Complexation of cox-2 inhibitors with bovine serum albumin: interaction mechanism.

Mechanism of interaction of six cox-2 inhibitors--celecoxib, valdecoxib, etoricoxib, parecoxib sodium, meloxicam and nimesulide--with bovine serum albumin (BSA) was studied using fluorescence spectroscopic technique. Results were discussed in terms of the binding parameters, thermodynamics of the binding process, the nature of forces involved in the interaction and the fluorescence quenching mechanism involved. Association constants were of the order of 10(4)-10(5) for various drugs. Binding affinity varied with the nature of drug. Nature of forces involved in the interaction could be predicted from the thermodynamic parameters for the binding. Meloxicam and nimesulide shared common sites with hydrophobic probe, 1-anilinonaphthalene-8-sulfonate (ANS) on BSA molecule. Stern-Volmer analysis of the quenching data indicated that both tryptophan residues of BSA are fully accessible to the drugs and predominantly static quenching mechanism is involved in the interaction.