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

• Tartary buckwheat contained numerous active compounds for α-glucosidase inhibition. • Ultrafiltration-HPLC-MS/MS was employed to screen and identify α-glucosidase inhibitors. • Myricetin and quercetin exhibited the highest activity to inhibit α-glucosidase. • The inhibitors directly interacted with α-glucosidase via a structure-dependent manner. • A synergistic effect was observed between inhibitors. 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 α-glucosidase inhibition (IC 50 = 0.02 mg/mL). Twelve potential α-glucosidase inhibitors from Tartary buckwheat were screened and identified by the combination of ultrafiltration and high-performance liquid chromatography coupled with mass spectrometry. Myricetin and quercetin exhibited the highest anti-α-glucosidase activity with IC 50 values of 0.02 and 0.06 mg/mL, respectively. These inhibitors manifested different types of inhibition manners against α-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 α-glucosidase inhibitory activity, but glucoside and rutinoside replacement on the C-ring obviously weakened this influence. Furthermore, a synergistic effect was observed between inhibitors with different inhibition manners. [ABSTRACT FROM AUTHOR]