North America (>99.94% similarity). Even the samples cultivated in Poland [47] showed >99.59% similarity to the North American samples. In comparing the Oregon samples from this work with those of our previous investigation of samples from Idaho, the concentrations of the major components are not statistically different (t-test, p > 0.05) (Figure 10). However, the β-thujone t-test showed a p-value of 0.057. In retrospect, the similarities in essential oil compositions are consistent with the genomic analysis of T. plicata; there is little genetic differentiation in this species [64,65,66].
The T. plicata samples were subjected to principal component analysis (PCA) to understand their chemical variability comprehensively. The results, which are highly precise, revealed that F1 and F2 accounted for a significant 99.99% of the entire chemical variability. This analysis effectively grouped the samples into four main categories, as illustrated in Figure 11. F1 demonstrated a positive correlation with α-thujone (6.695), while terpinen-4-ol (−2.430), sabinene (−2.344), and β-thujone (−1.921), showed negative correlations. On the other hand, F2 had a positive correlation with sabinene (0.206), but a negative correlation only with β-thujone (−0.170). Notably, the samples collected in Oregon and those from Idaho and von Rudloff were found to have similar chemical characteristics, with α-thujone concentrations close to 70% and sabinene amounts of less than 5.0%.

2.1.3. Tsuga heterophylla

The hydrodistillation of the foliage from the six T. heterophylla trees yielded colorless essential oils with yields of 5.28% to 7.75%. Monoterpene hydrocarbons dominated the essential oils of the T. heterophylla, with myrcene (7.0–27.6%), α-pinene (14.4–27.2%), β-phellandrene (6.6–19.3%), β-pinene (6.4–14.9%), and (Z)-β-ocimene (0.7–11.3%) as major products (Table 3). The diterpene beyerene (0.2–9.1%) and benzoic acid (1.7–4.7%) were also relatively abundant. Cascade Range samples T.h. #1, T.h. #2, and T.h. #3, and Coastal Range sample T.h. #5 were similar in composition to the samples from Maple Ridge, British Columbia, Canada, previously reported by von Rudloff [56].
A hierarchical cluster analysis (HCA) was carried out to visualize the similarities between the T. heterophylla essential oil compositions (Figure 12). The HCA shows that the British Columbia samples and the Oregon samples #1–#3 and #5 form a relatively large cluster with >88% similarity. Oregon Coastal Range samples #4 and #6 are qualitatively similar to the large cluster, but different (with 66% similarity) in that sample #4 showed a lower myrcene concentration (only 7.0%), while sample #6 showed a relatively low β-pinene concentration (6.4%); both samples were also low in β-phellandrene (6.6% and 8.4%, respectively). Curiously, a sample collected in 2020 from a single tree growing in the Hoyt Arboretum near Portland, Oregon, was very different in composition with only 5.7% monoterpene hydrocarbons, including no observed α-pinene [58]. The concentration of α-terpineol (10.3%) was relatively high in the Hoyt Arboretum sample. It is not clear what factors may account for the dissimilarity between the Hoyt Arboretum sample and the other T. heterophylla samples. The Hoyt Arboretum sample was collected in September 2020, while the samples in this present study were collected in April 2023. However, von Rudloff sampled trees from Vancouver, British Columbia, in both March 1974, and October 1974, which showed no significant difference in the α-pinene concentrations (both 15.3%) or the α-terpineol concentrations (0.8% and 0.5%, respectively) [56].
In comparing the compositions of the samples from the Oregon Cascade and Coastal ranges, there are no significant differences between their major components (α-pinene, β-pinene, myrcene, α-phellandrene, limonene, β-phellandrene, (Z)-β-ocimene, benzoic acid, and beyerene) (Figure 13). This result is consistent with the previous study by von Rudloff [56], who found no significant differences in the compositions of trees located in the British Columbia Coastal Range and those of trees from the Rocky Mountains. The low level of genetic diversity can be explained by past vegetation history. That is, genetic diversity in T. heterophylla, as well as T. plicata, is likely to be diminished due to a population bottleneck during the last glacial maximum [67].
A PCA analysis of the T. heterophylla samples also was carried out and F1 and F2 explained a variability of 88.08%. The results observed corroborated the HCA analysis displaying a separation into four groups (Figure 14). The F1 samples showed positive correlations with samples rich in myrcene (6.818), β-phellandrene (5.459), α-pinene (5.347), β-pinene (2.342), and (Z)-β-ocimene (0.990), and negative correlations with thymyl methyl ether (−2.407), γ-cadinene (−2.280), terpinolene (−2.246), δ-cadinene (−2.207), α-cadinol (−2.120), α-terpineol (−2.078), benzoic acid (−1.868), τ-cadinol (−1.808), beyerene (−1.711), α-phellandrene (−1.612), and limonene (−0.620). On the other hand, F2 showed positive correlations with beyerene (2.804), α-pinene (1.087), and α-terpineol (1.072), but negative correlations with terpinolene (−1.086), α-phellandrene (−0.940), (Z)-β-ocimene (−0.895), γ-cadinene (−0.832), and benzoic acid (−0.796).

2.2. Enantiomeric Distribution

Enantioselective GC-MS analyses were carried out on the C. lawsoniana, T. plicata, and T. heterophylla foliar essential oils (Table 4, Table 5 and Table 6, respectively).
In C. lawsoniana (Table 4), (−)-α-thujene, (+)-cis-sabinene hydrate, (−)-bornyl acetate, and (+)-δ-cadinene were the only enantiomers detected. In addition, (+)-sabinene (enantiomeric excess, ee = 98.8 and 99.2%), (+)-limonene (ee = 99.6 and 99.8%), and (+)-trans-sabinene hydrate (ee = 89.9 and 92.6%) were the dominant enantiomers, while (+)-α-pinene (ee = 60.4 and 93.8%), (+)-terpinen-4-ol (ee = 45.0 and 34.4%), and (+)-α-terpineol (ee = 33.0 and 36.4%) were the major enantiomers in C. lawsoniana essential oil.
The exclusive enantiomers observed in T. plicata foliar essential oils (Table 5) include (−)-α-thujene, (+)-sabinene, (+)-β-pinene, (−)-α-thujone, and (+)-β-thujone. Although neither (−)-sabinene nor (−)-β-pinene were detected, a relatively large myrcene peak (RI = 1031) in the chiral GC-MS may have masked any (−)-sabinene or (−)-β-pinene, however. (+)-α-Pinene (95.5–99.0%), (+)-limonene (96.7–97.1%), (+)-cis-sabinene hydrate (96.8–97.6%), (+)-terpinen-4-ol (70.3–75.2%), and (+)-α-terpineol (60.6–64.5%) were also dominant enantiomers.
The enantioselective GC-MS of T. heterophylla essential oil (Table 6) showed α-pinene and linalool to be virtually racemic. The (+)-enantiomers were the predominant stereoisomers for sabinene, α-phellandrene, and (E)-nerolidol, while the (−)-enantiomers predominated for camphene, β-pinene, limonene, terpinen-4-ol, and α-terpineol; (−)-bornyl acetate, (−)-germacrene D, and (+)-δ-cadinene were the only enantiomers detected.
Based on this current work and previous studies of enantiomeric distributions of chiral monoterpenoids in conifer essential oils, there are some interesting trends (Table 7). (+)-α-Pinene is the dominant enantiomer in essential oils of the Cupressaceae, but, although it is not consistent, (−)-α-pinene generally predominates in the Pinaceae. Similar trends are seen for camphene, β-pinene, and limonene; the (−)-enantiomers are dominant in the Pinaceae while the (+)-enantiomers dominate the essential oils of the Cupressaceae. Although (+)-sabinene seems to be virtually exclusive in the Cupressaceae, the enantiomeric distribution is inconsistent in the Pinaceae. (−)-β-Phellandrene is clearly dominant in Pinaceae essential oils, but there are insufficient data to draw a conclusion regarding the Cupressaceae. (−)-Terpinen-4-ol and (−)-α-terpineol are slightly favored in the Pinaceae while the (+)-enantiomers are slightly favored in the Cupressaceae. There are not enough data regarding the enantiomeric distributions of linalool to draw a conclusion regarding the distribution trend.

