Bioassay-guided isolation of antioxidants from the leaves of Vernonia amygdalina delile, asteraceae

Abstract

3kg air-dried leaves of Vernonia amygdalina was extracted with 96% ethanol to yield 517g extract, which succesively portioned with solvents to obtain 30 g PE, 15g CHCl₃ and 20 g EtOAc. Through bioassay-guided of antioxidant activity, EtOAc fraction was chosen to the next steps. 20g EtOAc fraction was seperated by column chromatography and was purified by crystalization to obtain 3 compounds: V₁ (300mg), V₂ (30 mg) and V₃ (41,3mg) which were characterized as Cynarosid, Luteolin and Cosmosiin respectively. All isolated compounds possessed antioxidant activity meanwhile V₁ and V₂ had the stronger antioxidant effect than standard (Rutin, IC₅₀  = 9,47µM) with the IC₅₀ = 5,8 µM and 4,8µM.