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Article

Essential Oil Composition of Ten Species from Sect. Serpyllum of Genus Thymus Growing in Bulgaria

by
Antoaneta Trendafilova
1,*,
Milka Todorova
1,
Viktoria Ivanova
1,
Petar Zhelev
2 and
Ina Aneva
3
1
Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
2
Department of Dendrology, Faculty of Forestry, University of Forestry, 1797 Sofia, Bulgaria
3
Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
*
Author to whom correspondence should be addressed.
Diversity 2023, 15(6), 759; https://doi.org/10.3390/d15060759
Submission received: 16 May 2023 / Revised: 6 June 2023 / Accepted: 7 June 2023 / Published: 8 June 2023
(This article belongs to the Special Issue Chemistry and Biology of Medicinal and Aromatic Plants)
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Abstract

:
GC-MS/FID analysis of the essential oils of 10 Thymus species, belonging to Sect. Serpyllum, led to identification of 118 compounds accounting for 97.79–99.69% of the total oil. Thymus moesiacus, T. jankae, T. vandasii, T. longicaulis and T. sibthorpii were characterized by the presence of linalool (19.37–35.21%) as the major or dominant component, but differed significantly in the content of the other prominent components: linalyl acetate, geraniol, geranyl acetate, α-terpinyl acetate, myrcen-8-yl acetate, myrcen-8-ol, etc. α-Terpinyl acetate (66.79%), thymol (63.96%), carvacrol (42.65%) and germacrene D (42.15%) were the principal components of T. pulegioides, T. glabrescens, T. callieri and T. pannonicus, respectively. β-Myrcene (16.53%), cis-sabinene hydrate (13.58%), τ-cadinol (13.24%) and elemol (11.29%) determined the oil from T. thracicus as a mixed mono-/sesquiterpene chemotype. The obtained results revealed the existence of new chemotypes of T. moesiacus, T. thracicus, T. sibthorpii and T. longicaulis. The essential oil content of T. callieri and endemic T. vandasii is reported for the first time. The variations in the essential oils of different Thymus species from Sect. Serpyllum were examined by principal component analysis (PCA) and cluster analysis (CA).

1. Introduction

Essential oils are aromatic oily liquids derived from different plant parts (flowers, buds, seeds, leaves, twigs, bark) and represent complex mixtures of volatile constituents, including monoterpenes, sesquiterpenes and their oxygenated derivatives. They play a significant role in plant resistance against pests, herbivores, fungi and bacteria [1]. Essential oils have various applications in health, agriculture, cosmetic and food industries. The use of essential oils in traditional medicine has been practiced since ancient times in human history due to their wide range of biological properties such as antimicrobial, antiviral, antimutagenic, anticancer, antioxidant, anti-inflammatory, immunomodulatory and antiprotozoal activities [2]. Plants producing essential oils belong to various genera distributed to around 60 families, among which are the species of the genus Thymus (Lamiaceae).
Genus Thymus includes about 220 species distributed almost everywhere in Eurasia, as well as southern Greenland and Africa. The taxonomy of this genus is still challenging due to high population variability and chemical polymorphism [3]. Bulgarian flora is represented by 21 species belonging to two sections—Hyphodromi and Serpyllum [4]. Of them, six species are endemic to the Balkan Peninsula.
Recently, we have started a detailed study of the volatile compounds of Thymus species growing in Bulgaria. The investigation of five species belonging to sect. Hyphodromi has shown a considerable variation in the chemical composition of the species and the existence of new chemotypes [5]. Continuing our study, we focused on 10 species belonging to sect. Serpyllum. Thymus jankae Čelak., T. sibthorpii Benth., T. thracicus Velen. and T. vandasii Velen. are characterized by relatively limited distribution on the Balkan Peninsula and the Asian part of Turkey; T. callieri Borbás ex Velen. is spread out from the Balkans to Ukraine and Transcaucasia (Azerbaijan, Armenia and Georgia); while T. pannonicus All., T. longicaulis C. Presl, T. moesiacus Velen., T. pulegioides L. and T. glabrescens Willd. (or Benth., nom. Illeg) are widely distributed in Europe [6]. The literature survey on the volatile components of these species, summarized in Table S1 (Supplementary Material) [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73], revealed the existence of chemotypes of T. moesiacus, T. sibthorpii, T. jankae and T. thracicus and a high level of polymorphism with more than 10 chemotypes of T. pannonicus, T. glabrescens, T. longicaulis and T. pulegioides. It has been reported that different genetic and environmental factors may also influence the chemical composition of Thymus essential oils [3,74]. To our knowledge, the volatile constituents of T. vandasii and T. callieri have not been investigated yet. There are no data on the essential oil composition of the Bulgarian populations of these species except for two reports for T. moesiacus [39] and T. jankae [11]. Thus, the aim of this study was to characterize their volatile components, to get additional insights about their relationship in Sect. Serpyllum and to compare the results with the essential oil composition of these species from other origins reported so far in the literature.

