Solubility of biological compounds in amino acid ionic liquids and the role of anion and cation in dissolution: Molecular dynamics simulations

The solubility of the bioactive compound carvacrol (CAR) was investigated using ۵ amino acid ionic liquids (AAILs). In this study, the linear tetraethylammonium cation ([N۲۲۲۲]) and the cyclic ۱-propyl-۳-methylimidazolium cation ([PMIM]) were used. Then, by adding three functional groups, amine (NH۲), carboxyl (COOH), and hydroxyl (OH), the role of the functional group in the dissolution of CAR was observed. The anion of all ۵ solvents is glycinate (GLY). The potential of mean force (PMF) diagram shows that all ۵ AAILs have the ability to dissolve CAR. The results of the radial distribution function (RDF) show that in all AAILs, the anion-CAR interaction is stronger than the cation-CAR interaction. Although initially the anion-CAR interaction strength in the [N۲۲۲۲][GLY] system was greater than that in [PMIM][GLY], by adding a functional group to the [PMIM] cation, we observed an increase in the anion-CAR interaction strength in solvents containing the cyclic imidazolium (IM) cation, with the NH۲ functional group being more successful than the other two functional groups.