Structural exploration of interactions of (+) catechin and (−) epicatechin with bovine serum albumin: Insights from molecular dynamics and spectroscopic methods

The interaction of two stereoisomeric flavanols (+) catechin (CT) and (−) epicatechin (ECT) with bovine serum albumin (BSA) has been studied using UV–Vis absorption and fluorescence spectroscopy. The binding affinity between flavanols and BSA is investigated through fluorescence quenching. Fluorescence study shows that both flavanols exhibit a strong interaction with BSA at a single binding site. This investigation indicates that CT/ECT may quench BSA fluorescence by the static quenching process due to the formation of ground state complex. The binding pocket of BSA is identified at the site I/II with the interaction of CT/ECT using molecular docking studies. Molecular dynamics simulation (MDS) reported the structural changes of BSA into sturdy α-helix formations owing to the interaction of CT/ECT. During the 200 ns simulation, BSA-ECT complex had lower root mean square deviation values, and undergoes slight structural deformations. The MDS result shows that the binding of CT/ECT with BSA is due to hydrophobic and hydrogen bond interactions, which supports the experimental outcomes. The analysis of radius of gyration confirmed that the BSA-ECT complex possessed a more compact structure. CT and ECT differ in their binding site and structural effects caused by distinct orientational positions at the benzopyran moiety. These findings help us to understand the binding nature of CT/ECT with BSA protein, and the effect of protein during blood transportation process.