The alpha-terpenyl acetate chemotype of essential oil of Thymus pulegioides L

The composition of the essential oils of Thymus pulegioides L. plants growing wild in Vilnius district (Lithuania) with "ester", lemon and carvacrol (phenol) odours were collected in one location and investigated by GC, GC/MS and IR-spectroscopy. The essential oils with lemon and carvacrol odour belong to corresponding known citral-geraniol and carvacrol chemotypes. The essential oil of plants with "ester" odour containing 50-70% of alpha-terpenyl acetate belong to alpha-terpenyl acetate chemotype, which was not noticed earlier in Thymus pulegioides L. species.     

Essential oil composition and variability of Thymus lotocephalus and Thymusxmourae

The composition of the essential oils of four populations of Thymus lotocephalus G. López and R. Morales and one population of T.xmourae Paiva and Salgueiro, two endemic taxa from Portugal, was investigated mainly by GC and GC-MS. Txmourae is a natural hybrid between T. lotocephalus and T. mastichina (L.) L. subsp. donyanae R. Morales, which essential oil was analysed for the first time. In its oil, it was possible to find compounds of both parents, which could enable us to confirm its intermediate status between those two taxa. 1,8-Cineole and borneol were the main constituents in the essential oil of T.xmourae, whereas linalool, geranyl acetate and 1,8-cineol were the major ones in T. lotocephalus. Intermedeol was also an important constituent in the oils of both taxa. Nevertheless, the volatile oils of the four populations investigated of T. lotocephalus showed important differences among the main constituents. In order to study their infraspecific variability, the results obtained in the analysis of individual plants were submitted to a Principal Component and Chemometric Cluster Analyses. Five types of essential oils were found: linalool, 1,8-cineole, linalool/1,8-cineole, linalyl acetate/linalool and geranyl acetate.     

Antimicrobial activity of some Satureja essential oils

The genus Satureja is represented by fifteen species of which five are endemic and Satureja pilosa and S. icarica have recently been found as new records for Turkey. Aerial parts of the Satureja pilosa, S. icarica, S. boissieri and S. coerulea collected from different localities in Turkey were subjected to hydrodistillation to yield essential oils which were subsequently analysed by GC and GC/MS. The main constituents of the oils were identified, and both antibacterial and antifungal bioassays were applied. Carvacrol (59.2%, 44.8%, 42.1%) was the main component in the oils of S. icarica, S. boissieri and S. pilosa, respectively. The oil of S. coerulea contained beta-caryophyllene (10.6%) and caryophyllene oxide (8.0%) as main constituents.     

Chemotaxonomic study on Thymus villosus from Portugal

The composition of the essential oils of four populations of Thymus villosus subsp. lusitanicus (Boiss.) Coutinho from Portugal was investigated by GC and GC-MS. To study the chemical polymorphism the results obtained from GC analyses of the volatile oils from individual plants from four populations were submited to Principal Component and Cluster analyses. A comparision with the essential oil of T. villosus subsp. villosus, previously studied by us was done. Important differences with regard to the major constituents in these two taxa were found. Linalool, geranyl acetate, geraniol and terpinen-4-ol were the main components of the essential oils of T. villosus subsp. lusitanicus, whereas in the oil of T. villosus subsp. villosus p-cymene, myrcene and alpha-terpineol were the major ones. Although, both taxa showed chemical polymorphism, different types of essential oils were characterized in each one: linalool; linalool/ terpinen-4-ol/trans-sabinene hydrate; linalool/1,8-cineole; geranyl acetate/geraniol; geranyl acetate/geraniol/1,8-cineole in T. villosus subsp. lusitanicus and p-cymene/camphor/linalool; p-cymene/borneol; linalool/geraniol/geranyl acetate; alpha-terpineol/camphor/myrcene in T. villosus subsp. villosus. Thus, the two subspecies of T. villosus can be easely differenciated by the composition of their essential oils.     

