Spectroscopic and Thermodynamic Studies on the Binding Interaction of Nicorandil to Bovine Serum Albumin, Supported by Molecular Docking Analysis

Using several spectroscopic methods, such as fluorescence spectroscopy, Fourier transform infrared (FTIR), UV-visible spectroscopy, thermodynamic investigations, and molecular modeling (MD), is a recent trend in investigating the binding interactions between pharmaceuticals and proteins. The current research examines how nicorandil (NCL) interacts with bovine serum albumin (BSA), a major blood plasma carrier protein, under simulated physiological circumstances (pH 7.4). Fluorescence data and ultraviolet spectra proved that the intrinsic fluorescence of BSA was diminished by NCL through an integration of dynamic and static quenching mechanisms. Studies indicated that NCL binds weakly to BSA with a single binding site (6.35 × 10² M^-1 at 298 K), which is consistent with the reported plasma protein binding percentage (approximately 25%). Analysis of the thermodynamic parameters revealed that the NCL-BSA interaction was spontaneous with an enthalpy change (ΔH) of 174.85 kJ mol^-1. Hydrophobic forces were the primary binding forces; the entropy change (ΔS) was 639.96 kJ mol^-1. Competitive binding experiments proposed that NCL was primarily attached to Site I of BSA's hydrophobic cavity. In addition, synchronous fluorescence spectroscopy, FTIR, and ligand-protein docking studies have deduced the conformational alteration in the BSA secondary structure when it interacts with NCL. Docking results were in accordance with experimental results.