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In this work, the inhibitory effect of two isoflavonoids including daidzein and genistein on trypsin and their binding mechanism were determined by spectroscopic and molecular docking approaches. The results indicated that both daidzein and genistein reversibly inhibited trypsin in a competitive manner with IC 50 values of 68.01 × 10 −6 mol L −1 and 64.70 × 10 −6 mol L −1 and K i values of 62.12 × 10 −6 mol L −1 and 59.83 × 10 −6 mol L −1 , respectively. They could spontaneously bind with trypsin mainly through hydrophobic force and electrostatic interactions with a single binding site. Analysis of circular dichrosim spectra and molecular docking revealed that both isoflavonoids bound directly into the catalytic cavity and the microenvironment and secondary structure of trypsin were changed in this process, which caused the inhibition of trypsin activity. All these experimental results and theoretical data in this work would be help in understanding the mechanism of inhibitory effects of daidzein and genistein against trypsin and the potential of isoflavonoid to relieve symptoms of pancreatitis. [ABSTRACT FROM AUTHOR]

Highlights: [•] The interaction between silybin and pepsin was investigated by spectral and docking methods. [•] The hydrophobic interaction was the main mode for stabilizing the silybin-pepsin complex. [•] Synchronous and three-dimensional fluorescence spectra of silybin-pepsin were showed in paper. [•] The interaction of pepsin with silybin occurred in the hydrophobic cavity of pepsin. [•] The effect of silybin on pepsin activity was first investigated in rats. [ABSTRACT FROM AUTHOR]