A novel flavonoid from Lespedeza virgata (Thunb.) DC.: Structural elucidation and antioxidative activity

From Lespedeza virgata (Thunb.) DC. five known and one new (1) flavonoids were isolated. This new compound when tested in superoxide anion scavenging assay exerted the highest antioxidant activity (IC 50 = 0.14 mg/ml). Bioactivity guided fractionation of the ethanolic extract of the whole plants of Lespedeza virgata (Thunb.) DC. resulted in the isolation of a novel flavonoid ( 1) along with five known compounds 2– 6. The molecular and structural formula as well as the stereochemistry of compound 1 were determined using data obtained from 1H and 13C NMR spectra, DEPT135 and by 2D HSQC, HMBC, 1H– 1H correlated spectroscopy ( 1H– 1H COSY), and nuclear overhauser effect spectroscopy (NOESY) experiments. The superoxide anion scavenging activities of all isolated compounds were evaluated by the hypoxanthine nitro blue tetrazolium and ESR methods and the new compound 1 showed the strongest antioxidative activity 95.79% (IC 50 = 0.14 mg/ml).