Hypoglycaemic effect of all-trans astaxanthin through inhibiting α-glucosidase

The hypoglycaemic effect of all-trans astaxanthin is long known for its antioxidation for type 2 diabetes, a global health concern. To reduce glycaemic index of type 2 diabetes, inhibition of key enzymes is an efficient approach, for example to inhibit α-glucosidase. Conventional chemical or synthetic enzyme-inhibitors have adverse side effects. Therefore, we studied the inhibition of α-glucosidase by all-trans astaxanthin. To inhibit α-glucosidase, the half maximal inhibitory concentration (IC50) of all-trans astaxanthin was 67.95 ± 0.03 μmol/L. All-trans astaxanthin inhibited α-glucosidase as a competitive inhibitor, as shown by kinetic analysis. All-trans astaxanthin could induce the changes of the secondary structure to reduce α-glucosidase activity. Molecular-docking analysis reveals that all-trans astaxanthin prevented substrate from binding to α-glucosidase by occupying the space of the active pocket to cause the inhibition. Our findings suggest that all-trans astaxanthin has the hypoglycaemic effect through inhibiting α-glucosidase, in addition to its antioxidation effect reported earlier.