2. Materials and Methods

2.1. Plant Material

Plant material was collected in July 2019 in the full flowering stage from the native populations in Bulgaria and air dried in the shade at room temperature. Voucher specimens have been deposited in the Herbarium of the Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences. The collection site and voucher specimens are given in Table 1.

2.2. Isolation of the Essential Oils

An amount of 5 grams of each sample were subjected to a micro hydrodistillation extraction in a Likens–Nickerson apparatus for 2.5 h using diethyl ether as a solvent [75]. The essential oil dissolved in diethyl ether was dried over anhydrous Na2SO4. After filtration, the solvent was removed under N2 flow, and the essential oil was stored at 4 °C before analysis. The yield of essential oil from the aerial parts of Thymus species is given in Table 1.

2.3. Gas Chromatography–Flame Ionization Detection/Mass Spectrometry (GC-FID/MSD)

Analyses were carried out with an Agilent 7890B gas chromatograph equipped with flame ionization detector and mass selective detector Agilent 5977A. HP-5MS capillary column (5%-phenyl)-methylpolysiloxane, 30 m × 0.25 mm; 0.25 μm film thickness) was used with a helium carrier gas at 1.2 mL/min. GC’s oven temperature was kept at 60 °C for 10 min and programmed to 200 °C at a rate of 3 °C/min, and then held at 200 °C for 10 min. The oils were analyzed with a split ratio of 10:1. The injector temperature was 270 °C. Temperatures of the MSD and the source were 230 and 150 °C, respectively. Mass spectra were taken at 70 eV, and the mass range was from m/z 35 to 450. Relative percentage amounts of the compounds were calculated from FID chromatograms.

2.4. Identification of Compounds

Relative retention indices (RRI) of the oil components were calculated using retention times of C8-C30 n-alkanes under the same chromatographic conditions. The individual components were identified by their MS, and RRI referring to known compounds from the literature [76,77], and also, by comparison with those of NIST 14 Library and home-made MS databases.

2.5. Statistical Analysis

Principal component analysis (PCA) and cluster analysis (CA) were performed using the PAST 4.0 software to determine the chemical variation and relationship between the species.

