Screening of ionic liquids for the solubility enhancement of quinine using COSMO-RS

Abstract

Quinine has traditionally been used in medicine to treat parasitic disease malaria due to its antimalarial activities. It is sparingly soluble in water and highly soluble in organic solvents. However, these solvents are not environmentally friendly, so greener solvents need to be explored and designed. Ionic liquids (ILs) were successfully observed to be greener and capable of dissolving biologically active compounds. However, finding a potential IL from millions of possible IL combinations is challenging. This work utilizes the conductor-like screening model for real solvents (COSMO-RS) to address this issue. This study aims to determine the dissolution behavior of quinine in ILs employing the COSMO-RS. A total of 540 IL combinations of 9 cations and 60 anions were investigated. The efficacy of each IL was evaluated by predicting the activity coefficients at infinite dilution, solvation-free energy, selectivity, capacity, and performance index (P.I.). This study reveals that ILs with shorter alkyl chains, polar and non-aromatic characteristics, and smaller anions are advantageous for the solubility enhancement ofquinine.The most effective ILs, choline acetate, choline glycinate, and choline threoninate, displayed the highest selectivity, capacity, P.I., and lowest activity coefficient and solvation-free energies. The findings of the current study unlock key insights into the solubility behaviour of quinine in an aqueous solution employing ILs.