Essential oil composition and preliminary molecular study of four Hungarian Thymus species

Chemical and genetic differences of twenty taxa belonging to four Thymus species were studied in order to determine whether molecular characters and essential oil components could be used as taxonomic markers and to examine the correlation between them. Plant samples, representing different taxa and geographic regions, were collected from experimentally grown populations. Essential oil samples were analysed by GC/MS and cluster analysis of volatile composition resulted in segregation of thymol chemotypes from sesquiterpenic ones. Thymol was characteristic for all the populations of Thymus glabrescens and T. pannonicus as well as for certain taxa belonging to T. praecox and T. pulegioides. Sesquiterpenes occurred in only two taxa of T. glabrescens, in each sample of T. praecox and in three taxa of T. pulegioides. Plant samples were analysed by random amplified polymorphic DNA (RAPD). The obtained dendrogram revealed high gene diversity. The 13 primers resulted 114 polymorphic RAPD bands, and the average percentage of polymorphism was 80.8%. The RAPD dendogram showed separation neither at interspecific nor at interpopulational levels. Therefore, further specific molecular studies involving more taxa are suggested. Partial correlation have been found between molecular and chemical assessments.     

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.     

Variation of Essential Oil Content and Composition,Phenolics, and Yield Related Traits Using Different Pollination Systems in Populations of Thymus Species

The production of self-pollinated plants could be important for improving medicinal plants secondary metabolites. In this study, 11 Thymus populations from eight species were evaluated to determine the effect of self and open pollination on agro-morphological characteristics, total phenolic content (TPC), essential oil (EO) content, and EO components. Inbreeding led to some positive effects of above mentioned traits in most of the studied populations. Total phenolic content ranged from 7.07 to 52.69 mg tannic acid equivalents (TAE) g⁻¹ dry weight (DW) in open pollinated derived populations, while it varied from 1.2 to 55.03 mg TAE g⁻¹ DW in self-pollinated ones. Under open and self-pollination condition, the highest EO content was obtained in T. trautvetteri (3.37 %) and T. pubescens (1.96 %), respectively. Gas chromatography-mass spectrometry (GC/MS) identified 42 compounds including thymol, carvacrol, linalool, p-cymene, γ-terpinene, terpinen-4-ol, and α-terpineol as the main compounds. In most cases, selfed plants compared to open pollinated ones, revealed higher thymol content. T. daenensis-1 showed a significant increase in thymol content (from 25.22 % to 74.3 %) due to self-pollination. Moreover, self-pollination led to emergence of some new compounds. Carvacrol methyl ether was the constituents of Thymus EO that are being reported in self-pollinated populations. Finally, inbreeding in Thymus might be suggested as a useful tool to increase genetic homogeneity for the selection of superior plants for improving secondary metabolite.     

Effect of soil application of humic acid on nutrients uptake,essential oil and chemical compositions of garden thyme (<Emphasis Type="Italic">Thymus vulgaris</Emphasis> L.) under greenhouse conditions

Humic acid is natural biological organic, which has a high effect on plant growth and quality. However, the mechanisms of the promoting effect of humic acid on the volatile composition were rarely reported. In this study, the effects of soil application of humic acid on the chemical composition and nutrients uptake of Thymus vulgaris were investigated. Treatments comprised 0, 50, 75 and 100 g m^?2. Essential oil was extracted by hydrodistillation and analyzed using GC–MS and GC–FID. Essential oil content was enhanced by increase of the humic acid level and its content ranged from 0.8% (control) to 2.0% (75 g m^?2). Thirty-two volatile compounds were identified and these compounds were considerably affected by humic acid. The highest percentage of thymol (74.15%), carvacrol (6.20%), p-cymene (4.24%), borneol (3.42%), trans-caryophyllene (1.70%) and cis-sabinene hydrate (1.35%) as major compounds were observed in T. vulgaris under 100 g m^?2 humic acid. There was a linear relationship (R² = 97%) between humic acid levels and thymol as a major compound. The oils were dominated by oxygenated monoterpenes followed by monoterpene hydrocarbons and sesquiterpene hydrocarbons. Based on the path coefficient analysis, the highest direct effects on essential oil content were observed in monoterpene esters (3.465) and oxygenated sesquiterpenes (3.146). The humic acid application also enhanced the uptake of N, P, K, Mg and Fe in garden thyme. The highest N (2.42%), P (0.75%), K (2.63%), Mg (0.23%) and Fe (1436.58 ppm) were observed in medium supplemented with 100 g m^?2 humic acid. In all, the utilization of humic acid could positively change nutrients uptake, essential oil content and its major constituents in T. vulgaris.     

