Spectroscopic and molecular docking studies of the binding of the angiotensin II receptor blockers (ARBs) azilsartan, eprosartan and olmesartan to bovine serum albumin

Angiotensin receptor blockers (ARBs) represent a group of widely used therapeutic agents for the effective control of hypertension and other cardiovascular problems. Herein, the interactions of three important members of the ARBs (azilsartan, eprosartan and olmesartan) with bovine serum albumin (BSA) have been explored employing a set of simple spectroscopic approaches complemented with molecular docking studies. Steady state fluorescence emission results demonstrated the ARBs-induced quenching of the intrinsic fluorescence of BSA, which turned out to be a result of the formation of non-fluorescent complexes. The determined Stern-Volmer and binding constants were in the 104 magnitude, which were declined with the increase in temperature that primarily indicated static type of quenching. Subsequent analysis of the fluorescence data to explore the thermodynamic characteristics of these interactions showed spontaneous reactions with negative ΔH◦ values and positive ΔS◦ values, which suggest the involvement of electrostatic binding forces along with hydrogen bonding. Competitive binding studies were conducted with the aid of known BSA site markers to find the binding region of BSA for the investigated ligands. This was further supported by molecular docking simulations that ascertained the efficient binding of the three ligands to Sudlow site I (subdomain IIA) in the BSA structure.