Erythrina variegata L (Fabaceae) has been investigated for isolation of secondary metabolites and evaluation of bioactivities. Previously, we reported re-isolation of alpinum isoflavone (4) and first isolation of 6-hydroxygenistein (5), 3β,28-dihydroxyolean-12-ene (6) and epilupeol (7) from a methanol extract of E. variegata. Now we report three further isoflavones, namely, scandenone (1), 4',5,7-trihydroxy-8-prenylisoflavone (2) and 4’,5,7-trihydroxy-8-methylisoflavone (3), for the first time from this plant. Purified compounds (2, 4 and 5) and crude fractions were subjected to free radical scavenging activity by l,l-diphenyl-2-picrylhydrazyl (DPPH). The crude methanol extract, n-hexane, carbon tetrachloride and chloroform soluble fractions showed moderate antioxidant activity (IC50= 484.4-82.35 ug/ml), while the purified compounds, 4’,5,7-trihydroxy-8-prenyl isoflavone alpinum isoflavone and 6-hydroxygenistein , exhibited high antioxidant activity having IC50 of 6.42, 8.30 and 8.78 jug/ml, respectively. At the same time the standard compound, tert-butyl-1-hydroxytoluene (BUT) demonstrated an ICS0 of 5.88 ug/ml. In the β-glucosidase inhibitory bioassay, the crude methanol extract, n-hexane, carbon tetrachloride and chloroform soluble fractions of E. variegata revealed of 34.75, 95.04, 91.49 and 55.32%, inhibition respectively.
Keywords: Erythrina variegata, Fabaceae, Alpinum isoflavone, Scandenone, 6-Hydroxygenistein, 4',5,7-Trihydroxy-methylisoflavone, 4',5,7-Trihydroxy-8-prenylisoflavone, ß-Glucosidase inhibition, Antioxidant activity