3. Materials and Methods

3.1. Plant Material

The foliage of C. lawsoniana was collected from two separate trees (C. lawsoniana #1 and #2) on 15 April 2023, from the Van Duzer Forest, Oregon Coastal Range. The trees were identified in the field by W.N. Setzer using a field guide [16] and were verified through a comparison with samples from the New York Botanical Garden [74]. A voucher specimen (WNS-Cl-6886) has been deposited into the herbarium at the University of Alabama in Huntsville. The fresh foliage from each tree was frozen (−20 °C) and stored frozen until distillation. Foliage of T. plicata was collected from three different individual trees (T. plicata #1-#3) located near Mt. Hood Village, Oregon, on 14 April 2023 (Table 8). The trees were identified by W.N. Setzer [16,75] and a voucher specimen (WNS-Tp-6850) has been deposited into the herbarium at the University of Alabama in Huntsville. The fresh foliage was immediately frozen and stored frozen (−20 °C) until distillation. Tsuga heterophylla foliage from three individual trees (T. heterophylla #1-#3) was collected on 14 April 2023 near Mt. Hood Village, Oregon (Cascade Range) and from three individual trees (T. heterophylla #4-#6) on 16 April 2023 near Ross Lodge—Boger, Oregon (Coastal Range) (Table 8). The trees were identified in the field by W.N. Setzer using a field guide [16] and were verified through a comparison with botanical samples from the C. V. Starr Virtual Herbarium [76]. A voucher specimen, WNS-Th-6897, has been deposited into the herbarium at the University of Alabama in Huntsville. The foliage was frozen (−20 °C) and stored frozen until hydrodistillation.

3.2. Hydrodistillation

The fresh/frozen foliage of each sample was chopped and hydrodistilled for three hours using a Likens-Nickerson apparatus [77,78,79] with the continuous extraction of the distillate with dichloromethane (Table 8). Enough water to immerse the plant material was used for the hydrodistillation. The condenser was chilled (10–15 °C) using a refrigerated recirculating pump. Each plant sample was hydrodistilled once. The dichloromethane was evaporated using a stream of warm air.

3.3. Gas Chromatographic Analysis

The C. lawsoniana, T. plicata, and T. heterophylla foliar essential oils were analyzed via GC-MS, GC-FID, and chiral GC-MS as previously described [73]. The essential oil compositions were determined by comparing both MS fragmentation and RI values with those reported in the Adams [60], FFNSC3 [61], NIST20 [62], and Satyal [63] databases. The percent compositions were determined from raw peak areas (GC-FID) without standardization. Enantiomeric distributions were determined via the comparison of RI values with authentic samples (Sigma-Aldrich, Milwaukee, WI, USA), which were compiled in our in-house database.

3.4. Statistical Analyses

For the hierarchical cluster analysis (HCA) of C. lawsoniana, the eight essential oil compositions were treated as operational taxonomic units (OTUs), and the percentages of the 30 most abundant essential oil components (α-pinene, sabinene, myrcene, α-terpinene, limonene, γ-terpinene, camphor, terpinen-4-ol, citronellol, p-cymen-7-ol, methyl myrtenate, α-terpinyl acetate, 6-epi-β-cubebene, cis-cadina-1(6),4-diene, cis-muurola-4(14),5-diene, γ-amorphene, δ-cadinene, β-oplopenone, 1,10-di-epi-cubenol, τ-cadinol, α-cadinol, oplopanonyl acetate, beyerene, sandaracopimara-8(14),15-diene, manoyl oxide, abietatriene, cis-abienol, pimara-7,15-dien-3-one, trans-totarol, and trans-ferruginol) were used to describe the chemical associations between the C. lawsoniana essential oil samples. Pearson correlation was used to measure similarity, and the unweighted pair group method with arithmetic average (UPGMA) was used for cluster definition. The HCA analysis was carried out using XLSTAT v. 2018.1.1.62926 (Addinsoft, Paris, France). The HCA for T. plicata was carried out as described above using 15 essential oil compositions and the four most abundant essential oil components (sabinene, α-thujone, β-thujone, and terpinen-4-ol). The 16 major components of the T. heterophylla essential oils (α-pinene, β-pinene, myrcene, α-phellandrene, limonene, β-phellandrene, (Z)-β-ocimene, terpinolene, benzoic acid, α-terpineol, thymyl methyl ether, γ-cadinene, δ-cadinene, τ-cadinol, α-cadinol, and beyerene) were used to reveal the chemical associations between the 12 T. heterophylla essential oil samples as described above (Pearson correlation was used to measure similarity, and the UPGMA method was used for cluster definition).
Principal component analysis (PCA), type Pearson correlation, was carried out to verify the previous HCA analysis using the main essential oil components (as described above). The PCA analyses were carried out using XLSTAT v. 018.1.1.62926 (Addinsoft, Paris, France).
Student’s t-test [80,81] was used to evaluate the differences in the concentrations of sabinene, α-thujone, β-thujone, and terpinen-4-ol between the Oregon and the Idaho essential oil samples of Thuja plicata. Similarly, the t-test was used to compare the concentrations of α-pinene, β-pinene, myrcene, α-phellandrene, limonene, β-phellandrene, (Z)-β-ocimene, benzoic acid, and beyerene in the Coastal Range and Cascade Range essential oil samples of Tsuga heterophylla. Minitab® v. 19.2020.1 (Minitab, LLC, State College, PA, USA) was used to carry out the t-tests.

