High inhibitory activity of flavonoids from Sophora japonica L. flower buds against α-amylase and α-glucosidase: A mechanistic insight

In this work, a method was developed to screen compounds with enzyme activity inhibition in vitro using chromatographic analysis combined with activity difference analysis (CAADA). The flower buds of Sophora japonica L. (FBSJ) were found to contain abundant flavonoids. These flavonoids were then screened for their high inhibitory activity against α-amylase and α-glucosidase using fingerprint and activity difference analysis. Consistent conclusions were drawn from multiple techniques, including the reported technique, IC50 data, and CAADA. The inhibitory mechanism was further analyzed through enzyme inhibition kinetics, circular dichroism, fluorescence spectrometry, molecular docking, and molecular dynamics (MD). Among the six flavonoid components studied, quercetin was found to act as a competitive inhibitor against α-amylase, while kaempferol showed a mixed manner of inhibition against α-glucosidase. Molecular docking and MD simulations demonstrated that quercetin and kaempferol have higher binding energies and bound more tightly to their targets. In general, flavonols exhibited higher inhibitory activity than their corresponding flavonol glycosides against both α-amylase and α-glucosidase. Quercetin and kaempferol in FBSJ showed potential as inhibitors of α-amylase and α-glucosidase. This study not only presented a novel method for screening compounds with high activity but also provided a theoretical basis for studying the application and mechanism of flavonoids against α-amylase and α-glucosidase in FBSJ.