3. Results and Discussion

GC-MS/FID analysis of T. vandasii (TV), T. pannonicus (TPa), T. longicaulis (TL), T. moesiacus (TM), T. callieri (TC), T. pulegioides (TPu), T. glabrescens (TG), T. jankae (TJ), T. sibthorpii (TS) and T. thracicus (TT) essential oils led to the identification of 118 compounds accounting for 97.79–99.69% of the total oil. Of them, 115 compounds were unambiguously identified, and 3 were determined as a sesquiterpene hydrocarbon and 2 sesquiterpene alcohols based on their mass-spectral fragmentation (Table 2). The volatile compounds identified in the oils belong to six classes, namely monoterpene hydrocarbons (MH), oxygenated monoterpenes (MO), sesquiterpene hydrocarbons (SH), oxygenated sesquiterpenes (SO), aromatic compounds (AR) and others. It has been found that studied samples afforded specific chemical profiles with high variation in the type of compounds: MH (0.28–22.70%), MO (3.66–86.78%), SH (5.06–74.20%), SO (0.37–30.64%), AR (0.11–78.17%) and others (0.26–5.07%) (Figure 1). The essential oils differed significantly in the content of the individual components, too.
In the essential oil from T. moesiacus, 36 individual components were detected (Table 2). This oil was characterized by the highest amounts of O-containing monoterpenes (MO) −86.78%. The main MO in the oil were linalool, geraniol and geranyl acetate (35.21, 32.89 and 15.47%, respectively). Sesquiterpene hydrocarbons (SH) accounted 10.90% of the total oil, while all other types of compounds did not exceed 1%. Geraniol and geranyl acetate were found as the main components in two T. moesiacus essential oils from N. Macedonia [40], and linalool was the major component in another N. Macedonian sample [40] (Table S1). However, these samples were also rich in carvacrol (12.3–13.3%), while this component was detected in our sample only in traces. The study of essential oils of the species from Kosovo also showed the presence of linalool and geraniol in amounts between 6.9 and 13.8% along with carvacrol and thymol [8]. Linalool and thymol were the major components in T. moesiacus from Bosnia [39], while linalyl acetate (52.4%) was the most abundant component of T. moesiacus from another Bulgarian population [39]. Therefore, this essential oil could be characterized as a new linalool/geraniol/geranyl acetate chemotype.
The essential oil from T. vandasii contained 56 components (Table 2), and MO were the major class, followed by SO and SH. Linalool and linalyl acetate were the principal compounds (Figure 1). The content of linalyl acetate was twice higher than that of linalool (45.84% vs. 19.37%). β-Caryophyllene (4.51%) and elemol (4.92%) were the main sesquiterpenoids. The essential oil from T. vandasii was poor in MH (2.89%) and AR (0.11%). Therefore, T. vandasii belongs to linalyl acetate/linalool chemotype. This is the first report on the essential oil composition of T. vandasii. The results correlated with those found for the alpine populations of Thymus praecox Opiz ssp. polytrichus (Kern. ex Borb.) Ronn., emend. Jalas, a synonym of T. vandasii [6]. The study of the essential oils from 141 individual plants of Thymus praecox Opiz ssp. polytrichus revealed a high polymorphism with 12 different oil types, among which the most abundant chemotype was linalool/linalyl acetate type [78].
Oxygenated monoterpenes (MO) were also dominant in T. jankae essential oil, followed by SO and SH. The essential oil was poor in MH (4.55%) and AR (1.54%) (Figure 1). Among detected 51 components (Table 2), linalool (29.29%) and linalyl acetate (20.58%) were the major compounds, and τ-cadinol (6.07%) was the main sesquiterpenoid. The studied essential oil could be determined as linalool/linalyl acetate chemotype. Comparison of the chemical composition with the literature data for the Balkan populations of T. jankae (Table S1) showed similarities and differences. Thus, linalool seems to be a characteristic component of T. jankae as it was found in the essential oils from Bulgaria [11], Serbia [11], N. Macedonia [9], Kosovo [8] and Bosnia [10]. Linalyl acetate was reported in the essential oils from Bulgaria [11], Kosovo [8] and Bosnia [10] in amounts between 7.6 and 28.7%. The studied sample differed in the content of other components such as α-terpinyl acetate, geranial, (E)-caryophyllene, carvacrol and thymol. Thus, α-terpinyl acetate was the major component (20.1%) in another sample from Bulgaria [11], while its content in the studied sample was only 4.22%. T. jankae subsp. jankae from N. Macedonia [9] also contained a significant amount of α-terpinyl acetate (11.3%). Geranial was the second most abundant component (15.3–24.9%) in three varieties of T. jankae from N. Macedonia [9], while its content in our sample was only 1.75%. (E)-Caryophyllene (14.6%) and thymol (10.7%) were dominant compounds in the essential oil from Serbia [11], and carvacrol (13.8%) in the sample from Kosovo [8]. As can be seen from Table 2, the content of (E)-caryophyllene, thymol and carvacrol was 3.47, 1.22 and 0.31%, respectively. Finally, the studied population of T. jankae was very similar to that from Bosna with linalool and linalyl acetate as the main constituents [10].