Chemotaxonomic Analysis of the Aroma Compounds in Essential Oils of Two Different Ocimum basilicum L. Varieties from Iran

Hydrodistilled essential oils of 21 accessions of Ocimum basilicum L. belonging to two different varieties (var. purpurascens and var. dianatnejadii) from Iran were characterized by GC‐FID and GC/MS analyses. The oil yield was found to be between 0.6 and 1.1% (v/w). In total, 49 compounds, accounting for 96.6–99.7% of the oil compositions, were identified. Aromatic compounds, represented mainly by methyl chavicol (33.6–49.1%), and oxygenated monoterpenes, represented by linalool (14.4–39.3%), were the main components in all essential oils. Monoterpene hydrocarbons were present in the essential oils of all accessions of the purpurascens variety, whereas they were completely absent in those of the dianatnejadii variety, indicating that monoterpene hydrocarbons might be considered as marker constituents of the purpurascens variety. The chemotaxonomic value of the essential‐oil compositions was discussed according to the results of the cluster analysis (CA). The CA showed a clear separation of the O. basilicum var. purpurascens accessions and the O. basilicum var. dianatnejadii accessions, although the data showed no major chemotype variation between the studied varieties. Indeed, the CA revealed only one principal chemotype (methyl chavicol/linalool) for both varieties. In conclusion, GC/MS analyses in combination with CA showed to be a flexible and reliable method for the characterization of the chemical profiles of different varieties of Ocimum basilicum L.     

Essential oil production in shoot cultures versus field-grown plants of Thymus caespititius

Thymus caespititius Brot. is an important aromatic species, due to synthesis and production of essential oils for the pharmaceutical and food industries. In the present study, levels of essential oils from two chemotypes, including carvacrol/thymol (CT) and sabinene/carvacrol (SC), were evaluated in proliferating shoot cultures (6–12 subcultures following establishment) and compared to those from field-grown plants. The essential oils were isolated by hydrodistillation and analysed by gas chromatography (GC) and GC–mass spectrometry (GC–MS). Cultures grown under in vitro culture conditions, evaluated over six subcultures, were found to maintain stable composition of essential oils. For the CT chemotype, carvacrol (42 %) and thymol (23 %) were the main essential oil components detected in field-grown plants; in proliferating shoot cultures the levels detected attained 17–25 % in the case of carvacrol and 18–23 % in that of thymol, closely followed by carvacryl acetate (15–23 %) and thymyl acetate (11–15 %). For the SC chemotype, carvacrol (13–28 %), sabinene (18–45 %), and thymol (9–12 %) were the main essential oil components detected in both field-grown and proliferating shoot cultures. Our experiments showed that the essential oil composition in proliferating shoot cultures was not only stable, but also qualitatively similar to that of field-grown plants, notwithstanding minor quantitative differences.     

Essential‐Oil Composition of the Tunisian Endemic Cypress (Cupressus sempervirens L. var. numidica Trab.)

The essential oils isolated from leaves, wood, and cones of the Tunisian endemic cypress Cupressus sempervirens L. var. numidica Trab. collected from three natural populations were characterized by GC‐FID and GC/MS analyses. In the wood, leaf, and cone oils, 38, 35, and 26 constituents, representing 94.4, 97.8, and 98.5% of the total oil composition, respectively, were identified. Monoterpenes constituted the major fraction of the oils from all organs and for all populations. The oils were found to be of an α‐pinene (64.2%)/δ‐car‐3‐ene (11.1%) chemotype with considerable contents of α‐humulene (3.4%) in the leaf oil, cedrol (2.8%) in the wood oil, and sabinene (3.2%) in the cone oil, respectively. α‐Pinene, δ‐car‐3‐ene, limonene, carvacrol methyl ether, α‐humulene, and α‐amorphene were the main components that differentiated the oils of the three organs in the cypress of Makthar.     

