Variation in essential oil composition of Teucrium hircanicum L. from Iran-A rich source of (E)-α-bergamotene.

In present work, the chemical composition of the essential oils obtained from dried flowering aerial parts of Teucrium hircanicum L. (Labiatae) originated from ten wild populations in Iran was analyzed by a GC-FID and GC/MS system. The oil yields varied from 0.04% to 0.1%. A total of thirty-two compounds representing 67.6-97.7% of the oil were identified. The essential oil was found to be rich in sesquiterpene hydrocarpons (E)-α-bergamotene (17.5-86.9%) and (E)-ß-farnesene (0.5-21.4%). Of the total identified compounds, sesquiterpene hydrocarpons (36.1-89.7%) were included the greatest essential oil fraction in all the populations, followed by oxygenated monoterpenes (2.2-21.6%), oxygenated sesquiterpenes (0.0-14.4%) and monoterepene hydrocarbons (0.0-9.5%). Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) were used to distinguish any geographical variations, indicating that the clustering of populations is related to their geographic origin. According to the GC/MS analysis, two chemotypes consisting of (E)-α-bergamotene and (E)-α-bergamotene-(E)-ß-farnesene were identified in the populations.

Effect of prolonged water stress on essential oil content, compositions and gene expression patterns of mono- and sesquiterpene synthesis in two oregano (Origanum vulgare L.) subspecies.

Origanum vulgare L., recognized throughout the world as a popular medicinal and flavoring herb, contains a wide array of medicinally active components, including phenolic glucosides, flavonoids, tannins, sterols and high amounts of terpenoids. Especially the latter are often extracted by hydrodistillation resulting in the so-called essential oil that is rich in monoterpenes (e.g. carvacrol, thymol, linalyl acetate) and/or sesquiterpenes (e.g. (E)-ß-caryophyllene, germacrene D, bicyclogermacrene, ß-caryophyllene oxide). Water stresses in the arid and semiarid regions of the world severely affect growth and productivity of oregano. To determine the variation in essential oil and gene expression pathway of Iranian oregano under prolonged water stress, two native subspecies of O. vulgare (subsp. virens and subsp. gracile) were studied. The plants, grown in pots, were subjected to three water stress conditions, i.e. no stress, mild stress (60± 5% FMC) and moderate stress (40± 5% FMC). The studied subspecies exhibited significant differences in essential oil content, compositions, and patterns of gene expression under water stress conditions. The essential oil of O. vulgare subsp. gracile was rich in the phenolic monoterpene carvacrol (46.86-52.07%), whereas the sesquiterpene hydrocarbon (Z)-α-bisabolene (39.17-42.64%) was the major constituent in the oil of O. vulgare subsp. virens. Both the mild and moderate water stresses significantly increased the essential oil content of O. vulgare subsp. gracile, but did not significantly change the essential oil content of O. vulgare subsp. virens nor the level of carvacrol and (Z)-α-bisabolene in the investigated subspecies. Interestingly, the amount of (E)-ß-caryophyllene in O. vulgare subsp. virens was significantly increased under water stress conditions. Gene expression studies supported the above findings and demonstrated that there are two different pathways affecting the biosynthesis of the terpenoid precursors geranyl pyrophosphate (GPP) and farnesyl pyrophosphate (FPP). In O. vulgare subsp. gracile, HMGR, Ovtps2 and CYP71D180 transcript were up-regulated under mild and moderate water stress conditions. Transcription of FPPS was apparently down-regulated in water-stressed O. vulgare subsp. gracile. Investigation of terpene synthases expression levels in oregano subspecies demonstrated that Ovtps2 and Ovtps6 controlled the concentration of carvacrol and (E)-ß-caryophyllene in oregano essential oils, respectively.

Assessment of genetic and chemical variability in Thymus caramanicus.

Thymus caramanicus is an endemic species grown in Iran with interesting pharmacological and biological properties. In the present work, essential oil compositions and inter-simple sequences repeat (ISSR) markers were used to estimate the relationships among and within seven populations of T. caramanicus, belonging to three provinces in Iran. The studied individuals were distinguished on the basis of ISSR markers and constituents of essential oil. A total of 127 band positions were produced by 12 ISSR primers, of which 105 were found polymorphic with 82.68% polymorphism. Genetic similarity values among individuals ranged between 0.15 and 0.82 which was indicative of a high level of genetic variation. On the basis of their genetic similarities, ISSR analysis allowed to group the samples into two main clusters. One of these included populations originated from Kerman and Isfahan provinces, and the other cluster consists of populations from Semnan province. Chemical compounds of essential oils were found variable in the various individuals and all samples were principally composed of phenolic constituents (carvacrol and/or thymol). As a consequence, the plants were classified into two major chemotypes including carvacrol and thymol/carvacrol. A relationship between genetic and chemical variability and geographic distribution has been observed in studied populations of T. caramanicus.

