Tea polyphenols bind serum albumins:A potential application for polyphenol delivery

Serum proteins play an important role as drug delivery in the clinical applications. We have determined the binding efficacy of tea catechins ( + )-catechin (C), ( - )-epicatechin gallate (ECG) and ( - )-epigallocatechin gallate (EGCG) with human serum albumin (HSA) and bovine serum albumin (BSA) in aqueous solution at physiological pH. Thermodynamic parameters Delta H-0 -13 to -8 (kJ mol(-1)), Delta S-0 18 to 9 (J mol(-1)K(-1)) and Delta G(0) -14 to -13 (kJ mol(-1)) showed tea catechins bind serum proteins via ionic interactions. The binding efficacy was 40-65% for polyphenol-protein conjugates. Modeling showed the presence of H-bonding, stabilizing catechin-protein conjugation with the free binding energy of -10.65 to -8.81 kcal/mol for catechin-HSA and -9.94 to -9.74 kcal/mol for catechin-BSA conjugates. Catechin conjugation induced major perturbations of the protein conformation. Our studies indicate that serum proteins can transport tea catechins in vitro.