The inflorescence and leaf essential oils of Tanacetum vulgare L. var. vulgare growing wild in Lithuania

Forty samples of inflorescences and leaves of wild Tanacetum vulgare L. var. vulgare were collected in 20 habitats from Lithuania. The essential oils were analyzed by GC and GC/MS. The 57 identified compounds in the oils made up 80.7–99.6%. According to the cluster analysis the volatile oils were divided into four groups with 1,8-cineole (23.6–46.3%, 11 oils), trans-thujone (35.7–78.4%, 6 samples), camphor (19.8–61.8%, 17 oils) and myrtenol (13.1–24.9%, 6 samples) as main constituents. The inflorescences and leaves of tansy plants formed the oils with the same dominating constituent in 15 of the 20 habitats investigated. The leaves in five localities produced oils of the 1,8-cineole chemotype, while the inflorescences biosynthesized oils of the camphor type in three habitats and of the myrtenol type in two habitats. Amounts of the 1,8-cineole in all leaf oils were greater than that in inflorescence oils of the plants from the same locality. An opposite correlation was determined for camphor, myrtenol, cis- and trans-thujone. The myrtenol chemotype was not noticed earlier in the essential oils of T. vulgare.     

Antimicrobial activity of essential oils isolated from Portuguese endemic species of Thymus

AIMS: Thymus species are wild species mostly found in the arid lands of Portugal. Possible antimicrobial properties of Thymus essential oils have been investigated. The chemical composition of the essential oils and the antimicrobial activity of Thymus mastichina (L) L. subsp. mastichina, T. camphoratus and T. lotocephalus from different regions of Portugal were analysed. METHODS AND RESULTS: Hydrodistillation was used to isolate the essential oils and the chemical analyses were performed by gas chromatography (GC) and GC coupled to mass spectrometry. The antimicrobial activity was tested by the disc agar diffusion technique against Candida albicans, Escherichia coli, Listeria monocytogenes, Proteus mirabilis, Salmonella spp. and Staphylococcus aureus. Pure linalool, 1,8-cineole and a mixture (1 : 1) of these compounds were included. Linalool, 1,8-cineole or linalool/1,8-cineole and linalool/1,8-cineole/linalyl acetate were the major components of the essential oils, depending on the species or sampling place. The essential oils isolated from the Thymus species studied demonstrated antimicrobial activity but the micro-organisms tested had significantly different sensitivities. CONCLUSIONS: The antimicrobial activity of essential oils may be related to more than one component. SIGNIFICANCE AND IMPACT OF THE STUDY: Portuguese endemic species of Thymus can be used for essential oil production for food spoilage control, cosmetics and pharmaceutical use. Further studies will be required to elucidate the cell targets of the essential oil components.     

Chemical diversity of volatiles of Teucrium orientale L. var. orientale, var. puberulens, and var. glabrescens determined by simultaneous GC-FID and GC/MS techniques

In the present work, three varieties of Teucrium orientale, var. orientale, var. puberulens, and var. glabrescens, were collected and investigated for chemical composition of the oils. Subsequent gas chromatography (GC-FID) and gas chromatography coupled to mass spectrometry (GC/MS) revealed high abundance of sesquiterpenes in the essential oils analyzed. All the oils contained β-caryophyllene (22.6, 8.5, and 6.3%, resp.) and hexadecanoic acid (7.9, 12.8, and 13.1%). Germacrene D (24.6 and 33.4%) and bicyclogermacrene (6.7 and 8.5%) were found to be the main constituents of var. orientale and var. puberulens, respectively. The high percentages of β-cubebene (26.9%), α-cubebene (9.0%), and α-copaene (7.2%) established the diversity of var. glabrescens. The qualitative difference between the essential oils allowed the differentiation between the varieties in agreement with the morphological observations described in Flora of Turkey for each variety studied. In addition, a cluster analysis of twelve Teucrium taxa based on the essential-oil composition has been carried out. Hovewer, the analysis did not clearly reflect the infrageneric classification of the genus, it largely confirmed the relationships between the infraspecific taxa of Teucrium orientale and T. chamaedrys.     

