Vol. 3, Issue 4, Part J (2017)

Abstract
The plasma protein binding profile of a drug molecule plays a vital role to comprehend the pharmacokinetics and pharmacodynamics properties of that molecule. It has arisen a great concern since it intensely effects drug distribution process and regulates the free fraction. The present study has been done to investigate the interaction of Imipramine hydrochloride (IPM) with bovine serum albumin (BSA) under physiological condition (pH 7.40) using UV absorption and fluorescence spectrophotometry at different temperatures (298K and 308K). To obtain a detail and insightful information of protein binding of Imipramine hydrochloride with BSA, UV-visible and fluorescence spectroscopy were used. Quenching of BSA was also observed in presence of IPM by the fluorescence method. Quenching constants were determined at different temperatures (298K and 308K) using the Stern-Volmer equation. The thermodynamic parameters namely, enthalpy change (∆H), entropy change (∆S), and Gibb’s free energy change (∆G) were analysed based on Van’t Hoff equation. It was found that with the increase of temperature, the value of Stern-Volmer constant increases in case of IPM. From this quenching mechanism, it was found that quenching of BSA-IPM system is static. Based on the thermodynamic parameters, hydrophobic interaction and hydrogen bonding were found to be involved in the formulation of complexes in the BSA-IPM system. As Gibb’s free energy change was negative, the interaction was a spontaneous process for the BSA-IPM system at both temperatures (298K and 308K). Binding constants (K) and the number of binding sites (n) were determined at different temperatures (298K and 308K). Based on the findings from the experiment regarding the interaction of BSA-IPM, the drug-protein binding mole ratio is 1:1 at temperatures 298K and 308K. The binding process is reversible and spontaneous.