THYMUS ALTERNANS KLOKOV: DATA REGARDING THE CHEMICAL COMPOSITION AND ANTIMICROBIAL ACTIVITY OF ESSENTIAL OILS

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgemviennagreen.org, SGEM2017 Vienna GREEN Conference Proceedings, ISBN 978-619-7408-29-4 / ISSN 1314-2704, 27 - 29 November, 2017, Vol. 17, Issue 63, 405-412 pp; DOI: 10.5593/sgem2017H/63/S25.052

ABSTRACT

Thymus alternans is a relatively new species for Romania, being first mentioned in Romanian flora in 2002. The species is quite similar to Thymus pulegioides L., shows hairy stems on opposite sides, alternating from one node to another, leaves are oblong elliptical, ciliate on margins, 2-4 pairs of lateral veins weak prominent and hairy calyx tube. The species grows in mountain meadows at low altitudes (500-1100 m). In this paper, the chemical variability of essential oils and also, their antimicrobial activity was analysed in relations to different phenophases (vegetative, anthesis and fruiting), during two consecutive year. The dried aerial parts of the plant were subjected to hydro-distillation, using a NeoClevenger apparatus, according to the method recommended by the European Pharmacopeia. The chemical composition of the essential oil was established by GC-MS analysis, while the antimicrobial activity was performed on 3 test microorganisms (Staphylococcus aureus, Escherichia coli and Candida albicans), using the diffusion method and the microplate method. Regarding the chemical composition, the highest number of compounds (34) was registered for the vegetative and anthesis stages in the first year, while the least compounds (26) were recorded in the fruiting stage in the second year. In the first year the essential oils had higher amounts of geraniol, thymol, geranil acetate and in the second year methyl thymol and carvacrol were more abundant. In the vegetative stage, o-cymene, methyl thymol, carvacrol are present in higher concentrations while geraniol and geranil acetate register higher quantities in the anthesis or fruiting stages. All tested essential oils inhibited the growth and development of the 3 test microorganisms used. Bacterial growth inhibition areas were, generally, between 5 and 20 mm and fungi inhibition areas were of 5-6 mm. The available literature records very few information regarding chemical composition and antimicrobial activity of essential oils of Thymus alternans. Therefore, the current results may serve as a basis for a biotechnological cultivation of Thymus alternans with higher yield and optimum essential oil composition.

Keywords: thyme, volatile oil, chemical variability, GC-MS, antimicrobial testing