Antifungal activity of thyme (Thymus vulgaris L.) essential oil and thymol against moulds from damp dwellings

AIMS: To characterize antifungal activities of essential oil of thyme (Thymus vulgaris L.) and pure thymol, as comparative substance, on different mould species isolated from damp dwellings. METHODS AND RESULTS: Fifty samples of wall scrapes were collected from damp dwellings in Zagreb, the capital of Croatia. The members of the following mould genera were recovered from the samples: Aspergillus (44%), Penicillium (18%) Alternaria, Ulocladium, Absidia and Mucor (8%) Cladosporium, Trichoderma and Rhizopus (6%), and Chaetomium (2%). Two strains of Stachybotrys chartarum were isolated from damp dwellings in Slovakia. Antifungal activities of the thyme essential oil, which contains p-cymene (36.5%), thymol (33.0%) and 1,8-cineole (11.3%) as main components, and pure thymol were determined by the dilution method and exposure to vaporous phase of the oil. Minimum inhibitory concentrations (MIC) of both thymol and essential oil were bellow 20 microg ml(-1), except for Mucor spp. (50.20 microg ml(-1)). Thymol exhibited approximately three-times stronger inhibition than essential oil of thyme. The vaporous phase of the thyme essential oil (82 microg l(-1)) in glass chambers strongly suppressed the sporulation of moulds during 60 days of exposure. CONCLUSION: The thyme essential oil possesses a wide range spectrum of fungicidal activity. The vaporous phase of the oil exhibited long-lasting suppressive activity on moulds from damp dwellings. SIGNIFICANCE AND IMPACT OF THE STUDY: Essential oil of thyme and thymol could be used for disinfection of mouldy walls in the dwellings in low concentration.     

Chemical composition, antioxidant and antimicrobial activities of essential oil of Thymus algeriensis wild-growing in Libya

The composition of essential oil isolated from Thymus algeriensis growing wild in Libya was analyzed by GC and GC-MS. The essential oil was characterized with thymol (38.50%) as the major component. The oil was screened for antioxidant activity using DPPH assay, and compared to thymol and carvacrol. Antioxidant activity was high, with the IC₅₀ of 0.299 mg/ml, compared to 0.403 and 0.105 mg/ml for thymol and carvacrol, and 0.0717 mg/ml for BHA. In addition, antimicrobial activity was tested against eight bacteria and eight fungi. T. algeriensis oil showed inhibitory activity against tested bacteria at 0.001–0.05 mg/ml, while bactericidal activity (MBC) was achieved at 0.0025–0.05 mg/ml. For antifungal activity MICs ranged 0.0005–0.025 mg/ml and MFC 0.001–0.05 mg/ml. High antimicrobial activity against the fungi in particular suggests that the essential oil of Thymus algeriensis could have a useful practical application.     

<Superscript>1</Superscript>H NMR-based metabolic profiling and target analysis: a combined approach for the quality control of <Emphasis Type="Italic">Thymus vulgaris</Emphasis>

