DETERMINATION OF ESSENTIAL OIL AND POLYPHENOLIC COMPOUNDS IN THYMUS SPECIES

Abstract

Thymus pannonicus All., T. glabrescens Willd., T. pulegioides L., T. praecox Opiz and Thymus serpyllum L., indigenous collective species in the Hungarian flora, were involved in our studies. Content and composition of essential oils and polyphenolic fractions were examined in grown populations, originating from different wild habitats, at the Experimental Station of the Corvinus University of Budapest, in 2009-2010. Essential oil analyses were performed by GC after hydrodistillation. HPLC-DAD and on-line mass spectrometry (ESI-MS) method was used for the measurements of polyphenols. Almost all grown populations of Thymus pannonicus, T. glabrescens and T. serpyllum met the requirements (min. 3 ml/100 g essential oil) of the Pharmacopoeia Hungarica concerning dried flowering parts. According to the GC analysis, it can be concluded that taxa belonging to T. praecox possess sesquiterpene dominated chemotypes with main components of germacrene-D, β-caryophyllene, β-bisabolol, β-cadinene, germacrone and elemol, while Thymus pannonicus, T. glabrescens and Thymus pulegioides populations contain mainly monoterpenes in the essentail oils such as thymol, carvacrol, geraniol, p-cymene, γ-terpinene and thymol methyl ether. The chemotype pattern of the examined Thymus serpyllum population was unique because its essential oil was dominated by 1,8-cineol. The polyphenolic pattern in the same samples of the Thymus species involved was also characterized. The dominant compound was rosmarinic acid, which ranged between 83.49 µg g-1 and 1.436 mg g-1. Other phenolic acids (ferulic acid, caffeic acid, chlorogenic acid and p-coumaric acid) were present in every examined Thymus species, as well as flavanones: naringenin, eriodictyol and dihydroquercetin; flavones: apigenin and apigenin-7-glucoside, flavonols: quercetin and rutin. The polyphenolic composition was found to be a useful additional chemotaxonomic tool for classification purposes and for evaluating the drug quality. Promising taxa of high essential oil and polyphenol accumulating ability and quite constant essential oil pattern have been selected for further breeding and cultivation.