Inhibition effects and mechanisms of three curcuminoids against α-glucosidase.

Turmeric curcuminoids displayed their potential in diabetes treatment, however, their inhibition mechanisms are still unclear. Thence, the inhibition effects and mechanisms of three curcuminoids, ie, curcumin (Cur), demethoxycurcumin (DMC), and bis-demethoxycurcumin (BDMC), against α-glucosidase were investigated. Results showed that BDMC (7.1 μM) and DMC (8.8 μM) presented stronger inhibitory activity than Cur (13.3 μM). Kinetic studies revealed BDMC and DMC both as reversible mixed-type inhibitors, differing from the competitive property of Cur. Multispectral results (SPR, fluorescence spectra, and CD spectra) clarified the binding of three curcuminoids with α-glucosidase caused the changes in enzyme conformation microenvironment to inhibit the activity. Molecular docking clarified the detailed binding interactions of three curcuminoids with α-glucosidase. Mice OTGG assay indicated their ability on reducing postprandial hyperglycemia. Therefore, above findings give the efficacy data support for the development and utilization of turmeric and curcuminoids as hypoglycemic function foods and health supplements.