Inhibitory activities of kaempferol, galangin, carnosic acid and polydatin against glycation and -amylase and -glucosidase enzymes

The activities of four natural phenolics, kaempferol, galangin, carnosic acid and polydatin in scavenging free radicals, inhibiting advanced glycation end-product (AGE) formation, -amylase and -glucosidase and trapping methylglyoxal (MGO), were evaluated in this study. Carnosic acid and galangin had the highest activity in scavenging free radicals. Kaempferol and galangin had the greatest activity in preventing bovine serum albumin (BSA) against glycation and reducing glycated proteins. Polydatin had the greatest performance in trapping MGO to reduce glycation reaction. However, there was no significant difference for kaempferol, galangin and carnosic acid in inhibiting AGE formation by BSA-MGO reaction. Kaempferol, galangin and carnosic acid were the competitive inhibitors for -amylase, while kaempferol and carnosic acid were noncompetitive inhibitors for -glucosidase. However, polydatin showed as a mixed noncompetitive inhibitor for both -amylase and -glucosidase. The results indicated that the four natural phenolics have potential in inhibiting AGE production and the digestive enzymatic activity with different mechanisms.