Calorimetric, spectroscopic and molecular modelling insight into the interaction of gallic acid with bovine serum albumin

Gallic acid (GA), a naturally occurring plant phenolic acid, effectively used as antioxidant, anti-carcinogenic, antifungal, anti-inflammatory and in anti-human rhinovirus activities. The present study reports in vitro interaction studies of Gallic acid (GA) with bovine serum albumin (BSA) by using isothermal titration calorimetric (ITC), fluorescence, circular dichroism (CD) and molecular modelling studies. The association constant (Ka), standard enthalpy change (ΔHo), standard entropy change (ΔSo) and standard Gibbs energy change (ΔGo) were obtained from ITC. The fluorescence results indicate that there was static quenching mechanism in the interactions of GA with BSA. The synchronous and 3D fluorescence spectroscopy confirms conformational alteration of BSA in presence of GA which is further supported by CD. Molecular docking analysis highlighted that GA binds at Sudlow site I of BSA which also confirmed from site probe experiments. In addition, the molecular dynamics (MD) simulation study of BSA and BSA-GA complex shows that binding of GA at site I of BSA is stable and the binding Gibbs energies from the molecular mechanics/Poisson-Boltzmann surface area method showed that van der Waals forces are the predominant intermolecular forces. This study reflects greater pharmacological significance of GA and highlights its importance in the clinical medicine.