Study on the interaction of (+)-catechin with human serum albumin using isothermal titration calorimetry and spectroscopic techniques

Abstract

In this study, the interaction between (+)-catechin and human serum albumin (HSA) was investigated using isothermal titration calorimetry (ITC), in combination with fluorescence spectroscopy, UV-vis absorption spectroscopy, and circular dichroism (CD) spectroscopy. Thermodynamic investigations reveal that the hydrogen bonding and van der Waals force are the major binding forces in the binding of (+)-catechin to HSA. The binding of (+)-catechin to HSA is driven by favorable enthalpy and unfavorable entropy. Fluorescence experiments suggest that (+)-catechin can quench the fluorescence of HSA through a static quenching mechanism. The obtained binding constants and the equilibrium fraction of unbound (+)-catechin show that (+)-catechin can be stored and transported from the circulatory system to reach its target organ. Binding site I is found to be the primary binding site for (+)-catechin. Additionally, as shown by the UV-vis absorption, synchronous fluorescence spectroscopy and circular dichroism (CD) spectroscopy, (+)-catechin may induce conformational and microenvironmental changes of HSA.