The characterization of T. vulgaris plant material for quality control purposes was performed by NMR-based methods. Direct extraction of 141 T. vulgaris samples with DMSO-d ₆ enabled the obtainment of crude extracts with a representative composition in terms of both volatile and non-volatile constituents. The acquisition of 600 MHz ¹H NMR spectra resulted in a dataset which was analyzed by a combination of metabolic profiling and target analysis approaches. Preliminary analysis of the ¹H NMR spectra was performed by principal component analysis, which revealed sample discrimination on a chemotype basis (thymol, carvacrol and linalool chemotypes). Further minor discriminative constituents were identified as p-cymene, γ-terpinene, rosmarinic acid, and 3,4,3′,4′-tetrahydroxy-5,5′-diisopropyl-2,2′-dimethylbiphenyl. Metabolite identification was accomplished by 1D and 2D NMR techniques and supported by spiking experiments. Fast dereplication of constituents not available as reference compounds was performed by HPLC–SPE–NMR experiments. A targeted approach based on qHNMR was validated for quantification of the identified secondary metabolites. Validation was performed in terms of precision (intra-day RSD ≤ 4.51%, inter-day RSD ≤ 4.18%), repeatability (RSD ≤ 2.30%), accuracy (recovery rates within 93.4 and 103.4%), linearity (correlation coefficients ≥ 0.9990), robustness, and stability. The amount of the dominant monoterpene in thymol, carvacrol, and linalool chemotypes was respectively found to be within 0.4–2.6, 0.7–2.3, and 1.1–3.6% (w/w). Variable amounts of the precursors p-cymene and γ-terpinene were found in thymol and carvacrol chemotypes. The highest amount of rosmarinic acid and 3,4,3′,4′-tetrahydroxy-5,5′-diisopropyl-2,2′-dimethylbiphenyl in the analyzed samples was respectively 4.6 and 0.4% (w/w). Since quantification is performed on a weight basis, the essential oil content can be estimated based on the sum of the quantified monoterpenes. The NMR-based analysis of T. vulgaris represents a more comprehensive approach in comparison to traditional chromatographic methods such as GC and LC, respectively employed for the analysis of volatile and non-volatile constituents. Further advantages lie in the simple sample preparation, rapidity and reproducibility of the NMR analysis.     

Chemical polymorphism of essential oil in Thymus praecox ssp. arcticus (Lamiaceae) from Greenland

The chemistry of the essential oil of Thymus praecox Opiz ssp. arcticus (E. Durand) Jalas from Greenland was studied with the intention of comparing it with the results obtained earlier from Icelandic material. All the 17 samples collected at different localities of South–West Greenland were found to contain linalyl acetate as main component besides some sesquiterpene hydrocarbons and some oxygenated sesquiterpenes. The variable content of the sesquiterpene alcohols, nerolidol and hedycaryol in the essential oil gave reason to define four different chemotypes. The pattern of the chemotype characterizing compounds was identical with that of four of the seven chemotypes found earlier to be the most widely distributed in Iceland, namely chemotypes B, C, D, and F. No correlation between the occurrence of a certain type and special environmental conditions was found. That the essential oil chemistry and the appearance of polychemism in the Greenland Thymus plants accords so well with that of the Icelandic ones, indicates that the distance of nearly 300 km between Iceland and Greenland has not led to locally limited "chemical races" within Thymus praecox ssp. arcticus. These findings are contrary to the results obtained in some Mediterranean Thymus species.     

Differentiating Thymus vulgaris chemotypes with ISSR molecular markers

Common thyme (Thymus vulgaris L.) is a Mediterranean evergreen shrub of the Lamiaceae that shows chemical polymorphism in its natural populations. In Mediterranean habitats six basic chemotypes have been described according to the main component in its essential oil: thymol, carvacrol, linalool, geraniol, α-terpineol, thuyanol-4, of which the thymol chemotype is widely used in cultivation and as a spice. In this study ten selected clones were analysed in terms of chemical composition of the volatile oil and genetic fingerprint. The study question was whether individual chemotypes can be distinguished by molecular markers. Chemical composition was analysed by GC-MS, and for assessing the genetic polymorphism ISSR marker system was chosen as it is reliable and easy to use even in case of less studied species. The studied T. vulgaris clones represented five different chemotypes and could be distinguished using 12 ISSR primers. Clones belonging to the thymol chemotype showed the most distinct separation. The study shows the potential of using molecular markers in breeding and selection of T. vulgaris, being able to differentiate different chemotypes.     

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.     

