Characterization of binding interactions between selected phenylpropanoid glycosides and trypsin

Phenylpropanoid glycosides (PPGs) are important bioactive polyphenolic compounds that are widely distributed in plants. In this paper, the inhibitory effects of four selected PPGs against trypsin were investigated. The interactions between these PPGs and trypsin were further investigated by multiple spectroscopic methods and molecular docking studies. The results showed that the binding of each of these PPGs to trypsin induced changes in the natural conformation of trypsin, which inhibited the enzyme in the following order: acteoside > syringalide A 3'-alpha-L-rhamnopyranoside > lipedoside A-I > osmanthuside B. The binding constant (K-a) values followed the same trend. The hydrogen bond force played an important role in the interaction between each PPG and trypsin. Interestingly, the binding affinity and inhibitory effect increased as the number of phenolic hydroxyl groups increased. In addition, the effect of the phenolic hydroxyl group on the A ring had a greater effect than one on the B ring.