Choline-amino acid ionic liquids as green functional excipients to enhance drug solubility

The development of effective forms to incorporate poorly soluble drugs into delivery systems remains a problem. Thus, it is important to find alternatives such as finding excipients that increase drug solubility. Ionic liquids (ILs), particularly choline-based ILs, have been studied as solubility enhancers in drug delivery systems. Nonetheless, to acknowledge this property as a functionality, it needs to be proven at non-toxic concentrations. Hence, herein two choline-amino acid ILs were studied as functional excipients by evaluating their influence on the solubility of the poorly water-soluble ferulic acid and rutin, while considering their safety. The solubility of the drugs was always higher in the presence of the ILs than in water. Ionic liquids did not affect the radical scavenging activity of the drugs or the cell viability. Moreover, stable oil-in-water (O/W) emulsions were prepared containing each drug and the ILs, allowing a significantly higher drug loading. Globally, our results suggest that choline-based ILs may act as green functional excipients, since at non-toxic concentrations they considerably improve drug solubility/loading, without influencing the antioxidant activity of the drugs, the cell viability, or the stability of the formulations.