西双版纳不同热带生态系统土壤有机质的光谱学特性

 为了探讨西双版纳地区土地利用变化对土壤有机质含量及其化学组成的影响,选取了相邻的次生林、耕种6年的农田和定植3年的橡胶园样地,对其0～5 cm和5～20 cm表层土壤中有机质含量、胡敏酸的光谱学特性进行了分析。研究结果表明,次生林转变为农田之后,0～5 cm和5～20 cm 表层土壤有机质含量分别降低33.6%和23.7%;而次生林转变为橡胶园,分别降低28.6%和27.6%。胡敏酸可见-红外光谱结果显示,次生林转变为农田和橡胶园后,0～20 cm表层土壤E4/E6显著降低,这表明胡敏酸化学组成当中芳香族结构增加。傅立叶变换红外光谱结果同样表明,土地利用变化影响土壤有机质的化学组成。次生林转变为农田和橡胶园后,胡敏酸中羧基和酚基结构比例降低,而脂肪族、芳香族和多聚糖比例增加。     

Influence of environmental and genetic factors on the stability of essential oil composition of Thymus pulegioides

Thymus pulegioides plants were collected from various natural habitats of Lithuania and transferred into a new uniform environment. The plants were cloned annually at controlled conditions and their essential oil composition was monitored by capillary GC and GC/MS. The geraniol/geranial/neral (G/G/N), thymol (T), linalool (L), carvacrol/γ-terpinene/p-cymene (C/γT/pC) and thymol/carvacrol/γ-terpinene/p-cymene (T/C/γT/pC) chemotypes of T. pulegioides were studied. It was found that according to the stability of essential oil composition on a sudden change of environmental conditions two types of T. pulegioides can be distinguished: (1) plants which preserve their chemical composition of the essential oils; (2) plants, which considerably change their chemical composition of the essential oils.     

Salicylic acid affects growth,essential oil and chemical compositions of thyme (Thymus daenensis Celak.) under reduced irrigation

Salicylic acid (SA) may reduce the negative impact of water deficit on growth and metabolite yield of Thymus daenensis Celak subsp. daenensis Celak. The effect of foliar application of SA and reduced irrigation on growth, oil yield, chemical components, and antibacterial and antioxidant activities of T. daenensis in field condition were investigated. Treatments comprised 0.0, 1.5 and 3.0 M SA applied to plants under normal irrigation and stressed conditions. Results indicated that irrigation regime had a significant effect on growing degree days (GDD) required to reach early and full flowering. Foliar application of SA influenced GDD from early growing stage to 50 % and full flowering, minimum radius and canopy diameter. The highest values of oil content (3.2 % v/w) and yield (14.9 g m^?2) were obtained from application of 3.0 M SA. Percentage of some chemical constituents in the essential oil extracted from the plants under stress was higher than non-stressed plants. Thymol content was significantly reduced under stressed conditions. Foliar application of SA significantly improved carvacrol, α-thujene, α-pinene and p-cymene contents in the oils, but reduced thymol and, β-caryophyllene amounts. Our results showed that foliar application of SA reduced the negative effect of water deficit on thymol content in the essential oil of T. daenensis. The essential oils of T. daenensis exhibited antioxidant and antibacterial activities when plants were sprayed with 1.5 and 3.0 M SA, respectively.     

Genetic diversity of Ocimum gratissimum L. based on volatile oil constituents, flavonoids and RAPD markers

