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 ΔH0 −13 to −8 (kJ mol−1), ΔS0 18 to 9 (J mol−1K−1) and ΔG0 -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.