Natural 8-C-ascorbyl-(−)-epigallocatechin as antidiabetic agent: α-glucosidase and PTP-1B signaling pathway dual regulators

α-Glucosidase and protein tyrosine phosphatase 1B (PTP1B) signaling pathway dual regulators decrease postprandial blood glucose levels and improve insulin sensitivity, making it a new treatment strategy for type 2 diabetes. This study examined in vitro antidiabetic activities of 8-C-ascorbyl-(-)-epigallocatechin (AE), found in oolong tea. AE inhibited α-glucosidase (IC50 = 142.8 μM) with activity higher than that of acarbose (IC50 = 250.2 μM). AE significantly promoted glucose-consumption and activated the insulin signaling pathway through enhancing the protein levels of p-GSK3β and p-Akt and inhibiting the expression of PTP1B, along with slightly inhibitory activity against PTP1B. Docking analysis showed AE inhibited α-glucosidase activity via binding to the catalytic site through hydrogen bonds and Pi-Pi interactions, as well as a good shape match to the active pocket. In addition, AE could relieve oxidative damage and possessed good antioxidant capacity. Taken together, the results of this study indicate that AE exhibits antidiabetic activity in vitro, making it a potential functional food ingredient and drug candidate for management of type 2 diabetes.