The essential oil of T. longicaulis was also characterized by a high percentage of MO (Figure 1). Geraniol (25.28%), α-terpinyl acetate (17.46%), linalool (13.37%) and linalyl acetate (12.72%) were the main components (Table 2). This essential oil differed from the oils described above by the relatively high percentage of thymol (8.27%). Geraniol was found to be the main component in samples from Turkey [36], Greece [24,25] and Italy [26], α-terpinyl acetate-in samples from Serbia [28] and Turkey [29,36], linalool and linalyl acetate-in T. longicaulis ssp. longicaulis var. subisophyllus [38] and linalool and geraniol-in the sample from Kosovo [8]. Most of the studied T. longicaulis essential oils from Italian, Greek, Turkish and Croatian populations belonged to the thymol/p-cymene and carvacrol/p-cymene chemotypes (Table S1). Therefore, the studied essential oil could be described as a new geraniol/α-terpinyl acetate/linalool/linalyl acetate chemotype.
In the essential oil of T. pulegioides, 40 components were detected (Table 2). This oil was characterized by an extremely high content of α-terpinyl acetate (66.79%). In addition, geraniol (7.27%), thymol (6.70%), β-caryophyllene (2.48%) and α-terpineol (2.30%) were the compounds registered in amounts greater than 2%. This essential oil could be described as α-terpinyl acetate chemotype. It is worth mentioning that the European T. pulegioides individuals are predominantly phenolic (thymol/carvacrol) chemotypes, and individuals of α-terpinyl acetate chemotype are rare (Table S1). So far, α-terpinyl acetate was found to be the dominant component in essential oils of T. pulegioides growing wild in France at 1700 m a.s.l. (64.8–88.0%) [69] and in Lithuania (50.0–70.0%) in slopes with southern exposure [60,79]. Data in the literature showed only several species of genus Thymus containing α-terpinyl acetate in amounts over 45%, namely T. willkommii Ronniger (36–69%) [80], T. zygis (65–73%) [81], T. glabrescens Willd. (47.6%) [19], T. munbyanus subsp. ciliatus (43–82%) [82], T. longicaulis subsp. longicaulis (82.1%) [36] and T. pannonicus (35.7–48.8%) [46]. Recently, it has been found that α-terpinyl acetate essential oil from T. pulegioides possessed a high antimicrobial effect against fungi and dermatophytes and could be used as a potential source for developing preventive measures or/and drugs against mycosis [79].
In the oil of T. sibthorpii, 54 compounds were identified (Table 2). MO (63.80%) were the most abundant class of compounds followed by AR (16.71%), SH (9.70%) and MH (4.43%) (Figure 1). Among individual compounds, myrcen-8-yl acetate (22.03%), linalool (19.72%), myrcen-8-ol (14.71%) and thymol (10.67%) were detected in significant concentrations. While linalool and thymol are common components for Thymus species, the presence of myrcen-8-yl acetate and myrcen-8-ol is very rare in essential oils (Table S1). To our knowledge, myrcen-8-yl acetate was found in significant amounts in T. praecox Opiz ssp. arcticus (E. Durand) Jalas [83] and T. vulgaris L. [84], while myrcen-8-ol-in T. willkommii Ronn [80] and T. vulgaris L. [84]. The obtained data differed significantly from those for Greek and Turkish populations of the species for which geraniol/linalool/citronellyl acetate, geraniol/thymol/p-cymene, thymol/p-cymene and carvacrol/p-cymene chemotypes were described [38,70,71]. Therefore, the studied TS oil is a new myrcen-8-yl acetate/linalool/myrcen-8-ol chemotype.
The essential oil of T. pannonicus was the richest in components (63 compounds, Table 2). This sample was characterized by the highest content of SH (74.20%) and almost equal amounts of MH, MO and SO (5.07–6.76%). The main components, germacrene D (42.15%) and β-caryophyllene (12.28%), determined the oil as a germacrene D/β-caryophyllene chemotype. Similar amounts of germacrene D and β-caryophyllene (43.4 and 15.0%) were found in the essential oil of the plant growing on the Bakony Hills, Hungary [43]. Germacrene D was detected as a major component also in the essential oils of T. pannonicus from Serbia (36.9%) [50], Hungary (29.7%) [43] and Kosovo (18%) [14], but differed in the second most dominant compound. Although the sesquiterpenoids are not characteristic for species of genus Thymus, that type of compounds were detected in many T. pannonicus populations in significant amounts (Table S1) [8,14,43,48,50].
In the essential oil of T. thracicus, 54 compounds were identified (Table 2). This oil contained similar amounts of mono- and sesquiterpenoids (44.30 and 50.74%) (Figure 1). The main components were β-myrcene (16.53%), cis-sabinene hydrate (13.58%), τ-cadinol (13.24%) and elemol (11.29%), which determined the oil as β-myrcene/cis-sabinene hydrate/τ-cadinol/elemol chemotype. This oil differed significantly from those originating from Turkey [29,72] and from Thymus alsarensis Ronn. (syn. T. thracicus Velen.) from N. Macedonia [73], in which thymol/carvacrol and geraniol were the most abundant components. As can be seen from Table 2, these compounds were absent or were found in a negligible amount of T. thracicus essential oil. Therefore, this oil was a new chemotype.