Morphological, chemical and genetic differences of 12 tree basil (Ocimum gratissimum L.) accessions were studied to determine whether volatile oils and flavonoids can be used as taxonomical markers and to examine the relationship between RAPDs to these chemical markers. Eugenol, thymol, and geraniol were the major volatile oil constituents found in Ocimum gratissimum. Xantomicrol and cirsimaritin were the major external flavones. The accessions morphologically described as O. gratissimum var. gratissimum contained eugenol as the major volatile oil constituent, and cirsimaritin as the major flavone. Ocimum gratissimum var. macrophyllum accessions contained thymol as the major volatile oil constituent, and xantomicrol as the major flavone. A distinct essential oil and flavone chemotype (producing geraniol and a mixture of the flavones cirsimaritin, isothymusin, xanthomicrol, and luteolin) was found in an accession genetically more distant from the other two groups when analyzed by molecular markers. The accessions could be divided based on volatile oil constituents into six groups: (1) thymol: alpha-copaene (ot24, ot25, ot26, and ot28); (2) eugenol:spathulenol (ot17, ot63, and ot52); (3) thymol:p-cymene (ot65); (4) eugenol:gamma-muurolene (ot27 and ot29); (5) eugenol:thymol: spathulenol (ot85); and (6) geraniol (ot84). Cluster analysis of RAPD markers showed that there are three groups that are distinct genetically and highly correlated (r=0.814) to volatile oil constituents.     

GC-MS analysis and in vitro antioxidant and enzyme inhibitory activities of essential oil from aerial parts of endemic Thymus spathulifolius Hausskn. et Velen

We investigated the antioxidant and enzyme inhibitory activities and chemical composition of the hydro-distilled essential oil (0.35% yield) from aerial parts of Thymus spathulifolius. Antioxidant capacity of the oil was assessed by different methods including free radical scavenging (DPPH and ABTS), reducing power (FRAP and CUPRAC) and phosphomolybdenum assay. Inhibitory activities were analyzed against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), α-amylase, α-glucosidase, and tyrosinase. Twenty-one constituents were identified representing 97.2% of the total oil with thymol (50.5%), borneol (16.7%) and carvacrol (7.7%) as the major components. The essential oil exhibited good antioxidant activity with IC₅₀ values of 3.82 and 0.22?mg/mL determined by free radical scavenging DPPH and ABTS, respectively. EC₅₀ values of FRAP and CUPRAC were found to be 0.12 and 0.34?mg/mL, respectively. The results of the present study support the uses of T. spathulifolius essential oil as a source of natural antioxidants and bioactivities for functional foods and phytomedicines.     

Chemical composition and in vitro evaluation of antioxidant effect of free volatile compounds from Satureja montana L

As a part of an investigation of natural antioxidants from Dalmatian aromatic plants, in this paper we report a study of the antioxidant activity related to the chemical composition of savory free volatile compounds. Twenty-one compounds were identified in the essential oil without fractionation, representing 97.4% of the total oil. The major compound was phenolic monoterpene thymol (45.2%). Other important compounds were monoterpenic hydrocarbons p-cymene (6.4%) a nd gamma-terpinene (5.9%)and oxygen-containing compounds carvacrol methyl ether (5.8%), thymol methyl ether (5.1%), carvacrol (5.3%), geraniol (5.0%) and borneol (3.9%). The evaluation of antioxidant power was performed in vitro by the beta-carotene bleaching and thiobarbituric acid (TBA) methods. As determined with both methods, the total savory essential oil as well as different fractions or pure constituents containing hydroxyl group exhibited relatively strong antioxidant effect. The hydrocarbons, when isolated as CH fraction, showed the poorest effectiveness in spite the fact that this fraction contained gamma-terpinene, alpha-terpinene, p-cymene and terpinolene which previously were identified as potential antioxidants.     

Madia sativa,a potential oil crop of central Chile

Madia sativa seeds were studied for their oil content and fatty acid composition. Oil content in wild seeds was 26% w/w. The samples analyzed showed comparable fatty acid composition, with palmitic (12.9–14.0), stearic (3.8–3.9), oleic (7.9-10.2) and linoleic acid (71.4–72.4) as the major acids. The mean molecular weight of the oil ranges from 876.1 to 894.6 with saponification values of 190–194 mg and unsaturation values of 126–131. The seed meal showed a high crude protein content (28–31%). The oil composition of Madia sativa and its adaptability to poor soils, suggest considerable potential as a future oil crop.     