4. Conclusions

The present work revealed that wild-growing native Chamaecyparis lawsoniana essential oils show significant differences compared to the essential oils from trees cultivated in other geographical locations. On the other hand, essential oils of Thuja plicata are very similar, regardless of the collection site. Likewise, there are no significant differences between the Tsuga heterophylla essential oils from the Oregon Coastal Range and those from the Oregon Cascade Range. Both T. plicata and T. heterophylla likely have diminished genetic diversity, likely due to population bottlenecks during the last ice age. An examination of the distribution of monoterpenoid enantiomers indicates that the (+)-enantiomers seem to dominate α-pinene, camphene, sabinene, β-pinene, limonene, terpinen-4-ol, and α-terpineol in the Cuppressaceae, while the (−)-enantiomers seem to predominate for α-pinene, camphene, β-pinene, limonene, β-phellandrene, terpinen-4-ol, and α-terpineol in the Pinaceae. It would be interesting to see if these trends in enantiomeric distributions continue with additional research on the essential oils of gymnosperms.

Author Contributions

Conceptualization, W.N.S.; methodology, A.P., P.S. and J.K.R.d.S.; software, P.S.; validation, W.N.S. and J.K.R.d.S.; formal analysis, A.P., P.S., J.K.R.d.S. and W.N.S.; investigation, E.A., K.S., A.P., P.S., J.K.R.d.S. and W.N.S.; data curation, W.N.S.; writing—original draft preparation, W.N.S.; writing—review and editing, J.K.R.d.S. and W.N.S.; supervision, P.S. and W.N.S.; project administration, W.N.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding. The APC was funded by W.N.S.

Data Availability Statement

All data are available in the article.

