Interactions between components of choline chloride/propylene glycol or ethylene glycol deep eutectic solvents in the presence of water by determination of amlodipine besylate solubility profile

Abstract

Improving amlodipine besylate (AMB) solubility as a poorly water-soluble drug is one of the biggest limits in preparation of different formulations in the pharmaceutical industry. Aiming to increase the aqueous AMB solubility, its solubility in choline chloride/propylene glycol (ChCl/PG) or choline chloride/ethylene glycol (ChCl/EG) deep eutectic solvents (DESs)-water mixtures was determined here using a shake-flask way at 293.2 K–313.2 K and ambient pressure (≈85 kPa) and correlated by models of van't Hoff, Jouyban-Acree and Jouyban-Acree-van't Hoff. In these mixtures, the maximum molarities of AMB (0.297 and 0.150 mol L−1) were determined at 313.15 K when the mass fraction of ChCl/PG and ChCl/EG were 0.8 and 1.0. The maximum AMB solubility in water was (0.008 mol L−1) at 313.15 K and observed an increment of 36.7-fold and 18.5-fold in ChCl/PG + water and ChCl/EG + water, respectively. The water effect on the stability of ChCl-PG or EG hydrogen bonding interactions was investigated by measuring the molarity of AMB in ternary mixtures of ChCl + PG or EG + water at 298.15 K. Comparing the obtained results for the above-mentioned binary and ternary mixtures presented that there is no real binary mixtures of DES and water when the water mass fraction was between 0.9 to 0.4 for ChCl/PG and 0.9 to 0.2 for ChCl/EG DESs, respectively. From correlation of AMB solubility with the selected cosolvency models, the mean percentage deviations were obtained between 3.4 % to 12.3 % which are on the acceptable range. Moreover, the consequences of apparent thermodynamic analysis demonstrated an endothermic and entropy-driven dissolution of AMB in all portions of ChCl/PG or ChCl/EG + water pseudo-binary mixtures.