Genetic diversity and chemical polymorphism of some Thymus species.

To ascertain whether there are chemical and genetic relationships among some Thymus species and also to determine correlation between these two sets of data, the essential-oil composition and genetic variability of six populations of Thymus including: T. daenensis CELAK. (two populations), T. fallax FISCH. & C.A.MEY., T. fedtschenkoi RONNIGER, T. migricus KLOKOV & DES.-SHOST., and T. vulgaris L. were analyzed by GC and GC/MS, and also by randomly amplified polymorphic DNA (RAPD). Thus, 27 individuals were analyzed using 16 RAPD primers, which generated 264 polymorphic scorable bands and volatiles isolated by distillation extraction were subjected to GC and GC/MS analyses. The yields of oils ranged from 2.1 to 3.8% (v/w), and 34 components were identified, amounting to a total percentage of 97.8-99.9%. RAPD Markers allowed a perfect distinction between the different species based on their distinctive genetic background. However, they did not show identical clustering with the volatile-oil profiles.

Identification and quantification of leaf surface flavonoids in wild-growing populations of Dracocephalum kotschyi by LC-DAD-ESI-MS.

Dracocephalum kotschyi Boiss. (Lamiaceae) is an aromatic and perennial herb endemic to Iran with interesting pharmacological and biological properties. The flavonoids luteolin-7-O-glucoside, apigenin-7-O-glucoside (cosmosiin), luteolin 3'-O-ß-d-glucuronide, luteolin, apigenin, cirsimaritin, isokaempferide, penduletin, xanthomicrol, calycopterin and the polyphenol rosmarinic acid were identified among 13 natural populations of the plant by ESI-MS, LC-DAD and LC-DAD-ESI-MS. The plant extracts containing the identified compounds showed significant antioxidant activity, which was correlated with the flavonoid content. Additionally, leaf and stem size and geographical variability among the studied populations were correlated with flavonoid accumulation. Canonical correlation analysis was used to find a relationship between plant dimensions and phytochemical composition, and the plants with the lowest growth indices were found to have the highest levels of methoxylated flavonoids.

Chemical diversity among the essential oils of wild populations of Stachys lavandulifolia VAHL (Lamiaceae) from Iran.

The variation of the essential-oil composition among ten wild populations of Stachys lavandulifolia VAHL (Lamiaceae), collected from different geographical regions of Iran, was assessed by GC-FID and GC/MS analyses, and their intraspecific chemical variability was determined. Altogether, 49 compounds were identified in the oils, and a relatively high variation in their contents was found. The major compounds of the essential oils were myrcene (0.0-26.2%), limonene (0.0-24.5%), germacrene D (4.2-19.3%), bicyclogermacrene (1.6-18.0%), δ-cadinene (6.5-16.0%), pulegone (0.0-15.1%), (Z)-hex-3-enyl tiglate (0.0-15.1%), (E)-caryophyllene (0.0-12.9), α-zingiberene (0.2-12.2%), and spathulenol (1.6-11.1%). For the determination of the chemotypes and the chemical variability, the essential-oil components were subjected to cluster analysis (CA). The five different chemotypes characterized were Chemotype I (germacrene D/bicyclogermacrene), Chemotype II (germacrene D/spathulenol), Chemotype III (limonene/δ-cadinene), Chemotype IV (pulegone), and Chemotype V (α-zingiberene). The high chemical variation among the populations according to their geographical and bioclimatic distribution imposes that conservation strategies of populations should be made appropriately, taking into account these factors. The in situ and ex situ conservation strategies should concern all populations representing the different chemotypes.

Influence of some environmental factors on the essential oil variability of Thymus migricus.

Essential oils of the air-dried aerial parts of five populations of Thymus migricus Klokov & Desj.-Shost. collected from northwest Iran were obtained by hydrodistillation with yield of 1.1 - 3.3% (w/w). The essential oils were analyzed by a combination of GC-FID and GC-MS techniques, to check for chemical variability. According to populations, twenty-nine components, representing 97.3 - 99.3% of the total components, were identified. Oxygenated monoterpenes were the main group of constituents in all samples (65.2 - 78.5%). Thymol (46.6 - 72.5%), gamma-terpinene (6.2 - 16.7%), p-cymene (4.0 - 6.5%), n-hexadecanol (0.4 - 6.5%), geraniol (0.5 - 4.7%), limonene (0.0 - 3.5%) and carvacrol (0.5 - 3.4%) represented the major compounds. Two chemotypes were identified: thymol and thymol/linalool. In addition, canonical correlation analysis between some essential oil characters and some environmental factors revealed a significant relationship between oil components and environmental factors. The influence of environmental factors over p-cymene, gamma-terpinene, linalool and thymol was evident. Essential oil yield was fairly strongly related to the concentrations of Ca2+ and K+, percentage of organic matter, altitude, temperature, and soil texture.