Spectroscopic studies on <i>in vitro</i> binding of cefixime and tolcapone drugs with serum albumin

The interaction between cefixime (antibacterial) and tolcapone (Parkinson’s disease) drugs with bovine serum albumin (BSA) was investigated using several spectroscopic techniques viz. UV–Vis, fluorescence and circular dichroism. The thermodynamic parameters of the interactions were calculated, which indicated that the binding processes are spontaneous and H-bonding and van der Waals forces play a major role in BSA–cefixime interaction and hydrophobic interactions dominate BSA–tolcapone complexation. Cefixime quenches the intrinsic fluorescence of BSA by dynamic process while tolcapone through static process. The binding constant of the BSA–tolcapone complex (10⁷ L mol⁻¹) is found to be relatively higher than that of BSA–cefixime complex (10⁴ L mol⁻¹). The binding distance between BSA and cefixime and tolcapone is calculated to be 3.3 and 4.2 nm, respectively. Both fluorescence and circular dichrosim spectral studies confirmed conformational changes in BSA upon binding with these drugs. Molecular docking studies suggest the possible binding sites in the protein molecule.'