Acknowledgments

This work was carried out as part of the activities of the Aromatic Plant Research Center (APRC, https://aromaticplant.org/). We thank Dewey Ankney for providing assistance in plant collection.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Chamaecyparis lawsoniana (A. Murray bis) Parl. (A): A photograph of its foliage, (B): A photograph of its bark (photographs taken by K. Swor at the time of sample collection).
Figure 1. Chamaecyparis lawsoniana (A. Murray bis) Parl. (A): A photograph of its foliage, (B): A photograph of its bark (photographs taken by K. Swor at the time of sample collection).
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Figure 2. Natural range of Chamaecyparis lawsoniana [25]. This image is in the public domain in the United States because it only contains materials that originally came from the United States Geological Survey, an agency of the United States Department of the Interior.
Figure 2. Natural range of Chamaecyparis lawsoniana [25]. This image is in the public domain in the United States because it only contains materials that originally came from the United States Geological Survey, an agency of the United States Department of the Interior.
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Figure 3. Photographs of Thuja plicata taken by K. Swor at the time of sample collection. (A): A photograph of its foliage. (B): A photograph of its bark.
Figure 3. Photographs of Thuja plicata taken by K. Swor at the time of sample collection. (A): A photograph of its foliage. (B): A photograph of its bark.
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Figure 4. The native range of Thuja plicata [25]. This image is in the public domain in the United States because it only contains materials that originally came from the United States Geological Survey, an agency of the United States Department of the Interior.
Figure 4. The native range of Thuja plicata [25]. This image is in the public domain in the United States because it only contains materials that originally came from the United States Geological Survey, an agency of the United States Department of the Interior.
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Figure 5. Tsuga heterophylla Sarg., Pinaceae (western hemlock). (A): Photograph of its foliage and cones. (B): Photograph of its bark. (C): Scan of the pressed foliage.
Figure 5. Tsuga heterophylla Sarg., Pinaceae (western hemlock). (A): Photograph of its foliage and cones. (B): Photograph of its bark. (C): Scan of the pressed foliage.
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Figure 6. The native range of Tsuga heterophylla [25]. This image is in the public domain in the United States because it only contains materials that originally came from the United States Geological Survey, an agency of the United States Department of the Interior.
Figure 6. The native range of Tsuga heterophylla [25]. This image is in the public domain in the United States because it only contains materials that originally came from the United States Geological Survey, an agency of the United States Department of the Interior.
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Figure 7. A dendrogram obtained via the hierarchical cluster analysis of Chamaecyparis lawsoniana essential oil compositions from different geographical locations: #1 and #2 (Oregon, this work), Greece [24], Japan [18], Spain [23], Belgium [19], Iran [22], and Egypt [21].
Figure 7. A dendrogram obtained via the hierarchical cluster analysis of Chamaecyparis lawsoniana essential oil compositions from different geographical locations: #1 and #2 (Oregon, this work), Greece [24], Japan [18], Spain [23], Belgium [19], Iran [22], and Egypt [21].
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Figure 8. A biplot based on the principal component analysis (PCA) of Chamaecyparis lawsoniana essential oil compositions from different geographical locations: #1 and #2 (Oregon, this work), Greece [24], Japan [18], Spain [23], Belgium [19], Iran [22], and Egypt [21].
Figure 8. A biplot based on the principal component analysis (PCA) of Chamaecyparis lawsoniana essential oil compositions from different geographical locations: #1 and #2 (Oregon, this work), Greece [24], Japan [18], Spain [23], Belgium [19], Iran [22], and Egypt [21].
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Figure 9. A dendrogram obtained via the hierarchical cluster analysis of Thuja plicata foliar essential oil compositions. von Rudloff [44], ID = samples from Idaho [49], OR = samples from Oregon (this work), Tsiri [46], Nikolic [48], Lis [47].
Figure 9. A dendrogram obtained via the hierarchical cluster analysis of Thuja plicata foliar essential oil compositions. von Rudloff [44], ID = samples from Idaho [49], OR = samples from Oregon (this work), Tsiri [46], Nikolic [48], Lis [47].
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Figure 10. A comparison of the percentages of the major components of Thuja plicata foliar essential oils from Oregon and from Idaho. t-test p-values: Sabinene, p = 0.746; α-Thujone, p = 0.241; β-Thujone, p = 0.057; Terpinen-4-ol, p = 0.372.
Figure 10. A comparison of the percentages of the major components of Thuja plicata foliar essential oils from Oregon and from Idaho. t-test p-values: Sabinene, p = 0.746; α-Thujone, p = 0.241; β-Thujone, p = 0.057; Terpinen-4-ol, p = 0.372.
Plants 13 01325 g010
Plants 13 01325 g011
Figure 11. A biplot based on the principal component analysis (PCA) of Thuja plicata foliar essential oil compositions. von Rudloff [44], ID = samples from Idaho [49], OR = samples from Oregon (this work), Tsiri [46], Nikolic [48], Lis [47].
Figure 11. A biplot based on the principal component analysis (PCA) of Thuja plicata foliar essential oil compositions. von Rudloff [44], ID = samples from Idaho [49], OR = samples from Oregon (this work), Tsiri [46], Nikolic [48], Lis [47].
Plants 13 01325 g011
Plants 13 01325 g012
Figure 12. A dendrogram obtained via the hierarchical cluster analysis (HCA) of the major foliar essential oil components of Tsuga heterophylla. #1–#6, samples from Oregon (this work); vR-1–vR-5, von Rudloff, 1975 [56]; 2020, sample from Oregon collected in 2020, Ankney et al., 2021 [58].
Figure 12. A dendrogram obtained via the hierarchical cluster analysis (HCA) of the major foliar essential oil components of Tsuga heterophylla. #1–#6, samples from Oregon (this work); vR-1–vR-5, von Rudloff, 1975 [56]; 2020, sample from Oregon collected in 2020, Ankney et al., 2021 [58].
Plants 13 01325 g012
Plants 13 01325 g013
Figure 13. A comparison of the mean percentages of the major components of the Tsuga heterophylla foliar essential oils from the Oregon Cascade Range and the Oregon Coastal Range. t-test p-values: α-Pinene, p = 0.590; β-Pinene, p = 0.956; Myrcene, p = 0.068; α-Phellandrene, p = 0.616; Limonene, p = 0.175; β-Phellandrene, p = 0.219; (Z)-β-Ocimene, p = 0.594; Benzoic acid, p = 0.295; Beyerene, p = 0.173.
Figure 13. A comparison of the mean percentages of the major components of the Tsuga heterophylla foliar essential oils from the Oregon Cascade Range and the Oregon Coastal Range. t-test p-values: α-Pinene, p = 0.590; β-Pinene, p = 0.956; Myrcene, p = 0.068; α-Phellandrene, p = 0.616; Limonene, p = 0.175; β-Phellandrene, p = 0.219; (Z)-β-Ocimene, p = 0.594; Benzoic acid, p = 0.295; Beyerene, p = 0.173.
