Abstract: Developing food-derived α-glucosidase inhibitors is one of the most important research topics in the area of functional food because α-glucosidase is closely related to postprandial glucose levels in diabetic patients. It has been reported that an extract of liquorice has α-glucosidase-inhibitory activity, which may be partly attributed to the presence of isoliquiritigenin as one of the major bioactive components in liquorice. Given this background, the α-glucosidase-inhibitory mechanism of isoliquiritigenin was investigated by using enzyme inhibition measurement, fluorescence quenching and molecular docking in the present study. It was found that isoliquiritigenin inhibited α-glucosidase in a mixed competitive and noncompetitive mode, and its performance was superior to that of acarbose. The fluorescence quenching analysis showed that under the action of hydrophobic forces, isoliquiritigenin and α-glucosidase could combine with each other to form a complex with one binding site. The molecular docking results coincided with the experimental results. Isoliquiritigenin, located in the hydrophobic pocket of α-glucosidase, formed hydrogen bonds with Asp202 and Arg400, and interacted with the many surrounding hydrophobic residues by hydrophobic forces, thereby maintaining the structure of the complex. These obtained results are helpful to develop novel food-derived α-glucosidase inhibitors and promote the application of isoliquiritigenin in the fields of functional food and medicine.

Key words: isoliquiritigenin, α-glucosidase, inhibition, fluorescence spectroscopy, molecular docking