Aromatic compounds (68.12%) were the prevailing class of compounds in the essential oil of T. callieri. The major components carvacrol (42.65%), thymol (13.38%) and γ-terpinene (12.04%) determined the oil is a carvacrol/thymol/γ-terpinene chemotype. Another aromatic compound p-cymene is also in significant concentration 7.17%. This is the first report on the essential oil composition of T. callieri from Bulgaria. Aromatic compounds were also the predominant class in the essential oil of T. roegneri (syn. of T. callieri) from Turkey with thymol (56.23%) and p-cymene (12.94%) as the main components [85]. Carvacrol was 8.59% and γ-terpinene was not detected in the Turkish sample.
The essential oil of T. glabrescens was the richest in aromatic compounds (78.17%). The oil contained equal amounts of MH and SH (7.49%), while MO and SO were 3.66 and 0.99%, respectively. Thymol (63.96%) was the main component, followed by p-cymene (7.17%) and γ-terpinene (4.48%), similar to some Hungarian [15,44], Serbian [11,20,21] and Romanian [18] oils. Generally, the presence of thymol and its precursors (p-cymene and γ-terpinene) was characteristic of T. glaberescens populations, although some variations in the main components from different locations (Table S1).
To demonstrate the relationship between the studied Thymus species from Section Serpyllum, the composition data were analyzed by principal component analysis (PCA) and cluster analysis (CA). The PCA conducted on the content of all constituents of each sample showed that the first 3 principal axes accounted for 65.77% of the total variations (Figure 2A,B). Considering the contributions to the loadings, PC 1 (25.91% of the total variations) accounted for positive contributions of thymol, α-terpinyl acetate, carvacrol, p-cymene, γ-terpinene, carvacrol methyl ether, borneol, α-terpinene, cis-sabinene hydrate, thymol methyl ether and eucalyptol and negative contributions of α-terpineol, 6-epi-shyobunol, germacrene D, τ-cadinol, β-caryophyllene, shyobunol, elemol, geranyl acetate, geraniol, linalyl acetate and linalool. PC 2 (24.73% of the total variations) was positively related to thymol, carvacrol, linalool, germacrene D, linalyl acetate, myrcen-8-yl acetate, p-cymene, γ-terpinene, β-myrcene, carvacrol methyl ether, myrcen-8-ol, β-caryophyllene, cis-sabinene hydrate, elemol and τ-cadinol and negatively related to 3-octanol acetate, sabinene, bornyl acetate, limonene, geranyl acetate, α-terpineol, geraniol and α-terpinyl acetate. As can be seen from Figure 2A, T. pulegioides was placed in the most isolated position (group I) due to the extremely high content of α-terpinyl acetate (66.79%). In contrast, the relatively high concentration of linalool, geraniol and their acetates grouped T. vandasii, T. jankae, T. moesiacus and T. longicaulis in group II. T. glabrescens and T. callieri formed group III and were discriminated from other species by the content of the aromatic compounds (thymol and carvacrol). The results do not agree with some recent taxonomic classifications [6], considering T. pannonicus as a subspecies of T. pulegioides. In the present study, the two taxa were clearly distinct (Figure 2), and in other studies they were even classified in different subsections [3].
Further, PC 3 (15.13% of the total variations) was positively related to linalool, geraniol, linalyl acetate, thymol, α-terpinyl acetate, myrcen-8-yl acetate and geranyl acetate and negatively related to β-myrcene, cis-sabinene hydrate, carvacrol, elemol, τ-cadinol, β-caryophyllene and germacrene D. The influence of these additional components allowed the re-grouping of T. sibthorpii, T. pannonicus and T. thracicus as follows: TS in group II due to the high percentage of linalool, myrcen-8-ol and myrcen-8-yl acetate, TPa in group IV with the highest content of sesquiterpenoids [germacrene D (42.15%) and β-caryophyllene (12.28%)] and TT in group V with almost equal amounts of β-myrcene (16.53%), cis-sabinene hydrate (13.58%), τ-cadinol (13.24%) and elemol (11.29%). Finally, group III was divided into 2 subgroups IIIa (TG) and IIIb (TC), depending on the dominating component–thymol and carvacrol. The cluster analysis (UPMGA, Euclidean distance) performed on the same data matrix (Figure 3) supported the differentiation of the samples obtained by the PCA analysis.
The cluster analysis (UPMGA, Euclidean distance) performed on the same data matrix (Figure 3) supported the differentiation of the samples obtained by the PCA analysis. As can be seen, six main chemotypes: α-terpinyl acetate, thymol, carvacrol, linalool, germacrene D/β-caryophyllene and β-myrcene/cis-sabinene hydrate/τ-cadinol/elemol were clearly distinguished. Inside the linalool chemotype, the contribution of the other main components resulted in the formation of additional chemotypes.