Plants 13 01325 g013
Plants 13 01325 g014
Figure 14. A biplot based on the principal component analysis (PCA) of the Tsuga heterophylla foliar essential oil compositions. #1–#6, samples from Oregon (this work); vR-1–vR-5, von Rudloff, 1975 [56]; 2020, sample from Oregon collected in 2020, Ankney et al., 2021 [58].
Figure 14. A biplot based on the principal component analysis (PCA) of the Tsuga heterophylla foliar essential oil compositions. #1–#6, samples from Oregon (this work); vR-1–vR-5, von Rudloff, 1975 [56]; 2020, sample from Oregon collected in 2020, Ankney et al., 2021 [58].
Plants 13 01325 g014
Table 1. The foliar essential oil composition (%) of Chamaecyparis lawsoniana from the Oregon Coastal Range.
Table 1. The foliar essential oil composition (%) of Chamaecyparis lawsoniana from the Oregon Coastal Range.
RIcalcRIdbCompoundsC.l. #1C.l. #2
923923Tricyclenetrtr
925925α-Thujene0.50.8
933933α-Pinene0.42.3
947948α-Fenchenetrtr
949950Camphenetrtr
973972Sabinene7.06.5
977978β-Pinene tr0.1
978978Oct-1-en-3-ol0.10.2
989989Myrcene1.71.6
10071006α-Phellandrenetrtr
10171017α-Terpinene0.81.0
10251025p-Cymene0.20.6
102710262-Acetyl-3-methylfuran -tr
10301030Limonene27.422.0
10341031β-Phellandrene0.10.1
103410321,8-Cineoletrtr
10351034(Z)-β-Ocimenetrtr
10451045(E)-β-Ocimene0.10.1
10581057γ-Terpinene2.22.7
10701069cis-Sabinene hydrate0.30.3
10851086Terpinolene0.70.7
10891090Fenchonetrtr
10901091p-Cymenenetr0.1
11011099trans-Sabinene hydrate0.20.2
11071105α-Thujone0.10.1
11131113p-Mentha-1,3,8-trienetrtr
111611146-Camphenonetrtr
11181118β-Thujonetrtr
11221120trans-p-Mentha-2,8-dien-1-ol0.10.1
11251124cis-p-Menth-2-en-1-ol0.30.3
11331134cis-Limonene oxidetr-
113411352-Vinylanisoletrtr
11361137cis-p-Mentha-2,8-dien-1-ol0.10.1
11391139Nopinonetrtr
11401136trans-3-Caren-2-oltrtr
11421142trans-p-Menth-2-en-1-ol0.20.2
11461145trans-Verbenoltrtr
11471145Camphor0.10.1
11571157Sabina ketone-tr
11691169Umbellulonetrtr
11721170Borneoltrtr
11761176cis-Pinocamphonetrtr
117911792-Isopropenyl-5-methyl-4-hexenal0.10.3
11811180Terpinen-4-ol5.05.3
11841188Naphthalenetr-
11871186p-Cymen-8-ol0.10.2
11941196(4Z)-Decenal0.80.6
11951195α-Terpineol0.20.3
11961197(4E)-Decenal0.30.1
11971196cis-Piperitol0.10.1
12001201cis-Piperitenoltrtr
12061206Decanal0.20.1
12071208Verbenone-0.1
12091208trans-Piperitol0.10.1
12181218trans-Piperitenoltr-
12191218trans-Carveoltr-
12441246Carvone-tr
12561258(4Z)-Decen-1-ol0.50.5
125912569-Decyn-1-ol0.40.3
127212711-Decanoltrtr
12761276Methyl nerate0.20.1
12781277Phellandraltr-
12841285Bornyl acetate0.70.9
12901289Thymol-tr
12921293Undec-2-onetrtr
12951294Methyl myrtenate2.05.4
13181318(2E,4E)-Decadienal0.10.2
13191319Methyl geranatetr0.1
13241324(2E,4E)-Decadien-1-oltr0.1
13281327p-Mentha-1,4-dien-7-ol0.1tr
13311332trans-Carvyl acetatetr0.1
13461346α-Terpinyl acetate1.61.5
13571357cis-Carvyl acetatetrtr
13741376α-Ionoltr0.1
13771378Geranyl acetatetr0.1
13931398Cedr-8(15)-ene0.10.1
13951393Methyl perillate0.10.1
13981401Undec-10-enal0.1tr
14191417(E)-β-Caryophyllene0.1-
14211421(E)-α-Iononetrtr
14231423β-Cedrene-tr
14341433cis-Thujopsene0.31.0
14371437iso-Bazzanenetrtr
14411440Dihydro-β-ionol0.10.1
14451446cis-Muurola-3,5-diene0.80.8
14551454α-Humulene0.1tr
14591463cis-Cadina-1(6),4-diene0.20.2
14621463cis-Muurola-4(14),5-diene1.71.6
14641458Sabinyl isovalerate0.40.3
14741471β-Acoradiene0.1-
14821480Germacrene D0.1-
14921490γ-Amorphene0.20.2
14961496trans-Muurola-4(14),5-diene0.70.6
14971497α-Muurolenetrtr
15031503β-Himachalene0.10.5
15051506α-Chamigrenetrtr
15071505Cuparenetrtr
15131512γ-Cadinenetrtr
15151515Cubeboltrtr
15191518δ-Cadinene1.51.8
15201519trans-Calamenenetrtr
1531153110-epi-Cubenol0.90.7
15351535γ-Cuprenene0.10.2
15371538α-Cadinenetrtr
15471548cis-Muurola-5-en-4β-ol0.40.2
15581558cis-Muurola-5-en-4α-ol0.40.3
15711571(3Z)-Hexenyl benzoatetr0.1
15771576Spathulenoltr0.1
15821587Caryophyllene oxidetrtr
16041606β-Oplopenone0.81.2
16071599Widdrol0.10.1
16091606Cedrol0.41.4
161616141,10-di-epi-Cubenol1.11.3
16421640τ-Cadinol0.30.4
16441644τ-Muurololtr0.1
16471643Cubenol0.10.2
16551655α-Cadinol0.50.6
16621664ar-Turmeronetr0.1
16671668β-Turmerone0.10.1
16761673Acorenone A0.10.2
16841686epi-α-Bisabolol-0.2
17061708cis-Thujopsenol0.10.1
17131715trans-Thujopsenal0.10.5
17331735Oplopanone0.10.1
18741875Oplopanonyl acetate13.811.3
19371933Beyerene14.39.0
19431941Pimaradiene I-0.1
19631968Sandaracopimara-8(14),15-diene0.30.3
19911989Manoyl oxide0.20.5
19951997Kaur-15-ene0.20.1
20021998Luxuriadiene-2.7
2037---Atis-16-enetrtr
20432045Kaur-16-ene0.10.1
20502049Abietatriene0.10.1
2240---15-Beyeren-19-ol, methyl derivative0.40.4
22992302trans-Totarol0.50.4
Monoterpene hydrocarbons41.238.5
Oxygenated monoterpenoids12.116.1
Sesquiterpene hydrocarbons6.06.9
Oxygenated sesquiterpenoids19.319.3
Diterpenoids16.113.6
Benzenoid aromaticstr0.1
Others2.62.4
Total identified97.396.8
RIcalc = Retention index calculated with respect to a homologous series of n-alkanes on a ZB-5ms column [59]. RIdb = Reference retention index from the databases [60,61,62,63]. tr = trace (<0.05%).
Table 2. The foliar essential oil composition (percentages) of Thuja plicata from the Cascade Range, Oregon.
Table 2. The foliar essential oil composition (percentages) of Thuja plicata from the Cascade Range, Oregon.
RIcalcRIdbCompoundsT.p. #1T.p. #2T.p. #3
842842Ethyl 2-methyl butyrate0.10.10.1
924925α-Thujene0.10.20.2
932933α-Pinene0.40.60.7
946948α-Fenchenetrtrtr
948950Camphenetrtrtr
971971Sabinene1.13.52.6
976978β-Pinenetr0.10.1
978978Oct-1-en-3-oltrtrtr
987989Myrcene0.51.71.0
997997Ethyl hexanoatetrtrtr
10161017α-Terpinene0.30.70.5
10201022Ethyl 3-methylbut-3-enyl carbonatetrtrtr
10241025p-Cymene0.60.30.5
102610262-Acetyl-3-methylfuran trtrtr
10281030Limonene0.50.90.6
10301031β-Phellandrenetrtrtr
103410375-Methyl-(5E)-octen-2-one0.1tr0.1
10561057γ-Terpinene0.61.30.8
10701069cis-Sabinene hydrate0.30.40.2
10841086Terpinolene0.10.30.2
10901091p-Cymenenetrtrtr
10951093Ethyl sorbatetrtrtr
10981098Perillenetrtr0.1
11071105α-Thujone74.667.171.7
11201118β-Thujone8.07.89.3
11231122trans-p-Mentha-2,8-dien-1-oltrtrtr
11251124cis-p-Menth-2-en-1-ol0.20.30.2
11271127α-Campholenal0.1trtr
11391138trans-Sabinol0.1tr0.1
11411141trans-Pinocarveoltrtrtr
11421142trans-p-Menth-2-en-1-ol0.10.20.2
11451145trans-Verbenol0.10.10.1
11471145Camphortrtrtr
11521153neo-3-Thujanol0.10.10.1
11571157Sabina ketone0.20.10.2
11691168α-Phellandrene epoxidetr0.1tr
11691169Ethyl benzoatetr-tr
11711171p-Mentha-1,5-dien-8-oltrtrtr
11751176trans-Isopulegone0.10.10.1
11811180Terpinen-4-ol2.74.43.2
11871186p-Cymen-8-ol0.20.20.2
11921194p-Mentha-1,5-dien-7-ol0.1tr0.1
11951195α-Terpineol0.20.40.3
11981197Methyl chavicol (=Estragole)0.50.80.6
12071205Verbenone0.1tr0.1
12091208trans-Piperitol0.10.1tr
12191218trans-Carveol0.1tr0.1
12381238Carvacryl methyl ethertrtrtr
12421242Cuminaltrtr0.1
12441242Carvone0.1trtr
12461250Ethyl (2E)-octenoatetrtrtr
12491248Carvotanacetone0.1-0.1
12491249Linalyl acetate-0.1-
12601260trans-Sabinene hydrate acetate0.10.10.1
12681267neo-3-Thujyl acetate0.10.20.2
12821280Phellandraltr-tr
12831282Bornyl acetate0.10.10.1
12871286trans-Sabinyl acetatetr0.10.1
128912933-Thujanyl acetate0.10.10.1
12911290Menthyl acetate0.30.50.4
12921291p-Cymen-7-ol0.1-tr
12971300Carvacrol0.10.10.1
