Mechanistic and conformational studies on the interaction of anti-inflammatory drugs, isoxicam and tenoxicam with bovine serum albumin

The mechanism of interaction of the non-steroidal anti-inflammatory drugs, isoxicam (IXM) and tenoxicam (TXM) with bovine serum albumin (BSA) has been studied using spectroscopic techniques, viz., spectrofluorescence, circular dichroism (CD), UV–visible absorption and FT-IR under simulative physiological conditions. Stern–Volmer analysis of fluorescence quenching data shows the presence of the static quenching mechanism. Thermodynamic parameters (negative ΔH0 and positive ΔS0 values obtained in the present study) revealed that the hydrophobic interactions played a major role in the interaction of these drugs with BSA. The distance, r between the donor (BSA) and acceptor (IXM/TXM) was calculated based on the Forster’s theory of non-radiation energy transfer and the values were observed to be 3.85 nm and 2.60 nm in IXM–BSA and TXM–BSA system, respectively. CD and FT-IR studies indicated that the binding of IXM/TXM to BSA induced conformational changes in BSA. The effect of common ions on the binding of IXM/TXM to BSA has been investigated.