Geographical and environment-related variations of essential oils in isolated populations of Thymus richardii Pers. in the Mediterranean basin

Composition of essential oils of different populations of Thymus richardii grex of six localities from Bosnia-Herzegovina (Konjic, Borci), Spain (Majorca, Ibiza, Valencia) and Italy (Marettimo, Sicily) were determined by GC/FID and GC/MS. The main constituents in most of the samples were aromatic monoterpenes corresponding to non-phenolic cyclic compounds (p-cymene, γ-terpinene). The highest monoterpene concentrations were found in the Bosnian samples (70%), and the lowest in samples from the Balearic Islands (<30%; Ibiza and Majorca). Sesquiterpenes were the major component (average > 50%) in samples from Majorca with β-bisabolene (>40%) being the principal constituent. Discriminant analysis (LDA) shows the differentiation of two chemotypes: A (phenol chemotype), with p-cymene and γ-terpinene as characteristic compounds and B, with β-bisabolene and carvacrol, as major and significative compounds. The occurrence of the chemotypes was related to summer positive precipitation and to deep of soils.     

In-vitro antimicrobial activity and chemical composition of Sardinian Thymus essential oils

Essential oils and their components are becoming increasingly popular as naturally occurring antimicrobial agents. In this work the chemical composition and the antimicrobial properties of Thymus essential oils and of their main components were determined. Three essential oils obtained from different species of Thymus growing wild in Sardinia and a commercial sample of Thymus capitatus oil were analysed. The essential oil components were identified by GC/MS analysis. The antimicrobial activity of the oils and components was determined against a panel of standard reference strains and multiple strains of food-derived spoilage and pathogenic bacteria, using a broth microdilution method. The GC/MS analysis showed that the major constituents of the oils were monoterpene hydrocarbons and phenolic monoterpenes, but the concentration of these compounds varied greatly among the oils examined. The results of the antimicrobial assay showed that essential oils extracted from Sardinian Thymus species have an antimicrobial activity comparable to the one observed in other thyme oils. It seems also confirmed that the antimicrobial properties of thyme essential oils are mainly related to their high phenolic content. Among the single compounds tested carvacrol and thymol turned out to be the most efficient against both reference strains and food-derived bacteria. The results of this study confirmed the possibility of using thyme essential oils or some of their components in food systems to prevent the growth of foodborne bacteria and extend the shelf-life of processed foods.     

Essential oil variability of Thymus hyemalis growing wild in Southeastern Spain

Essential oils obtained by steam-distillation of individual samples of Thymus hyemalis were examined for variability in their volatile components by means of gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The thymol chemotype is widespread and is found in most of the vegetal formations where Thymus hyemalis is predominant and does not interact with other species. The carvacrol chemotype is found in isolated individual plants among those containing thymol. Although the chemotypes are usually mutually exclusive, the two phenols occasionally found with similar quantities in the same plant. The linalool chemotype has not previously been described for Thymus hyemalis. Other nonphenolic compounds (1,8-cineole, borneol, α-pinene) are present in low to medium percentages that reflect localized interactions with other species of thyme (Thymus vulgaris, Thymus baeticus) that sometimes produce hybridized or introgressive, morphologically distinguishable individuals.This chemical variability is analyzed by Principal Component Analysis (PCA) and Cluster Analysis (CA), a closely-related phenolic group of samples being revealed separated from less well represented non-phenolic chemotypes or mixed chemotypes. Multidimensional Scaling Analysis (MDS) based on percentage concentration was used to show the relationships between the most important components of the essential oil, the opposite orientation of vectors that represent phenolic compounds (and their precursors) and linalool, being of note. The data set presents positive correlation between camphor and altitude.     

Constituents of the essential oil of a new chemotype of Elsholtzia strobilifera Benth.

