Improving Regulation of Polymeric Proanthocyanidins and Tea Polyphenols against Postprandial Hyperglycemia via Acid-Catalyzed Transformation

A novel protocol was established to synthesize novel α-glucosidase inhibitors (prodelphinidin B gallates) from proanthocyanidins from Chinese bayberry leaves (BLPs) and epigallocatechin gallate (EGCG) via acid-catalyzed transformation, which had improved regulation against postprandial hyperglycemia. Their structural-activity relationship was clarified by enzymatic kinetics, multispectroscopic method, molecular docking analysis, and sucrose loading test. ProDB MG and DG were noncompetitive inhibitors of α-glucosidase with IC50 values of 7.82 and 7.52 μg/mL, respectively. They bound with α-glucosidase spontaneously through van der Waals force and hydrogen bonding interaction, inducing the change of spatial conformation and secondary structure of α-glucosidase. Molecular docking studies suggested that proDB MG and DG attached to another one nonactive pocket with strong affinity. ProDB DG exerted significant improvement of postprandial hyperglycemia in a dose-dependent manner. Hence, proDB MG and DG, potential antidiabetic compounds, alleviate postprandial hyperglycemia by inhibiting α-glucosidase.