Exploring inhibitory mechanism of gallocatechin gallate on a-amylase and a-glucosidase relevant to postprandial hyperglycemia

The postprandial hyperglycemia of diabetic patients is associated with a -amylase and a -glucosidase, searching safer enzyme inhibitors and deciphering their inhibition mechanism are important. In this study, gallocatechin gallate (GCG) was found to exert strong inhibition on α- amylase and α- glucosidase in the mixed-type and non-competitive manners, respectively. GCG could bind with α- amylase and α- glucosidase to form the complexes, which induced conformational changes of the two carbohydrate digestive enzymes. Docking analysis verified that GCG interacted with pivotal amino acids within the active site of α- amylase, while it bound to a site close to the active site of α- glucosidase, which might affect active site, causing declines in a -amylase and α- glucosidase activities. Moreover, the combination of GCG with acarbose increased the inhibition of α- amylase and α- glucosidase and reduced the dosage of acarbose. This study may provide theoretical basis for designing novel functional foods of GCG for the prevention and treatment of diabetes.