Inhibition mechanism of a-glucosidase inhibitors screened from Tartary buckwheat and synergistic effect with acarbose

Tartary buckwheat has been shown to provide a good antihyperglycemic effect. However, it is unclear which active compounds play a key role in attenuating postprandial hyperglycemia. Presently, acetone extract from the hull of Tartary buckwheat had the best effect for a-glucosidase inhibition (IC50 = 0.02 mg/mL). Twelve potential a-glucosidase inhibitors from Tartary buckwheat were screened and identified by the combination of ultrafil-tration and high-performance liquid chromatography coupled with mass spectrometry. Myricetin and quercetin exhibited the highest anti-a-glucosidase activity with IC50 values of 0.02 and 0.06 mg/mL, respectively. These inhibitors manifested different types of inhibition manners against a-glucosidase via direct interaction with the amino acid residues. The results of structure-activity relationships indicated that an increase in the number of -OH on the B-ring greatly strengthened a-glucosidase inhibitory activity, but glucoside and rutinoside replace-ment on the C-ring obviously weakened this influence. Furthermore, a synergistic effect was observed between inhibitors with different inhibition manners.