Aqueous Solutions of Surface-Active Ionic Liquids: Remarkable Alternative Solvents To Improve the Solubility of Triterpenic Acids and Their Extraction from Biomass

Triterpenic acids (TTAs) are well-known for their relevant biological properties and have been facing an increasing interest for nutraceutical and pharmaceutical applications. To overcome the concerns associated with the commonly used volatile organic solvents for their extraction from biomass, here we investigate the potential of aqueous solutions of ionic liquids (ILs) as alternative solvents. The solubility of ursolic acid (UA) was first determined in several aqueous solutions of ILs (hydrotropes or surface-active) at 30 °C for evaluation of the dissolution phenomenon. Conventional surfactants were also investigated for comparison purposes. The collected data reveal a remarkable enhancement in the solubility of UA (8 orders of magnitude) in surface-active IL aqueous solutions when compared to that in pure water. Afterward, the potential of these IL aqueous solutions was confirmed by their use in the extraction of TTAs from apple peels. Total extraction yields of TTAs of 2.62 wt % were obtained using aqueous solutions of surface-active ILs at moderate conditions, overwhelming the extraction yields of 2.48 wt % obtained with chloroform and 1.37 wt % with acetone using similar conditions.