13151322Myrtenyl acetate0.10.10.1
13281327p-Mentha-1,4-dien-7-ol0.10.10.2
133513354-Terpinyl acetate0.10.10.1
13451346α-Terpinyl acetate0.20.40.2
13481349Citronellyl acetatetrtrtr
13571361Neryl acetate-tr-
13801378Geranyl acetate0.30.40.4
13971395Ethyl decanoatetrtrtr
14021403Methyl eugenoltrtrtr
14241426Cuminyl acetatetrtrtr
14471448(E)-Cinnamyl acetate--tr
14681467β-Acoradiene0.1--
14971495Tridecan-2-onetrtrtr
15201520δ-Cadinenetr0.1tr
15811578Furopelargone B0.10.1-
16041601Longiborneol (=Juniperol)--0.1
16051607β-Oplopenonetr0.1tr
16571655α-Cadinoltr0.20.1
16641664ar-Turmeronetrtrtr
16691668α-Turmerone0.1tr0.1
17341735Oplopanone0.10.10.1
18991896Rimuene1.00.80.3
19341931Beyerene0.90.60.4
19961997Kaur-15-enetrtrtr
2038---Atis-16-enetrtrtr
20522049Abietatrienetrtrtr
2243---15-Beyeren-19-ol 0.50.50.5
23012315trans-Totarol0.20.20.1
2319---15-Beyeren-19-ol acetate1.71.91.1
Monoterpene hydrocarbons4.29.67.1
Oxygenated monoterpenoids89.283.688.1
Sesquiterpene hydrocarbons0.10.1tr
Oxygenated sesquiterpenoids0.30.40.3
Diterpenoids4.44.12.4
Benzenoid aromatics0.50.80.6
Others0.10.10.2
Total identified98.798.798.7
RIcalc = Retention index calculated with respect to a homologous series of n-alkanes on a ZB-5ms column [59]. RIdb = Reference retention index from the databases [60,61,62,63]. tr = trace (<0.05%).
Table 3. The foliar essential oil compositions (percentages) of the Tsuga heterophylla from the Oregon Cascade Range and the Oregon Coastal Range.
Table 3. The foliar essential oil compositions (percentages) of the Tsuga heterophylla from the Oregon Cascade Range and the Oregon Coastal Range.
RIcalcRIdbCompoundsCascade RangeCoastal Range
T.h. #1T.h. #2T.h. #3T.h. #4T.h. #5T.h. #6
800797(3Z)-Hexenal0.10.10.10.10.10.2
802802Hexanaltr0.1trtr0.10.1
849849(2E)-Hexenal1.51.91.21.73.83.1
851853(3Z)-Hexenol0.20.30.20.30.50.4
922923Tricyclene0.10.10.10.10.10.1
925925α-Thujene0.10.10.10.10.1tr
933932α-Pinene17.118.414.415.315.427.2
947948α-Fenchenetrtrtrtrtrtr
949950Camphene0.30.30.20.30.20.3
972972Sabinene0.10.10.20.30.40.2
977978β-Pinene7.411.612.614.99.76.4
989989Myrcene27.619.424.37.017.713.7
10051005p-Mentha-1(7),8-diene---tr--
10071007α-Phellandrene2.21.40.9-1.66.0
10091008δ-3-Carene0.10.1trtrtr0.1
10171017α-Terpinene0.10.1tr-0.10.1
10241025p-Cymene1.20.71.31.51.11.8
10291030Limonene1.71.81.97.21.97.0
10311031β-Phellandrene11.619.319.26.616.68.4
103310321,8-Cineole---tr--
10351034(Z)-β-Ocimene11.34.35.20.78.06.6
10451045(E)-β-Ocimene0.40.20.1tr0.20.2
105010512,3,6-Trimethylhepta-1,5-diene---0.2--
10571057γ-Terpinene0.10.30.1-0.20.1
10651068Acetophenone---tr--
10701069cis-Sabinene hydrate---tr--
10851086Terpinolene0.40.60.4-0.60.6
10901091p-Cymenene----0.1-
109010906,7-Epoxymyrcene0.10.10.10.3-tr
10911091Rosefuran0.1tr0.10.1trtr
10981098Perillenetrtr0.10.2-tr
10991101Linalool0.20.10.1tr0.10.1
10991101α-Pinene oxide---0.6--
11071105α-Thujone-tr----
11191119endo-Fenchol0.1tr0.10.10.1tr
11241124cis-p-Menth-2-en-1-ol0.20.30.30.40.30.2
11261125α-Campholenaltrtr0.10.10.1tr
11271127(4E,6Z)-allo-Ocimene0.40.10.2-0.30.2
11291129(Z)-Myroxide---0.1--
11321132cis-Limonene oxide---0.1--
11371137trans-Limonene oxide---0.1--
11391141(E)-Myroxide---0.2--
11411141trans-Pinocarveol---0.30.10.1
11421142trans-p-Menth-2-en-1-ol0.20.20.20.40.20.2
11461146trans-Verbenol---0.2--
11551156Camphene hydrate---0.1--
11621164Pinocarvone---0.2--
11681167Benzoic acid1.92.84.71.72.22.0
11701169Rosefuran epoxide---0.1--
11721171p-Mentha-1,5-dien-8-ol----0.10.1
11801180Terpinen-4-ol0.30.50.30.40.60.3
11871185Cryptone0.40.40.92.20.50.2
11881188p-Cymen-8-ol---3.7--
11951195α-Terpineol1.51.01.31.51.61.3
11971196cis-Piperitol0.10.10.1-0.10.1
11971195Myrtenol---0.4--
12031202cis-Sabinol0.30.10.3-0.30.5
12071205Verbenone0.10.10.10.30.30.1
12091208trans-Piperitol0.10.10.10.10.1tr
122312274-Isopropylphenol---0.1--
12271227Citronellol0.1-----
12281229Thymyl methyl ether0.71.10.70.10.60.1
12441242Cuminal---0.5--
12461246Carvone---0.1--
12561254Piperitone---0.1--
12831282Bornyl acetate0.10.2tr0.20.1tr
12881287α-Terpinen-7-al---0.1--
12931291p-Cymen-7-ol---0.7--
13211320Methyl geranate---0.3-0.1
132413184-Hydroxycryptone---0.2--
134013393-Oxo-p-Menth-1-en-7-al---0.3--
13471348α-Cubebene-0.1----
13761375α-Copaene0.10.1tr0.20.1-
13781378Geranyl acetate0.10.10.10.10.10.1
14031405Siberenetr0.1----
14191417(E)-β-Caryophyllene0.10.10.1-0.10.1
14301430β-Copaenetrtr----
14521451(E)-β-Farnesenetr0.10.10.10.1tr
14551454α-Humulene0.10.1tr0.10.1tr
14751475γ-Muurolene0.10.20.10.30.1tr
14811480Germacrene D0.20.20.1-0.20.2
14891489β-Selinene0.20.20.10.60.20.1
14921490γ-Amorphenetr0.1----
14961497α-Selinene0.20.20.10.40.10.1
14981497α-Muurolene0.30.30.20.40.30.2
15121512γ-Cadinene0.50.70.31.40.30.2
15181518δ-Cadinene1.01.30.90.51.00.8
15211519trans-Calamenenetrtrtr0.1trtr
15361538α-Cadinenetrtrtr0.1trtr
15411541α-Calacorene---0.2--
15601560(E)-Nerolidol0.10.10.10.30.30.3
15761574Germacra-1(10),5-dien-4β-ol--0.1-0.10.1
16091611Humulene epoxide II---0.1--
161416141,10-di-epi-Cubenoltr0.1tr0.10.1tr
162716281-epi-Cubenol0.20.30.10.30.20.1
16411640τ-Cadinol0.50.70.61.10.80.6
16431644τ-Muurolol0.50.60.71.11.10.7
16461645α-Muurolol (=δ-Cadinol)0.20.20.20.40.40.3
16551655α-Cadinol0.70.81.91.82.72.1
16571660Selin-11-en-4α-ol0.10.10.10.30.20.1
16571663cis-Calamenen-10-ol---0.5--
16621660ar-Turmerone0.30.10.20.60.20.1
16641671trans-Calamenen-10-ol---0.2--
16671668α-Turmerone0.20.10.1-0.10.1
16781676(9Z,12E)-Tetradecadien-1-ol0.10.10.2-0.30.6
17001699β-Turmerone (=Curlone B)0.20.10.1-0.1tr
18661869Benzyl salicylatetr0.1tr0.1--
19321933Beyerene3.24.40.29.14.54.6
19941997Kaur-15-ene0.10.1-0.20.10.1
20492049Abietatriene0.10.10.51.5--
20512053Manool----0.30.2
20822086Abietadiene0.10.10.1---
Monoterpene hydrocarbons82.078.981.254.174.378.9
Oxygenated monoterpenoids4.54.25.014.85.13.3
Sesquiterpene hydrocarbons2.83.71.94.32.51.6
Oxygenated sesquiterpenoids3.03.14.36.96.24.4
Diterpenoids3.54.70.810.84.95.0
Benzenoid aromatics1.92.94.72.02.22.0
Others1.92.41.62.14.74.4
Total identified99.699.999.595.099.999.6
RIcalc = Retention index calculated with respect to a homologous series of n-alkanes on a ZB-5ms column [59]. RIdb = Reference retention index from the databases [60,61,62,63]. tr = trace (<0.05%).
Table 4. The enantiomeric distribution (percent of each enantiomer) of the chiral terpenoids in Chamaecyparis lawsoniana.
Table 4. The enantiomeric distribution (percent of each enantiomer) of the chiral terpenoids in Chamaecyparis lawsoniana.
CompoundsRIdbRIcalcC.l. #1C.l. #2
(+)-α-Thujene950n.o.0.00.0
(−)-α-Thujene 951951100.0100.0
(−)-α-Pinene97697719.83.1
(+)-α-Pinene98298180.296.9
(+)-Sabinene1021101899.699.4
(−)-Sabinene103010310.40.6
(+)-β-Pinene10271027100.0100.0
(−)-β-Pinene1031n.o.0.00.0
(−)-Limonene107310770.10.2
(+)-Limonene1081107999.999.8
(+)-cis-Sabinene hydrate11991199100.0100.0
(−)-cis-Sabinene hydrate1202n.o.0.00.0
(+)-trans-Sabinene hydrate1231123196.395.0
(−)-trans-Sabinene hydrate123512363.75.0
(+)-Terpinen-4-ol1297129367.272.5
(−)-Terpinen-4-ol1300129832.827.5
(−)-Bornyl acetate 13441346100.0100.0
(+)-Bornyl acetaten.a.n.o.0.00.0
(−)-α-Terpineol1347134831.833.5
(+)-α-Terpineol1356135668.266.5
(−)-δ-Cadinene1563n.o.0.00.0
(+)-δ-Cadinene 15761575100.0100.0
