Glycosidase inhibitory flavonoids from Sophora flavescens

The methanol extract of Sophora flavescens showed a potent glycosidase inhibitory activity. Active components were identified as well-known flavonoid antioxidants: kushenol A (1), (-)-kurarinone (2), sophoraflavanone G (3), 2'-methoxykurarinone (4), kurarinol (5), 8-prenylkaempferol (6), isoxanthohumol (7), kuraridin (8) and maackian (9). All flavonoids were effective inhibitors of alpha-glucosidase and beta-amylase. Interestingly, lavandulylated flavanones 1-5 had strong alpha-glucosidase inhibitory activities, with IC50 values of 45 mu m, 68,mu m, 37 mu m, 155 mu m and 179 mu m, respectively. Kushenol A (1) which does not bear a 4'-hvdroxy group showed selective a-glucosidase inhibitory activity. Lavandulylated chalcone, kuraridine (8), exhibited IC50 value of 57 mu M against beta-glucosidase, which is the first report of a chalcone displaying glycosidase inhibition. Results showed that 8-lavandulyl group in B-ring was a key factor of the glycosidase inhibitory activities. The inhibition pattern was noncompetitive for alpha-glucosidase, whereas mixed inhibition was observed for beta-amylase.