4. Conclusions

The obtained results showed considerable variation in the chemical composition of the species in this study: T. moesiacus, T. pulegioides, T. longicaulis, T. jankae, T. vandasii and T. sibthorpii were rich in monoterpenoids; T. callieri and T. glabrescens in aromatic compounds; T. pannonicus in sesquiterpenoids; while T. thracicus contained almost equal amounts of mono- and sesquiterpenoids. The chemical profile of T. moesiacus, T. thracicus, T. sibthorpii and T. longicaulis differed from that reported previously, and therefore, they formed new chemotypes. The essential oil content of endemic T. vandasii and T. callieri is reported for the first time. The described essential oil composition contributed to the phytochemistry of these species and confirmed the chemical polymorphism, a widespread phenomenon within the genus Thymus.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/d15060759/s1, Table S1: Literature survey of the main components in the essential oils of different Thymus species from sect. Serpyllum.

Author Contributions

Conceptualization, A.T. and I.A.; collection and identification of plant material, I.A. and P.Z.; preparation of essential oils, M.T. and V.I.; formal analysis, A.T.; methodology and investigation, A.T., M.T. and V.I.; writing—original draft preparation, A.T.; writing—review and editing, A.T., M.T., V.I., I.A. and P.Z.; visualization, A.T.; supervision and project administration, I.A. All authors have read and agreed to the published version of the manuscript.

Funding

The funding was provided by the Bulgarian National Science Fund, Project DN-16/3.

Institutional Review Board Statement

Not applicable in this study as it did not involve humans or animals.

Data Availability Statement

Not applicable.

Acknowledgments

The authors are thankful to the National Science Fund, Ministry of Education and Science, Bulgaria, for the financial support of Project DN16/3.

