Multi spectroscopic study of diltiazem interaction with human serum albumin

The binding of a drug to albumin is a major determinant of its pharmacokinetic and pharmacodynamic profile[1, 2]. In addition albumin is a well-known delivery protein in the body and in drug formulation. Diltiazem hydrochloride (DLT) is a calcium channel blocker which widely used in many cardiovascular diseases, especially coronary heart disease and hypertension[3, 4]. Study of diltiazem interaction mechanism with human serum albumin (HSA) can provide useful information for clinical and research purposes.The UV-Vis spectrum of HSA, Diltiazem and HSA-Diltiazem were recorded at room temperature (298K) using a Shimadzu2550 UV/VIS Spectrophotometer (Japan) equipped with 3.0 cm quartz cells. Flourometric were recorded using Cytation 5 (BioTek,USA).The spectra were studied in the range of 200-500 nm by exciting at 278 nm. The quenching data were analyzed using the Stern-Volmer equation in order to get information about binding site and binding constant.UV-Vis absorption of HSA enhanced at 278 nm regularly by the increasing concentration of diltiazem which could be regarded as a change in the Trp microenvironment of the HSA due to complex formation. The stern volmer constant of the flourimetric quenching of the HSA emission at 340 nm was 1.495(M-1)×104 with an intercept of 0.9819 which is an indicative of a 1:1 interaction. A blue shift of the emission wavelength showed that increase in the hydrophobicity of the microenvironment around the tryptophan residues.the logarithmic analysis of the quenching data revealed that the binding constant is 10.76(M-1)×104 and the number of binding sites are 1.2109 . the rate constant of 0.0014(M-1)×104 showed a dynamic mechanism of interaction.