The composition of the essential oil from a new chemotype of Elsholtzia strobilifera Benth. collected from sub-alpine region of central Himalaya, India, has been investigated by Gas Chromatography and Gas Chromatography–Mass Spectrometry. The GC of the oil revealed the presence of more than 50 constituents, of which neral (18.3%) and geranial (29.9%) were found to be the major compounds and an absence of monoterpene hydrocarbons. Acylfuran derivatives, the specific chemical markers of the essential oils from the genus Elsholtzia were not detected.     

Chemical Composition and Antifungal Activity of the Essential Oils of Lavandula pedunculata (Miller) Cav.

The chemical composition and antifungal activity of the essential oils of Lavandula pedunculata (Miller ) Cav. , harvested in North and Central Portugal, were investigated. The essential oils were isolated by hydrodistillation and analyzed by GC and GC/MS. The minimal‐inhibitory concentration (MIC) and the minimal‐lethal concentration (MLC) of the essential oils and of their major constituents were used to evaluate the antifungal activity against different strains of fungi involved in candidosis, dematophytosis, and aspergillosis. The oils were characterized by a high percentage of oxygenated monoterpenes, the main compounds being 1,8‐cineole (2.4–55.5%), fenchone (1.3–59.7%), and camphor (3.6–48.0%). Statistical analysis differentiated the essential oils into two main types, one characterized by the predominance of fenchone and the other one by the predominance of 1,8‐cineole. Within the 1,8‐cineole chemotype, two subgroups were well‐defined taking into account the percentages of camphor. A significant antifungal activity of the oils was found against dermatophyte strains. The essential oil with the highest content of camphor was the most active with MIC and MLC values ranging from 0.32–0.64 μl/ml.     

Variability in essential-oil composition of Piper marginatum sensu lato

This paper contains data on the chemical composition of the essential oils of 22 leaf samples of Piper marginatum Jacq. collected in different areas and ecosystems of the brazilian Amazon, as well as an overview of the available literature. The species presents a large synonymy based on their different leaf characteristics and distinct scents where some of them smell like anise or very close compounds. By GC, GC/MS, and cluster analysis, we identified seven chemotypes for the leaf oils. The main components found in chemotype I were safrole (1) and 3,4-(methylenedioxy)propiophenone (2). The chemotype II was dominated by 3,4-(methylenedioxy)propiophenone (2) and p-mentha-1(7),8-diene (10). The major compounds identified in chemotype III were 3,4-(methylenedioxy)propiophenone (2), myristicin (3), (E)-beta-ocimene (11), and gamma-terpinene (12). In the chemotype IV, the principal constituents were beta-caryophyllene (13), alpha-copaene (14), and 3,4-(methylenedioxy)propiophenone (2). The chemotype V was dominated by (E)-isoosmorhizole (6), (E)-anethole (8), and isoosmorhizole (7). The main compounds found in the chemotype VI were 2-methoxy-4,5-(methylenedioxy)propiophenone (4), methoxy-4,5-(methylenedioxy)propiophenone isomer 5, and (E)-isoosmorhizole (6). The major constituents in chemotype VII were beta-caryophyllene (13), bicyclogermacrene (15), and (E)-asarone (9).     

Essential oil polymorphism of Thymus praecox subsp. arcticus on the British Isles