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Diversity 15 00759 g001 550
Figure 1. Main classes of compounds detected in Thymus essential oils (for abbreviation see Table 1).
Figure 1. Main classes of compounds detected in Thymus essential oils (for abbreviation see Table 1).
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Diversity 15 00759 g002 550
Figure 2. (A): PCA Biplot (PC1/PC2) and (B) PCA Biplot (PC1/PC3) for the whole set of data of the ten Thymus species from Sect. Serpyllum (for abbreviation see Table 1).
Figure 2. (A): PCA Biplot (PC1/PC2) and (B) PCA Biplot (PC1/PC3) for the whole set of data of the ten Thymus species from Sect. Serpyllum (for abbreviation see Table 1).
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Figure 3. Dendrogram obtained by cluster analysis (UPGMA, Euclidean distance) for the whole set of data of the 10 Thymus species from Sect. Serpyllum (for abbreviation see Table 1).
Figure 3. Dendrogram obtained by cluster analysis (UPGMA, Euclidean distance) for the whole set of data of the 10 Thymus species from Sect. Serpyllum (for abbreviation see Table 1).
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Table
Table 1. Collection site, voucher specimen and essential oil yield of Thymus species.
Table 1. Collection site, voucher specimen and essential oil yield of Thymus species.
SpeciesCodeCollection SiteGPS CoordinatesVoucher SpecimenYield
[%, w/w]
T. vandasiiTVSeven Rila lakes, Rila Mts.42°13′11.32″/
23°19′11.52″		SOM 14330.98
T. pannonicusTPaEastern Rhodopes Mts., road between Asenovgrad and Kardzhali41°39′36.08″/
25°20′30.32″		SOM 14290.39
T. longicaulisTLWestern Rhodopes Mts.42° 3′39.50″/
23°49′51.89″		SOM 14272.23
T. moesiacusTMZnepol region42°27′29.68″/
22°38′16.66″		SOM 14281.81
T. callieriTCStruma River Valley42° 0′11.58″/
23° 7′56.80″		SOM 14242.11
T. pulegioidesTPuVlahina Mts.41°59′18.88″/
22°55′39.02″		SOM 14301.18
T. glabrescensTGNorth-Eastern Bulgaria, near Dobrich43°31′10.37″/
27°45′16.11″		SOM 14251.69
T. jankaeTJSeven Rila lakes, Rila Mts.42°13′11.32″/
23°19′11.52″		SOM 14260.97
T. sibthorpiiTSDanube plain43°22′17.64″/
24°39′41.95″		SOM 14310.83
T. thracicusTTPirin Mts., Orelek peak41°32′51.80″/
23°37′19.28″		SOM 14320.09
Table
Table 2. Essential oil composition (%) from the aerial parts of Thymus species.
Table 2. Essential oil composition (%) from the aerial parts of Thymus species.
RRI *RRI **CompoundTV #TJ #TL #TM #TT #TC #TG #TS #TPu #TPa #*
923925α-Thujene--0.060.010.240.250.340.120.040.11
929929α-Pinene0.040.470.060.082.630.240.230.250.070.67
944946Camphene0.050.050.090.190.150.370.090.270.101.14
972970Sabinene0.01-0.09-0.380.01-0.060.370.09
973973β-Pinene0.01---1.360.110.110.230.200.18
9789801-Octen-3-ol0.230.450.150.151.040.510.900.860.111.63
9859863-Octanone--0.04--0.130.160.180.320.16
991991β-Myrcene1.091.500.38-16.530.650.841.990.120.27
9959943-Octanol--0.090.120.200.210.090.22-3.07
10151017α-Terpinene--0.11-0.231.350.990.210.170.15
10231022p-Cymene0.02-0.76-0.157.177.163.401.520.36
10281030Limonene0.391.420.48-0.360.310.300.641.393.09
10301032Eucalyptol-0.31-0.16-0.770.910.73-0.79
10371037cis-β-Ocimene0.260.220.15-------
10421045Benzene acetaldehyde0.05---0.14----0.30
10491049trans-β-Ocimene0.850.510.18-------
10561054γ-Terpinene0.050.070.69-0.8212.044.480.651.860.91
10651065cis-Sabinene hydrate0.060.110.08-13.581.141.040.450.060.19
10711070cis-Linalool oxide furanoid0.100.26-0.20---0.29--
108110801-Nonen-3-ol-----0.140.040.14-0.22
108510803-Nonanone----0.17-----
10871086trans-Linalool oxide furanoid-------0.33--
10871088Terpinolene0.150.310.16---0.11-0.240.07
10961098trans-Sabinene hydrate----1.010.300.22-0.090.12
10991099Linalool19.3729.2913.3735.21-0.120.3619.720.120.09
11001100Undecane----0.34-----
11021102Nonanal----0.29-----
11161111cis-2-p-Menthen-1-ol----0.18-----
112511233-Octanol acetate0.02-0.04---0.08-0.24-
11381140trans-2-p-Menthen-1-ol----0.11-----
11411145Camphor0.040.270.04-0.30----3.16
11431142trans-Verbenol-0.10--0.12-----
11481145Myrcenone-0.18--------
11631167Borneol0.100.180.401.29-4.590.681.010.471.37
11651167p-Mentha-1,5-dien-8-ol0.03---------
11751177Terpinen-4-ol0.110.130.120.062.300.450.370.260.130.30
11831183p-Cymen-8-ol-------0.14--
11881189α-Terpineol2.763.271.470.060.440.140.070.132.300.18
12171219Coumaran----0.26-----
12201221cis-Sabinene hydrate acetate-------0.43--
12261228Citronellol----0.49-----
12301226Myrcen-8-ol-------14.71--
12301230Nerol0.551.16-0.90----0.25-
