Influence of antidepressant clomipramine hydrochloride drug on human serum albumin: Spectroscopic study Malik Abdul Rub a,b, ⁎, Javed Masood Khan c , Naved Azum a,b , Abdullah M. Asiri a,b a Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia b Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah 21589, Saudi Arabia c Department of Food Science and Nutrition, Faculty of Food and Agricultural Sciences, King Saud University, 2460, Riyadh 11451, Saudi Arabia abstract article info Article history: Received 26 March 2017 Received in revised form 16 May 2017 Accepted 31 May 2017 Available online 01 June 2017 The interactions of serum albumins with a variety of drugs have expected immense interest currently owing to their considerable achieve in the biomedical area. In the current study, we have accounted the interactions be- tween clomipramine hydrochloride (CLP) drug and human serum albumin (HSA) using various techniques such as UV-visible, fluorescence as well as circular dichroism (CD) at different temperatures (298.15, 310.15 and 318.15 K). CLP is a tricyclic antidepressant which is used to treat obsessive compulsive disorder. The out- comes of the current examination under the physiological circumstances suggested a static type of binding takes place between the CLP and HSA having binding constants of 10 4 L/mol. The evaluated thermodynamic pa- rameters, inferred that reaction was an endothermic and spontaneous process, and hydrophobic together with electrostatic interactions are the main binding forces engaged in the formation of the HSA-CLP complex. Accord- ing to Förster's theory, the distance (r 0 ) between donor and acceptor was achieved to be 3.09 nm. The count of binding sites for binding of CLP on HSA was obtained to be around one. Adding of CLP causes the quenching of HSA fluorescence and a red shift at both excitation wavelengths (280 and 295 nm) owing to the hydrophobic in- teraction between drug and HSA. Circular dichroism (CD) spectra of HSA confirmed considerable alteration in the conformation of protein structure in the attendance of CLP. Therefore, the results obtained herein will be of bio- logical importance in pharmacology as well as clinical medicine. © 2017 Elsevier B.V. All rights reserved. Keywords: Clomipramine hydrochloride Human serum albumin Fluorescence Binding constants Enthalpy change 1. Introduction The nature and types of interaction between small molecules and biomacromolecules characterize an active area of research. There are two most important fundamental aspects of protein (biomacromolecules) behavior are folding and binding. The actual function of a protein is usually feasible simply when it is folded into a particular three-dimensional conformity. The circulations, free concen- tration as well as the metabolism of a variety of drugs are powerfully influenced by drug–protein interactions in human being [1–5]. These types interaction can also regulate the drug stability as well as toxicity for the duration of the chemotherapeutic course of action [1]. Numerous drugs (hydrophobic as well as hydrophilic) work out their action through interaction by biological membranes. The researches on the interactions of drug particles through a variety of proteins obtain significant concern in the area of chemistry, life science in addition to clinical medicine from last many years. The mode and the extent of these interactions control the biosafety, pharmacological action, delivery time, remedial effectiveness as well as the layout of drugs. Therefore, examinations of these interactions assist inconsiderate the structural characteristics crucial for the bio-affection of a range of medicines on the way to the pharmacological action [6–8]. Physically powerful binding reduces the amount of free drug in the blood, while feeble binding causes a poor distribution time. The information of serum albumin and drug interaction is able to assist us healthier recognize the absorption and circulation of the drug. Serum albumins play a critical role in the drug delivery because it is the ultimate form for examines the interactions of drug-protein in vitro. Human serum albumin (HSA) is a large amount plentiful soluble protein (nearly 56% of whole protein), subsequently globulins (37%) and fibrin- ogen (6%) takes part in the significant responsibilities in carrying of macromolecules as well as upkeep of osmotic pressure [9,10]. HSA has a distinct peptide progression of 585 amino acids. It is self-possessed of three structurally akin domains (I, II and III), all holding two sub do- mains (A and B), sustained by seventeen disulfide bridges [11]. HSA can bind with various substrates, counting metal, amino acids, fatty acids as well as different drugs. They bring a significant function in the carry as well as the discharge of a range of endogenous together with an exogenous constituent in blood [12] owing to the being of a restricted quantity of binding sites of extremely diverse accuracy [13]. Journal of Molecular Liquids 241 (2017) 91–98 ⁎ Corresponding author at: Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia. E-mail address: aabdalrab@kau.edu.sa (M.A. Rub). http://dx.doi.org/10.1016/j.molliq.2017.05.143 0167-7322/© 2017 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq