Isothermal titration calorimetry study of epicatechin binding to serum albumin.

The interaction of epicatechin with bovine serum albumin (BSA) was studied by isothermal titration calorimetry. The binding constant (K) and associated thermodynamic binding parameters (n, DeltaH) were determined for the interaction at three solution concentrations of BSA using a binding model assuming independent binding sites. These data show weak non-covalent binding of epicatechin to BSA. The interaction energetics varied with BSA concentration in the calorimeter cell, suggesting that the binding of epicatechin induced BSA aggregation. The free energy (DeltaG) remained constant within a range of 2 kJ mol(-1) and negative entropy was observed, indicating an enthalpy driven exothermic interaction. It is concluded that the non-covalent epicatechin-BSA complex is formed by hydrogen bonding.