No abstract

The influence of 16 flavonoids on yeast a-glucosidase and /?-fructosidase was investigated. Either />-nitrophenyl-aD -glucopyranoside or maltose was used as substrate for a-glucosidase, and sucrose for jS-fructosidase. Quercetin, myricetin, fisetin, and quercitrin strongly inhibited aglucosidase at 0.1 mM.The concentrations which gave 50% inhibition were 4, 8, 8, 20, and 20jum for myricetin, quercetin, fisetin, kaempferol, and quercitrin, respectively. The mode of inhibition was found to be mixed type, close to non-competitive type with quercetin and quercitrin. Fisetin, naringenin, and morin showed mixed type inhibition. Albumin from bovine serum slightly affected the anti-a-glucosidase activity of quercetin. The flavonoids tested exhibited little effect on /?fructosidase activity at 0.1 mM.