Protective effect on pancreatic β cells of α-glucosidase inhibitors screened from Rehmannia glutinosa

Abstract

Rehmannia glutinosa (RG) has been traditionally used as Chinese folk medicine for thousands of years. Catalpol in RG has significant therapeutic effects on type 2 diabetes mellitus (T2DM) and its complications. However, very limited study on other chemicals in RG for the treatment of diabetes. In this study, the compounds with α-glucosidase inhibitory activity in RG were screened and isolated by microfractionation bioactivity evaluation method. For the first time, 2,3,5,4′ -tetrahydroxystilbene-2-O-β-D-glucoside (THSG) was found in RG, and the inhibitory type of its enzyme inhibitory activity was determined. In addition, INS-1 cells were treated with H2O2 to establish a model of oxidative damage to pancreatic β cells, and the protective effect of THSG on oxidative damage of INS-1 cells was evaluated by detecting cell viability, content of malondialdehyde (MDA), superoxide dismutase (SOD) and insulin secretion levels. The results showed that THSG had a non-competitive reversible inhibitory effect on α-glucosidase (IC50 = 0.186 ± 0.003 μmol/mL). In the oxidative damage model of INS-1 cells treated with 80 μM THSG, cell viability was increased from 52.13% to 76.26%, content of MDA was decreased by 146.21%, and activity of SOD was increased by 26.27%. Compared with the model group, the total amount of insulin increased by 59.37%. Without the influence of H2O2, the total amount of insulin increased by 22.02% compared with the normal group. These results suggested that THSG could regulate blood glucose by effectively inhibiting α-glucosidase, alleviating oxidative damage to pancreatic β cells, and promoting insulin secretion.