Abstract: A variety of spectroscopic techniques were used to study the inhibitory effect and mechanism of rutin and quercetin on starch-digesting enzymes and their combined effect. The results showed that the types of inhibition of rutin and quercetin on α-amylase were competitive, mainly driven by hydrophobic interactions and hydrogen bonds, and the half maximum inhibitory concentrations (IC50) were 0.36 and 0.22 mg/mL, respectively. The inhibition of α-glucosidase by rutin and quercetin was of mixed type, driven by hydrogen bonds, and the IC50 were 1.30 and 0.362 mg/mL, respectively. Moreover, both flavonoids could combine with α-amylase and α-glucosidase at only one/kind of action site to form a complex, thus inhibiting the activity of the enzymes, and their combinations in different proportions had a synergistic inhibitory effect on α-amylase and α-glucosidase. When the concentration ratio between rutin and quercetin was 7:1 and 3.6:18, the combination index for α-amylase and α-glucosidase was 0.20 and 0.22, respectively, showing the best synergistic inhibitory effect. This study provides a theoretical basis for further research on the interaction mechanism between flavonoids and starch-digesting enzymes, is meaningful for guiding the processing and utilization of edible and medicinal plants rich in flavonoids, and helps to promote the virtuous cycle of the tartary buckwheat industry.

Key words: tartary buckwheat; flavonoids; α-amylase; α-glucosidase; inhibition