RIdb = Retention index from our in-house database based on commercially available compounds available from Sigma-Aldrich and augmented with our own data. RIcalc = Calculated retention index based on a series of n-alkanes on a Restek B-Dex 325 capillary column. n.o. = not observed. n.a. = no reference compound available.
Table 5. The enantiomeric distribution (percent of each enantiomer) of the chiral terpenoids in Thuja plicata.
Table 5. The enantiomeric distribution (percent of each enantiomer) of the chiral terpenoids in Thuja plicata.
CompoundsRIdbRIcalcT.p. #1T.p. #2T.p. #3
(+)-α-Thujene950n.o.0.00.00.0
(−)-α-Thujene951953100.0100.0100.0
(−)-α-Pinene9769794.51.21.0
(+)-α-Pinene98298395.598.899.0
(+)-Sabinene10211020100.0100.0100.0
(−)-Sabinene1030n.o.0.00.00.0
(+)-β-Pinene10271027100.0100.0100.0
(−)-β-Pinene1031n.o.0.00.00.0
(−)-Limonene107310752.92.93.3
(+)-Limonene1081108197.197.196.7
(+)-cis-Sabinene hydrate1199119797.297.696.8
(−)-cis-Sabinene hydrate120212002.82.43.2
(+)-α-Thujone1213n.o.0.00.00.0
(−)-α-Thujone12221221100.0100.0100.0
(+)-β-Thujone12301227100.0100.0100.0
(−)-β-Thujonen.a.n.o.0.00.00.0
(+)-Terpinen-4-ol1297129375.270.374.4
(−)-Terpinen-4-ol1300129824.829.725.6
(−)-α-Terpineol1347134735.539.437.8
(+)-α-Terpineol1356135564.560.662.2
RIdb = Retention index from our in-house database based on commercially available compounds available from Sigma-Aldrich and augmented with our own data. RIcalc = Calculated retention index based on a series of n-alkanes on a Restek B-Dex 325 capillary column. n.o. = not observed. n.a. = no reference compound available.
Table 6. The enantiomeric distribution (percent of each enantiomer) of the chiral terpenoid components in the foliar essential oil of the Tsuga heterophylla from Oregon.
Table 6. The enantiomeric distribution (percent of each enantiomer) of the chiral terpenoid components in the foliar essential oil of the Tsuga heterophylla from Oregon.
CompoundsRIdbRIcalcCascade RangeCoastal Range
T.h. #1T.h. #2T.h. #3T.h. #4T.h. #5T.h. #6
(−)-α-Pinene97697653.073.859.376.644.538.3
(+)-α-Pinene98298147.026.240.723.455.561.7
(−)-Camphene998100172.179.975.084.971.562.3
(+)-Camphene1005100627.920.125.015.128.537.7
(+)-Sabinene10211021100.0100.0100.059.6100.083.2
(−)-Sabinene103010280.00.00.040.40.016.8
(+)-β-Pinene102710272.21.92.13.63.58.3
(−)-β-Pinene1031103097.898.197.996.496.591.7
(−)-α-Phellandrene105010513.511.48.2n.o.7.11.7
(+)-α-Phellandrene1053105296.588.691.8n.o.92.998.3
(−)-Limonene1073107467.681.377.892.676.585.8
(+)-Limonene1081108132.418.722.27.423.514.2
(−)-β-Phellandrene1083108376.793.591.995.290.036.8
(+)-β-Phellandrene1089108823.36.68.14.810.063.2
(−)-Linalool1228122868.216.760.848.130.254.7
(+)-Linalool1231123131.883.339.251.969.845.3
(+)-Terpinen-4-ol1297129742.231.838.030.934.148.2
(−)-Terpinen-4-ol1300130057.868.262.069.165.951.8
(−)-Bornyl acetate 13441345100.0100.0100.0100.0100.0100.0
(+)-Bornyl acetaten.a.n.o.0.00.00.00.00.00.0
(−)-α-Terpineol1347134776.582.785.789.677.662.9
(+)-α-Terpineol1356135323.517.314.310.422.437.1
(+)-Germacrene D1519n.o.0.00.00.0n.o.0.00.0
(−)-Germacrene D 15221524100.0100.0100.0n.o.100.0100.0
(−)-δ-Cadinene1563n.o.0.00.00.00.00.00.0
(+)-δ-Cadinene 15761577100.0100.0100.0100.0100.0100.0
(−)-(E)-Nerolidol1677167732.117.320.215.637.047.4
(+)-(E)-Nerolidol 1680167967.982.779.884.463.052.6
RIdb = Retention index from our in-house database based on commercially available compounds available from Sigma-Aldrich and augmented with our own data. RIcalc = Calculated retention index based on a series of n-alkanes on a Restek B-Dex 325 capillary column. n.o. = not observed. n.a. = no reference compound available.
Table 7. The enantiomeric distribution (percent of each enantiomer) of the chiral terpenoids in members of the Pinaceae and Cupressaceae.
Table 7. The enantiomeric distribution (percent of each enantiomer) of the chiral terpenoids in members of the Pinaceae and Cupressaceae.
α-PineneCampheneSabineneβ-PineneLimoneneβ-PhellandreneLinaloolTerpinen-4-olα-Terpineol
Pinaceae(+)(−)(+)(−)(+)(−)(+)(−)(+)(−)(+)(−)(+)(−)(+)(−)(+)(−)Ref.
Abies concolor7228496n.o.n.o.1991189199712939611486[68]
Abies lasiocarpa var. lasiocarpa2476397n.o.n.o.199694010030703169n.on.o[49]
Abies procera43570100 an.o.n.o.2980100298n.o.n.o.4852892[58]
Picea engelmannii subsp. engelmannii3763793n.o.n.o.4965951189326844564753[49]
Picea pungens36647931000397496793267442584852[69]
Pinus contorta subsp. contorta2773n.o.n.o.n.o.n.o.01001387199n.o.n.o.53473565[70]
Pinus contorta subsp. latifolia13872179n.o.n.o.298128819920804456694[49]
Pinus contorta subsp. murrayana2080n.o.n.o.n.o.n.o.298010019901004060397[58]
Pinus edulis6436297118823973070199346637632476[71]
Pinus flexilis59529810003973367397n.o.n.o.4357991[70]
Pinus monophylla70304357n.o.n.o.3973169199n.o.n.o.34662674[71]
Pinus ponderosa var. ponderosa27732278n.o.n.o.29840601999913664397[70]
Pseudotsuga menziesii var. glauca1882298298298188239779334661783[49]
Tsuga heterophyllan.o.n.o.n.o.n.o.n.o.n.o.n.o.n.o.01000100n.o.n.o.30701387[58]
Tsuga heterophylla4258267492849620801981544637632179t.w.
Cupressaceae
Chamaecyparis lawsoniana8911n.on.o.9911000991n.o.n.o.n.o.n.o.70306733t.w.
Juniperus horizontalis811963371000100083173169613967335149[72]
Juniperus osteosperma99193710001000982n.on.on.o.n.o.67331000[73]
Juniperus scopulorum92852481000100090104753881253475446[72]
Thuja plicata8317n.o.n.o.10008515964n.on.on.o.n.o.74266832[49]
Thuja plicata982n.o.n.o.10001000973n.on.on.o.n.o.73276238t.w.
a Enantiomer misassigned in the original report. n.o. = not observed. t.w. = this work (mean values).
Table 8. The collection and hydrodistillation details for the Chamaecyparis lawsoniana, Thuja plicata, and Tsuga heterophylla foliar essential oils.
Table 8. The collection and hydrodistillation details for the Chamaecyparis lawsoniana, Thuja plicata, and Tsuga heterophylla foliar essential oils.
SampleDateCollection SiteMass
Foliage		Mass Essential OilYield, Color
C. lawsoniana #115-Apr-2345°2′16″ N, 123°48′29″ W,
116 m asl		82.74 g1.5694 g 1.897%,
pale yellow
C. lawsoniana #215-Apr-2345°2′19″ N, 123°48′30″ W,
117 m asl		158.78 g 3.6999 g 2.330%,
pale yellow
T. plicata #114-Apr-2345°20′58″ N, 121°59′39″ W,
362 m asl		81.66 g 0.6684 g 0.814%,
pale yellow
T. plicata #214-Apr-2345°20′58″ N, 121°59′46″ W,
359 m asl		91.83 g 0.6932 g 0.755%,
colorless
T. plicata #314-Apr-2345°20′58″ N, 121°59′51″ W,
359 m asl		54.91 g 0.5653 g 1.030%,
colorless
T. heterophylla #114-Apr-2345°20′58″ N, 121°59′40″ W,
362 m asl		70.39 g 3.7160 g 5.279%,
colorless
T. heterophylla #214-Apr-2345°20′58″ N, 121°59′44″ W,
360 m asl		62.83 g 3.9040 g 6.214%,
colorless
T. heterophylla #314-Apr-2345°20′59″ N, 121°59′51″ W,
359 m asl		50.53 g 3.1256 g 6.186%,
colorless
T. heterophylla #416-Apr-2345°2′15″ N, 123°48′29″ W,
114 m asl		78.89 g 4.3224 g 5.479%,
colorless
T. heterophylla #516-Apr-2345°2′17″ N, 123°48′30″ W,
117 m asl		95.21 g 5.9732 g 6.274%,
colorless
T. heterophylla #616-Apr-2345°2′18″ N, 123°48′30″ W,
117 m asl		61.30 g 4.7489 g7.747%,
colorless
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Ankney, E.; Swor, K.; Poudel, A.; Satyal, P.; da Silva, J.K.R.; Setzer, W.N. Chemical Compositions and Enantiomeric Distributions of Foliar Essential Oils of Chamaecyparis lawsoniana (A. Murray bis) Parl, Thuja plicata Donn ex D. Don, and Tsuga heterophylla Sarg. Plants 2024, 13, 1325. https://doi.org/10.3390/plants13101325

