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 IC(50) values of 45 microM, 68 microM, 37 microM, 155 microM and 179 microM, respectively. Kushenol A (1) which does not bear a 4'-hydroxy group showed selective alpha-glucosidase inhibitory activity. Lavandulylated chalcone, kuraridine (8), exhibited IC(50) value of 57 microM 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.