Solvation behaviour of biologically active compounds in aqueous solutions of antibacterial drug amoxicillin at different temperatures

The interactions of glycine (Gly), L-alanine (Ala), L-valine (Val) and L-Leucine (Leu) with drug amoxicillin (AMX) as a function of temperature have been investigated by combination of volumetric and acoustic measurements. Densities and speeds of sound of amino acids in aqueous solutions of amoxicillin have been measured at T = (305.15, 310.15 and 315.15) K and atmospheric pressure. The apparent molar volume (V-phi(0)), the partial molar volume (V-phi(0)) and standard partial molar volumes of transfer (DV phi 0) for amino acids from water to aqueous amoxicillin solutions have been calculated from density data. Group contributions of amino acids to partial molar volume were determined. Partial molar isentropic compression (K-phi,K-s) and partial molar isentropic compression of transfer (Delta K-phi,s(0)) have been calculated from speed of sound data. The pair and triplet interaction coefficient have been calculated from both the properties. The results have been explained based on competing patterns of interactions of co-solvents and the solute. (C) 2014 Elsevier Ltd. All rights reserved.