Variations in Chemical Composition and Bioactive Compounds of Thymus kotschyanus Boiss. & Hohen Populations Originated from Different Collection Sites

Abstract Variations in essential oil yield and oil composition of Thymus kotschyanus Boiss. & Hohen populations originating in different locations across Iran were evaluated using hydrodistillation and GC/MS analysis. The aerial parts of the plants varied in their essential oil yields from 1 to 1.41% across the populations. Under optimum distillation and analysis conditions, thirty-eight constituents accounting for about 88.7-99.9 % of the total components were identified with thymol (6.8-66.15%), carvacrol (2.38-20.06%), linalool (1.39-22.23%), α-terpineol (0.16-11.64%), and geraniol (0.36-11.37%) as the major compounds. Plant samples were also analyzed for their flavonoid and total phenolic contents. Results indicated that total phenolic content of the essential oil from T. kotschyanus Boiss. & Hohen populations ranged from 25.04 to 60.25 mg TAE g-1 DM while total flavonoid content ranged from 2.11 to 8.14 mg QE g-1 DM. Antioxidant activity was assessed by the two complementary analytical approaches of DPPH free-radical scavenging and reducing power systems to discover that both methods revealed comparable antioxidant activities in the extracts, with the highest values belonging to populations 1 (IC50:256.6 μg mL-1) and 5 (IC50:259 μg mL-1). The populations with high thymol contents and antioxidant activities will promise beneficial as supplements in functional food ingredients and pharmaceutical products.