Competitive binding of synergistic antioxidant chlorogenic acid and (-)-epigallocatechin gallate with lysozyme: Insights from multispectroscopic characterization, molecular docking and activity evaluation

The individual and combined binding of two active polyphenols, (-)-epigallocatechin gallate (EGCG) and chlorogenic acid (CGA), to lysozyme was studied at the molecular level by multispectroscopic techniques and molecular docking. The thermodynamic parameters obtained from fluorescence data indicated that the main driving force for the binding of CGA to lysozyme was electrostatic interaction while the binding of EGCG was mainly driven by hydrogen bonding and van der Waals' forces. The results of circular dichroism spectroscopy and dynamic light scattering showed that the alpha-helical content and particle size of lysozyme decreased and increased, respectively, in the presence of EGCG and/or CGA. The competitive binding of EGCG and CGA to lysozyme was confirmed by molecular docking. The binding of EGCG and/or CGA inhibited the activity of lysozyme. The combination of EGCG and CGA had synergistic antioxidant activity and cytotoxicity to HeLa cells. Response surface methodology was used to analyze the maximum synergistic antioxidant activity between EGCG and CGA. The lysozyme + EGCG/CGA interaction weakened and enhanced the antioxidant activity and cytotoxicity of EGCG/CGA, respectively. These results would provide ideas for the combined application of EGCG and CGA in the fields of functional foods and pharmaceuticals. (C) 2021 Elsevier B.V. All rights reserved.