AMA Style

Ankney E, Swor K, Poudel A, Satyal P, da Silva JKR, Setzer WN. Chemical Compositions and Enantiomeric Distributions of Foliar Essential Oils of Chamaecyparis lawsoniana (A. Murray bis) Parl, Thuja plicata Donn ex D. Don, and Tsuga heterophylla Sarg. Plants. 2024; 13(10):1325. https://doi.org/10.3390/plants13101325

Chicago/Turabian Style

Ankney, Elizabeth, Kathy Swor, Ambika Poudel, Prabodh Satyal, Joyce Kelly R. da Silva, and William N. Setzer. 2024. "Chemical Compositions and Enantiomeric Distributions of Foliar Essential Oils of Chamaecyparis lawsoniana (A. Murray bis) Parl, Thuja plicata Donn ex D. Don, and Tsuga heterophylla Sarg." Plants 13, no. 10: 1325. https://doi.org/10.3390/plants13101325

APA Style

Ankney, E., Swor, K., Poudel, A., Satyal, P., da Silva, J. K. R., & Setzer, W. N. (2024). Chemical Compositions and Enantiomeric Distributions of Foliar Essential Oils of Chamaecyparis lawsoniana (A. Murray bis) Parl, Thuja plicata Donn ex D. Don, and Tsuga heterophylla Sarg. Plants, 13(10), 1325. https://doi.org/10.3390/plants13101325

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