Otostegia persica as a source of natural antioxidants

Abstract The antioxidant activity of different extracts of aerial parts of Otostegia persica. (Burm.) Boiss., Labiateae were evaluated using β-carotene bleaching and lipid peroxidation models. The inhibitory activity of these extracts on the peroxidation of linoleic acid was measured by ammonium thiocyanate in comparison to green tea [Camellia Sinensis. (L.) Kuntze] Ginkgo biloba. L., and butylated hydroxyanisole (BHA). A methanol extract of the plant exhibited the highest antioxidant activity. Five compounds were separated and purified from the methanol extract by column and paper chromatography, respectively. Three isolated flavonols showed significant antioxidant activity comparable to BHA and vitamin E in both methods. These active compounds were identified by UV, IR, 1H and 13C NMR, and MS spectroscopies as morin, kaempferol, and quercetin. The only identified C.-glucoflavone (isovitexin) also exhibited interesting antioxidant activity, but weaker than the flavonols. trans.-Cinnamic acid showed no activity in these methods.