Beneficial effects of thyme oil on age-related changes in the phospholipid C20 and C22 polyunsaturated fatty acid composition of various rat tissues

The aim of this study was to determine any age-related changes in phospholipid polyunsaturated fatty acid composition, in particular C20 and C22 fatty acids in rat liver, brain, kidney and heart, and to assess and compare the effects of dietary supplementation (42.5 mg/kg body weight/day) of the natural antioxidant thyme oil and its major component thymol throughout the rat life span. The fatty acid composition in the various tissues from young (7 months) and aged (28 months) rats was determined and compared. Livers from aged control, thyme oil and thymol treated rats exhibited an increase in 22:6(n-3). In contrast, 22:6(n-3) content of brain, kidney and heart declined in aged rats in all three dietary groups. However, aged rats treated with thyme oil and thymol displayed significantly higher levels of 22:6(n-3) than the respective age-matched controls. Tissue compositions of 20:4(n-6) were found to be significantly lower in the liver and kidney from aged control rats but not those fed either thyme oil or thymol. In aged rats, the composition of 20:4(n-6) in all tissues was highest in rats fed either thyme oil or thymol. These results show that dietary supplementation with thyme oil tended to maintain higher PUFA levels in all tissues studied. The majority of protection provided by thyme oil was by virtue of its thymol component, which comprises 49% of the whole oil. Thymol administered alone did not provide significantly higher protection than the whole oil, suggesting that other components within thyme oil are also contributing antioxidant activity.     

A New Histochemical Method for Localization of the Site of Monoterpene Phenol Accumulation in Plant Secretory Structures

A new method is reported for the histochemical localizationof monoterpene phenols in essential oil secretory structures.The method was adapted from a spot test originally devised forin vitro detection of phenolic compounds in organic analyses.Plant subjects were the Lamiaceae species Thymus vulgaris L.,Oreganum vulgare L. and Mentha x piperita L., which accumulateessential oil in glandular trichomes. A reagent consisting of4-nitrosophenol in conc. H₂SO₄was applied to sample leaves ofeach species. A positive test for phenol was indicated by theproduction of coloured indophenols. Using this method, monoterpenephenols were identified in the trichomes of T. vulgaris(thymol)and O. vulgare(carvacrol), indicated by colour changes to redand green respectively. No phenol was detected in trichomesof M. x piperita. Results were confirmed by GC-MS analysis ofleaf volatile extracts from each species, and in vitro testswith thymol and carvacrol. The method could be used in fieldsurveys for rapid identification of potential medicinal plantsand bioactive compounds. Copyright 2001 Annals of Botany Company Histochemistry, secretory structures, glandular trichomes, Lamiaceae, Thymus vulgaris, Oreganum vulgare, Mentha x piperita, essential oil, aromatic monoterpenes     

Variability of Essential Oil Content and Composition of Origanum vulgare L. Populations from a North Mediterranean Area (Liguria Region, Northern Italy)

Native populations of Origanum vulgare L. from the Liguria andEmilia regions of northern Italy were analysed for essentialoil content and composition. Morphological characters suggestedthat the Ligurian samples belonged to the ssp. viride. The essentialoil content of inflorescences ranged from less than 5 mg g^-1inthe samples from Emilia, to more than 50 mg g^-1in some Liguriansamples, values similar to those reported for ssp. hirtum fromsouthern Italy. Sixty-four compounds were identified in theessential oil. The samples were allotted to three main groupson the basis of oil composition: the first group had a highcontent of components belonging to the carvacrol/thymol biosyntheticpathway; the second was characterized by a different sesquiterpenecomposition and a high linalool content; and the third, includingthe two samples of ssp. vulgare from Emilia, was characterizedby the presence of abundant sesquiterpenes. The high essentialoil content of the samples studied, and the presence of someparticular morphological characters suggest that the taxonomyof O. vulgare, especially in its western distribution area,needs further investigation. Linalool types, although oftennot considered as ‘typical oregano’, may be usefulin promoting wider utilization of the biodiversity of this species.Copyright 2000 Annals of Botany Company Oregano, Origanum vulgare L., ssp. viride, ssp. vulgare, ssp. hirtum, essential oil, gas chromatography, mass spectrometry, genetic resources, chemotypes, quality, Mediterranean