Spectrofluorimetric Study on the Interaction of Iosartan Potassium and Bovine Serum Albumin

The interaction of losartan potassium (LP) with bovine serum albumin (BSA) was studied by fluorescence quenching in combination with UV–Vis spectroscopic method under near physiological conditions. The fluorescence quenching rate constants and binding constants for BSA–LP system were determined at different temperatures. The fluorescence quenching of BSA by LP is due to static quenching and energy transfer. The results of thermodynamic parameters, ∆H (‒134.3 kJ mol ‒1 ), ∆S (‒368 J mol‒1 K ‒1 ) and ∆G (‒24.52 to ‒20.83 kJ mol ‒1 ), indicated that van der Waals interaction and hydrogen bonding played a major role for LP–BSA association. The competitive experiments demonstrated that the primary binding site of LP on BSA was located at site II in sub-domain IIIA of BSA. The distance between LP and a tryptophane unit was estimated to be 3.183 nm based on the Förster resonance energy transfer theory. The binding constant (Ka) of BSA–LP at 298K was 1.932×104 L mol ‒1 . Synchronous fluorescence and three-dimensional fluorescence studies showed that the presence of LP could change the conformation of BSA during the binding