12321235Thymol methyl ether--0.890.23-0.181.120.970.330.13
12421240Neral0.071.04-0.421.14-----
12431244Carvacrol methyl ether--0.670.040.343.934.340.790.150.01
12521250Thymoquinone-----0.160.670.25--
12541255Geraniol0.05-25.2832.890.20--2.757.27-
12561257Linalyl acetate45.8420.5812.72-------
12731270Geranial0.221.75--1.63-----
12841285Bornyl acetate0.05-0.270.06----0.430.09
12921291Thymol0.031.228.270.18-13.3863.9610.676.700.26
13001299Carvacrol0.010.310.040.07-42.650.410.190.220.08
130313056-Ethyl-3,4-dimethylphenol-------0.31--
13091309p-Vinylguaiacol----0.31-----
13351338δ-Elemene0.230.230.080.08--0.09--0.13
13491351α-Cubebene-----0.01---0.30
13491350α-Terpinyl acetate0.054.2217.460.06----66.79-
13511348Myrcen-8-yl acetate--------22.03--
13551357Eugenol------0.05--0.09
13651364Neryl acetate0.851.410.31-------
13711372Ylangene-----0.010.06--0.13
13731376α-Copaene-----0.010.110.07-0.49
13821384β-Bourbonene---0.500.080.160.080.24-0.82
13851382Geranyl acetate1.581.706.6415.470.10--0.960.48-
13891389β-Cubebene---------0.67
13901391β-Elemene0.100.08--0.38----1.82
14071409α-Gurjunene0.060.23--------
14191419β-Caryophyllene4.513.472.774.446.493.971.743.252.4812.28
14261432β-Copaene--0.030.12--0.120.13-2.25
14361440Aromandendrene------0.26---
144214422-Hydroxy-5-methoxyacetophenone-----0.170.16---
14411440Isogermacrene D--0.050.08------
14441440Cadina-3,5-diene-0.22--0.90-----
14511454Humulene0.270.270.210.283.800.28-0.530.13-
14541454Sesquisabinene---------2.52
14571457trans-β-Famesene-0.110.06------0.92
14581461Alloaromadendrene-0.52----0.15---
14611463cis-Muurola-4(15),5-diene-0.40--1.30-----
146014649-epi-β-Caryophyllene0.48---------
14751477γ-Muurolene-----0.520.470.190.39-
14811481Germacrene D0.220.240.512.180.890.26-1.07-42.15
14941493Epicubebol-----0.28---0.91
14931492Valencene------0.49---
14941495Bicyclogermacrene0.580.620.170.240.16-0.130.280.10-
14981500α-Muurolene0.240.19---0.140.060.08-1.01
15071509β-Bisabolene-0.382.802.81-0.782.253.421.886.15
151715176-epi-Shyobunol2.661.91--------
15131513γ-Cadinene-2.26--5.520.420.45--0.80
15181520trans-Calamenene----0.38-----
15211525Dihydroactinidiolide----0.14-----
15221522β-Cadinene-2.030.120.120.200.420.750.440.081.65
1526 C15H24 (MW 204)2.19---------
15401538trans-α-Bisabolene--0.350.06--0.29--0.10
15501549Elemol4.922.01--11.29--0.07-0.20
15541561Thymohydroquinone-----0.490.30---
15611562Geranyl butyrate--0.15-----0.11-
15781576Spathulenol0.20-0.070.09--0.280.23--
15741574Germacrene D-4-ol0.62---0.37----0.21
15821581Caryophyllene oxide0.39-0.190.610.410.470.300.610.290.21
16081604Geranyl isovalerate0.12-0.12-----0.08-
15921595Salvial-4(14)-en-1-one---------0.11
1607 C15H24O (MW 220)-------0.200.110.09
16161617Junenol---------0.09
16121614Di-epi-1,10-cubenol-0.72--1.78----0.11
16301627epi-Cubenol---------0.11
16301631γ-Eudesmol0.17---0.44-----
16341637Caryophylladienol-II--0.030.06---0.090.090.07
16401640τ-Cadinol-6.07--13.24--0.28-0.55
16431642τ-Muurolol0.22------0.10--
16451645δ-Cadinol0.04--------0.20
16491649β-Eudesmol0.170.07--0.50----0.08
16521653α-Eudesmol0.20--------0.98
16531653α-Cadinol0.340.84--1.01-0.30---
1663 C15H26O (MW 222)----1.25-----
16841680ent-Germacra-4(15),5,10(14)-trien-1β-ol--0.090.01--0.100.30-1.03
16861684α-Bisabolol-0.19--0.36-----
16891689Shyobunol3.782.76-----0.10-0.05
Total97.7998.3299.3699.5398.4199.6999.0798.0298.3198.48
Number of identified compounds56514936544250544063
* Relative retention index (RRI) determined relative to a homologous series of n-alkanes (C8-C25) on HP-5MS column; ** Relative retention index from the literature; # For abbreviation see Table 1.
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Trendafilova, A.; Todorova, M.; Ivanova, V.; Zhelev, P.; Aneva, I. Essential Oil Composition of Ten Species from Sect. Serpyllum of Genus Thymus Growing in Bulgaria. Diversity 2023, 15, 759. https://doi.org/10.3390/d15060759

AMA Style

Trendafilova A, Todorova M, Ivanova V, Zhelev P, Aneva I. Essential Oil Composition of Ten Species from Sect. Serpyllum of Genus Thymus Growing in Bulgaria. Diversity. 2023; 15(6):759. https://doi.org/10.3390/d15060759

Chicago/Turabian Style

Trendafilova, Antoaneta, Milka Todorova, Viktoria Ivanova, Petar Zhelev, and Ina Aneva. 2023. "Essential Oil Composition of Ten Species from Sect. Serpyllum of Genus Thymus Growing in Bulgaria" Diversity 15, no. 6: 759. https://doi.org/10.3390/d15060759

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