Flavonoids as Human Intestinal Carbohydrate Digestive Enzyme Inhibitors

Flavonoids are the largest family of plant-based (poly)phenolic bioactive compounds, with growing evidence showing health-protecting effects, particularly against diabetes. Some compounds influence glucose metabolism by inhibiting enzymes involved in carbohydrate digestion and suppress intestinal glucose absorption. In this study, the ability of four flavonols (quercetin, kaempferol, quercetagetin and galangin) to inhibit α-glucosidases (sucrase, maltase and isomaltase) were evaluated individually, compared with acarbose and EGCG. Cell-free extracts from human intestinal Caco2/TC7 cells highly expressing brush border α-glucosidases were used. Glucose, sucrose, fructose, isomaltose and maltose were detected using HPAE-PAD with high accuracy, precision and sensitivity. Acarbose showed inhibition of sucrase, maltase and isomaltase activities at comparably lower IC50 values of 1.65, 13.9 and 39.1 µM, respectively. A similar inhibition pattern but higher values were observed with EGCG. Stronger sucrase inhibition was seen with quercetagetin, similar to acarbose, followed by galangin and kaempferol, and weakest by quercetin and EGCG. Similar results were observed for maltase but with a low er inhibition. All flavonols showed a similar isomaltase inhibition to acarboseat a lower inhibition (<29%), while higher EGCG concentration was required to achieve maximum inhibition. This highlights the potential of flavonoids to inhibit human intestinal enzyme activities in the breakdown of carbohydrates.