Phenolic compounds, such as ferulic, caffeic and p-coumaric acids and rutin, are commonly present in natural resources, for example plants (e.g. eggplant), cereals (e.g. rice), vegetables (e.g. beans) and fruits (e.g. oranges). Several studies have already demonstrated their potential on the pharmaceutical and cosmetic fields, as antioxidant, anti-inflammatory and anticancer. However, these compounds have a low aqueous solubility, restricting their applicability.

Ionic liquids (ILs) can act as multifunctional excipients, namely, to enhance drug solubility and incorporation into various delivery systems.

In this work six ILs containing natural amino acids, (2-hydroxyethyl)trimethylammonium phenylalaninate [Cho][Phe], (2-hydroxyethyl)trimethylammonium glycinate [Cho][Gly], 1-ethyl-3-methylimidazolium phenylalaninate [Emim][Phe], 1-ethyl-3-methylimidazolium glycinate [Emim][Gly], 1-butyl-3-methylimidazolium phenylalaninate [Bmim][Phe] and 1-butyl-3-methylimidazolium glycinate [Bmim][Gly], were prepared and their impact on the incorporation of the four phenolic compounds, in O/W emulsions, was evaluated.

The use of ILs allowed the incorporation of higher amounts of the studied drugs, since their solubility was enhanced. They also led to more viscous emulsions, improving the stability of the formulations.