Influence of two choline-based ionic liquids on the solubility of caffeine

Poor drug solubility represents a major problem for the development of new drug delivery systems. Finding new excipients that promote drug solubility is one of the strategies currently used. In this context, ionic liquids (ILs) have been studied as solubility promoters due to their ability to be placed in either lipophilic or hydrophilic solutions. Two choline-based ILs, [Cho][Met] and [Cho][Cys], were prepared and their influence on the solubility of a model hydrophilic drug, caffeine, was evaluated at 25 oC. Results show that both ILs improved drug solubility, with [Cho][Met] providing a higher soluble concentration. Our results suggest that the studied choline-based ILs are effective solubility enhancers of caffeine and thus may potentially be used as functional ingredients in drug delivery systems.