The essential oils of 732 individual plants of Thymus praecox Opiz subsp. arcticus (E. Durand) Jalas (syn. T. drucei Ronn.) collected in Scotland, Ireland, and in the south of England have been analysed by gas chromatography (GC) and mass spectrometry (GC–MS) in order to elucidate the chemical character of this subspecies on the British Isles. In total, 69 components were identified, most of them monoterpenoids and sesquiterpenoids with hedycaryol, linalyl acetate, linalool, the germacradienols, trans-nerolidol, T-cadinol, and β-caryophyllene being the most important compounds. The analysis of the quantitative essential oil data by means of neural networks revealed that T. praecox subsp. arcticus growing in Britain is highly polymorphous. There were 17 chemotypes with the hedycaryol chemotype as the most frequent (24% of the plants), followed by the linalool/linalyl acetate chemotype (22% of the plants) and germacra-1(10),4-dien-6-ol chemotype (18% of the plants). It seems that each part of the British Isles has its special chemotype pattern with 13 chemotypes in Scotland, 11 in Ireland, and 17 in the south of England. An overview of the North Atlantic region of Europe revealed that the polymorphism of T. praecox subsp. arcticus in the essential oil is more distinctive in the southern than in the northern regions, with only 2, 5, and 1 chemotypes in Greenland, Iceland, and Norway, respectively.     

Circadian and seasonal study of the cinnamate chemotype from Lippia origanoides Kunth

The leaves of Lippia origanoides Kunth are used in culinary as flavoring regional dishes and remedy for gastrointestinal and respiratory diseases in the Amazon region. The circadian and seasonal study of its essential oil was characterized by GC and GC–MS analysis. The oil components were grouped into monoterpenes, sesquiterpenes and phenylpropanoids, during the dry and rainy season. The main constituents were (E)-methyl cinnamate, (E)-nerolidol, p-cymene, 1,8-cineole, carvacrol, α-pinene, (E)-caryophyllene and γ-terpinene, with great variation throughout the year. In this work, we are reporting the occurrence of a new chemotype for L. origanoides, characterized by an essential oil rich in (E)-methyl cinnamate and (E)-nerolidol, with fruity-woody odor, reminiscent of cinnamon, strawberry and wood. The oil yield varied from 1.7% to 4.6%, which is considered a significant value for the production of essential oils on an industrial scale. This new chemotype may have ecological, chemosystematics and taxonomic significance in the management and economic utilization of the species.     

Chemotaxonomy of Serbian Teucrium species inferred from essential oil chemical composition: the case of Teucrium scordium L. ssp. scordioides

The volatile constituents of Teucrium scordium L. ssp. scordioides, T. polium, and T. montanum, obtained by hydrodistillation, were investigated by GC-FID and GC/MS analyses. A total of 296 constituents were identified, representing 89.8-98.4% of the oil compositions. The oils of T. polium and T. montanum consisted mainly of sesquiterpenes (64.3 and 72.7%, resp.), with germacrene D (4; 31.0%) and δ-cadinene (10; 8.1%) as the main constituents, respectively. In contrast, the monoterpene menthofuran (1; 11.9%) predominated in the oil of T. scordium ssp. scordioides, and this clearly distinguished this species from the other Teucrium taxa investigated up to date. The chemistry of the volatiles of eight Teucrium taxa from Serbia and Montenegro were compared using multivariate statistical analysis, and this provided chemotaxonomically important conclusions.     

A chemometric interpopulation study of the essential oils of Cistus creticus L. growing in Crete (Greece)

The chemical composition of the essential oils of twenty-five populations of Cistus creticus subsp. creticus L. from the island of Crete (Greece) and their interpopulation variability were analysed in detail by GC-MS. 142 compounds were identified representing an average of 56.8-89.8% of the oil composition. The components are represented here by homologous series of monoterpenes, oxygenated monoterpenes, sesquiterpenes, oxygenated sesquiterpenes, diterpenes, labdane diterpenes, aldehydes, alkanes, esters, fatty acids, ketones, and others. Labdane diterpenes were detected and identified in the essential oils and have been found in high percentage composition. The results from the chemical analysis of the essential oils were submitted to chemometric cluster analysis in order to detect some pattern distribution and to identify which constituents can differentiate the groups of individuals. Two main chemotypes (clusters) were well differentiated; the first deals with eight populations of West Crete and the second with the rest of the populations. Cluster analysis based on labdane type diterpenes patterns, proved to be the best chemotype for the examined populations among the other chemical groups.