Polyphenol combinations improve quercetin absorption and inhibit carbohydrate digestion while reducing glucose transport

High saccharide intake contributes to the development of obesity and type 2 diabetes. Polyphenols such as quercetin, kaempferol, and isoquercetin have been shown to reduce carbohydrate digestion and monosaccharide uptake. This study examined their individual and combined effects on alpha-amylase and alpha-glucosidase activity using spectrophotometry-based assays as well as on glucose and fructose transport and polyphenol absorption in differentiated Caco-2 cells. Quercetin (200 mu M) significantly inhibited alpha-glucosidase activity by similar to 94%, while similar to 10% inhibition of alpha-amylase activity was observed. A three-polyphenol mixture (equimolar 1 : 1 : 1 quercetin : kaempferol : isoquercetin) significantly inhibited alpha-amylase by similar to 30%. Quercetin and kaempferol (100 mu M) significiantly reduced glucose absorption by similar to 50% and similar to 25%, respectively. A mixture of all polyphenols (100 mu M) significantly reduced glucose absorption by similar to 57%. None of the tested polyphenols altered fructose absorption compared to the control. The mixture doubled quercetin absorption compared to quercetin alone at equal doses, which could be explained by kaempferol's inhibition of efflux transporters. These findings suggest that multi-component polyphenol formulations can enhance alpha-amylase inhibition and quercetin bioavailability while maintaining strong alpha-glucosidase inhibition.