Flavonoids are known to play a role in hypoglycemia by inhibiting α-glucosidase. However, their interaction mechanism with α-glucosidase still needs to be elaborated. In this study, the α-glucosidase inhibitory activities of 15 flavonoids were investigated. Their molecular volume had a negative effect on inhibitory activity, while the number of phenolic hydroxyl groups on the B ring was positively correlated with inhibitory activity. To explain the significant differences in activity, the interaction behaviors of myricetin and dihydromyricetin, which have similar structures, were compared by spectrofluorimetry, molecular docking, and the independent gradient model (IGM). In the fluorescence analysis, myricetin exhibited a higher binding capacity. Based on molecular docking and IGM analysis, their non-covalent interactions with α-glucosidase could be visualized and quantified. It was found that they had different binding modes with the enzymes and that myricetin possessed stronger hydrogen bonding and van der Waals force interactions, which explained the thermodynamic results.

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Baicalein is one of the main bioactive compounds in Scutellaria baicalensis. In this study, its inhibitory mechanism against α-glucosidase from Saccharomyces cerevisiae was clarified based on experimental and molecular simulation methods. According to HPLC analysis, the α-glucosidase inhibitory activity of S. baicalensis (IC 50 , 6.75 ± 0.08 μg mL −1) was superior to that of acarbose (IC 50 , 2.52 ± 0.12 mg mL −1). The fluorescence results suggested that baicalein could form a complex with α-glucosidase at the molar ratio of 1 under the drive of hydrogen bonding and van der Waals force. Molecular docking showed that baicalein could form hydrogen bonds with Trp391, Arg428, Gly566,and Glu771 of α-glucosidase, and interacted with Phe385, Phe389, Arg387, Glu429, Phe444, Trp789, and Trp710 by hydrophobic force, which coincided with the experimental results. It can be concluded that baicalein is a potential α-glucosidase inhibitor for controlling the postprandial blood glucose level of diabetics.