Essential oil variability ofThymus eriocalyx (Ronniger) Jalas

Contribution to the moss flora of northern Sikkim, India

Study of species composition and community structure is an essential requirement for maintaining the ecosystem functions, conservation, and sustainable use. Bryophytes are integral components of biodiversity and resilient during perturbation. The present investigation was, therefore, a survey in North Sikkim district (India) to study the diversity and distribution of mosses resulting in a total of 113 species in 74 genera and 28 families as new records to the study area. Of these, 14 species are considered rare based on their frequency of occurrence. The family Meteoriaceae which consists of mainly epiphytic taxa is found to be dominant and widely spread in the study area followed by Pottiaceae, Leucobryaceae, and Dicranaceae families. Sixteen species are found to be remarkable in contributing major biomass to the forest floors and as epiphytes. Five species are recorded to be endemic to this area. Most of the epiphytic species are found to be abundant in the area, indicating the good health of ecosystem. The data would be useful in the planning of conservation and management of biodiversity.

Chemical Profiles and Insecticidal Potential of Essential Oils Isolated from Four Thymus Species against Rhyzopertha dominica (F.)

Although chemical pesticides have been efficiently used to manage insect pest, their overuse has led to environmental contamination and threats to human health, enticing researchers to introduce eco-friendly and effective agents. In this study, the insecticidal effectiveness of essential oils isolated from Thymus species, including T. eriocalyx, T. kotschyanus, T. fallax, and T. vulgaris, was evaluated against the adults of Rhyzopertha dominica. The terpenes p-cymene, 1,8-cineole, linalool, α-terpineol, and carvacrol were the prominent compounds in the hydrodistilled essential oils. All essential oils produced significant fumigant at 24, 48, and 72-exposure times. The energy reserves protein by all essential oils, glycogen by T. kotschyanus and T. vulgaris, and lipid by T. fallax and T. vulgaris were significantly decreased compared to control. All essential oils except T. vulgaris affected the amylolytic and proteolytic activity of the pest. The pest increased the α- and β-esterase enzyme activity in response to the essential oils. Nutritional indices of adults were also affected by essential oils, in which feeding deterrence index was calculated from 20.41% to 61.11%. Accordingly, based on lethal and extensive sub-lethal insecticidal activities, T. eriocalyx, T. kotschyanus, T. fallax, and T. vulgaris essential oils can be considered as efficient agents for R. dominica management.

Efficacy of Nanoencapsulated Thymus eriocalyx and Thymus kotschyanus Essential Oils by a Mesoporous Material MCM-41 Against Tetranychus urticae (Acari: Tetranychidae)

Inspite of well-established potentiality of plant essential oils as biopesticides, their environmentally low persistence is considered as a hindering obstacle for its commercialization. In the present study, chemical composition and toxicity of essential oils isolated from leaves of Thymus eriocalyx and Thymus kotschyanus were evaluated against two-spotted spider mite, Tetranychus urticae. The chemicals present in the crude oil were found to be thymol (28.83%), oleic acid (11.51%), palmitic acid (8.60%), borneol (5.72%), ρ-cymene (3.60%), and 1,8-cineole (3.57%) in the essential oil of T. eriocalyx, and camphene (35.59%), linalyl acetate (20.47%), linalool (14.75%), α-terpineol (13.87%), and geranyl acetate (3.07%) in the essential oil of T. kotschyanus. The essential oils had strong fumigant toxicity on the adult females of Te. urticae and their fumigation persistence was prolonged until 6 and 5 d, respectively, for T. eriocalyx and T. kotschyanus. Loading of essential oils in MCM-41 increased their stability and persistence was extended up to 20 and 18 d for T. eriocalyx and T. kotschyanus. Further, mite mortality increased from 80 to 203 mites by T. eriocalyx and from 58 to 186 mites by T. kotschyanus nanoencapsulated essential oils. Based on these results, nanoencapsulation of T. eriocalyx and T. kotschyanus essential oils in MCM-41 may be a useful method for their application in the management of Te. urticae.

Expression, crystallization and structure elucidation of γ-terpinene synthase from Thymus vulgaris

The biosynthesis of γ-terpinene, a precursor of the phenolic isomers thymol and carvacrol found in the essential oil from Thymus sp., is attributed to the activitiy of γ-terpinene synthase (TPS). Purified γ-terpinene synthase from T. vulgaris (TvTPS), the Thymus species that is the most widely spread and of the greatest economical importance, is able to catalyze the enzymatic conversion of geranyl diphosphate (GPP) to γ-terpinene. The crystal structure of recombinantly expressed and purified TvTPS is reported at 1.65 Å resolution, confirming the dimeric structure of the enzyme. The putative active site of TvTPS is deduced from its pronounced structural similarity to enzymes from other species of the Lamiaceae family involved in terpenoid biosynthesis: to (+)-bornyl diphosphate synthase and 1,8-cineole synthase from Salvia sp. and to (4S)-limonene synthase from Mentha spicata.

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 ČELAK. (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.

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%), γ-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, γ-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.

Determination and discrimination of intraspecific diversity of Astragalus gossypinus by eco-phytosociological method from west of Iran

Astragalus gossypinus Fischer with wide distribution in Iran belongs to the genus Astragalus (Fabaceae). According to existing references and information, individuals of this species are present in many stations with different ecological conditions. This study carried out for determination and discrimination of intraspecific diversity of Astragalus gossypinus by Eco-phytosociological method from west of Iran. In this method, the principle of data collecting and analyzing based on floristical composition (as floristical markers) of each Endogenous milieu (as the unit of study in Eco-phytosociological method). In this order, application of Endogenous milieu (special station) for data collecting and then their analyzing permit us only determine existence of inter and intraspecific diversity. Then for determinating kind and level of intraspecific diversity (Ecophene, Chemotype, Cytotype, Ecotype ...), can use other studies such as: morphological, anatomical, phytochemical, cytological and etc. In this survey, 29 special stations were studied and 195 species distinguished as companions for Astragalus gossypinus. Then floristic-ecologic data collected from each 29 special stations and analyzed by Anaphyto software (F.C.A, A.H.C, B.O, Marquag methods). Comparison of obtained results on multiple coordinate axes from F.C.A method with results from B.O, Marquag and A.H.C methods led to determination of 7 main groups of Endogenous milieus (special station). Flavonoid analyses were used for determinating kind and level of intraspecific diversity in 7 discriminated groups. Leaves flavonoid components of all collected individuals of Astragalus gossypinus were investigated by TLC method. Obtained data from flavonoid survey analyzed by SPSS and MVSP package with WARD and UPGMA methods. Finally, the results of flavonoid studies confirmed the same 7 groups that identified by floristical composition study and showed intraspecific diversity in chemotype level. So according to these results, we can introduce 7 chemotypes for Astragalus gossypinus from west of Iran. These chemotypes exist in different stations with various ecological conditions.