Drug−Amino Acid Interactions in Aqueous Medium: Volumetric, Compressibility, and Viscometric Studies

Abstract

Density (ρ), speed of sound (u), and viscosity (η) measurements of amino acids l-glutamine and l-histidine in aqueous solutions of metformin hydrochloride (an antidiabetic drug) (0.01, 0.07, and 0.13 mol·kg–1) were carried out in the concentration range (0.02–0.20 mol·kg–1) at 293.15, 298.15, 303.15, 308.15, and 313.15 K. The experimental data has been meticulously used to enumerate various parameters which assist to procure valuable information regarding the presence of different kinds of intermolecular interactions present in the ternary (metformin hydrochloride + water + amino acids) system. The results were interpreted in terms of various metformin hydrochloride–amino acid intermolecular interactions through a cosphere overlap model. The ion–ion interactions are the key players in ternary system and these interactions are of higher order in the case of histidine as compared to glutamine. Also application of transition state theory has been made to calculate the thermodynamic activation parameters for ...