Abstract

Thymus pubescens Boiss. and Kotschy ex Celak. (Lamiaceae) is a grassy and permanent herb which grows wild in some regions of Iran including West Azarbaijan province. Content, composition and antioxidant activity of the essential oils of both wild populations and cultivated ones were compared in this study. The aerial parts of T. pubescens at the beginning of the flowering stage were collected from provenance (T.pub-w₁₌ Shahindezh mountains & T. pub-w₂₌Salmas mountains), and from a cultivated field of the Agriculture Research Centre (T. pub-F) in West Azarbaijan province in June, 2009. The essential oils were extracted by hydro-distillation in a Clevenger apparatus and yield 0.73 and 0.67% in the wild habitats, and 0.43% in the cultivated one respectively, based on v/w. Analyses of the essential oils by GC/MS allowed to identify 20 and 23 constituents in the wild Thymus populations (T.pub-w₁, T. pub-w₂) representing 98.78 and 98.96% of the oils, respectively. Main constituents of the essential oils were respectively carvacrol (33.49%) (30.16%), thymol (14.19) (15.16), linalool (15.76%) (13.14%), and geranyl acetate (9.59%) (9.08%). Cultivated plants (T. pub-F) presented 24 constituents, representing 96.35% of the oil, whose major components were­ carvacrol (34.37%), thymol (13.48%), borneol (10.17%), linalool (6.4%), 1,3,8-p-menthatriene (8.87%), and pinene (8.48%). Two main chemotypes of essential oils were identified, being carvacrol the main component (30.16 to 34.37%). Furthermore, the antioxidant activity of essential oils of the aforesaid plants using DPPH radical scavenging was determined; all of the extracts manifested almost the same pattern of antioxidant activity as the ascorbic acid (Vit C).

Key words: Thymus pubescens, essential oil, GC/MS, carvacrol-thymol.