Mechanistic Insights into the Inhibitory Activities of Chemical Constituents from the Fruits of Terminalia boivinii on α-Glucosidase.

Abstract

Regulation of key digestive enzymes is currently considered an effective remedy for diabetes mellitus. In this study, bioactive constituents were purified from Terminalia boivinii fruits and identified by 1 H-NMR, 13 C-NMR and EI-MS. In vitro and in silico methods were used to evaluate α-glucosidase, α-amylase, and lipase inhibition activities. Compounds 1, 2, and 4-7 with IC50 values between 89 and 445 μM showed stronger α-glucosidase inhibitory activities than the antihyperglycemic drug acarbose (IC50 =1463.0±29.5 μM). However, the compounds showed lower inhibitory effects against α-amylase and lipase with IC50 values above 500 μM than acarbose (IC50 =16.7±3.5 μM) and ursolic acid (IC50 =89.5±5.6 μM), respectively. Lineweaver-Burk plots showed that compounds 1, 2, and 7 were non-competitive inhibitors, compounds 4 and 5 were competitive inhibitors and compound 6 was a mixed-type inhibitor. Fluorescence spectroscopic data showed that the compounds altered the microenvironment and conformation of α-glucosidase. Computer simulations indicated that the compounds and enzyme interacted primarily through hydrogen bonding. The findings indicated that the compounds were inhibitors of α-glucosidase and provided significant structural basis for understanding the binding activity of the compounds with α-glucosidase.