Flavonoids inhibit the amidolytic activity of human thrombin.

The effect of a group of natural flavonoids on human thrombin amidolytic activity was investigated using a spectrophotometric inhibition assay while information on the kinetics and thermodynamics was obtained using optical biosensor techniques. All the flavonoids tested acted as reversible inhibitors, and the quercetin-thrombin complex was found to be most stable at pH=7.5. Docking analysis indicated that quercetin's inhibitory behavior could be related to its planar structure and low steric hindrance, and to its ability to form a critical H-bond with thrombin His57.