The role of hydrogen bonding in solubilizing camptothecin in hydrophilic and hydrophobic ionic liquids

Abstract

Utilizing ionic liquid (IL)-water mixtures as selective extraction solvents for raw materials from natural sources represents an efficacious approach; however, elucidating the underlying mechanisms inherent in various types of IL-aqueous solutions continues to pose a significant challenge. In this study, molecular dynamics simulations and density functional theory calculations are employed to illuminate the influence of the functional anion within ILs and the water content on the solvation mechanism and phase separation phenomena observed during the extraction of camptothecin (CPT) using aqueous IL solutions. The simulation results show that the anions in ILs preferentially dissolve CPT through hydrogen bonding at low water concentrations. As the water concentration increases, the hydrophobic IL binds more tightly to CPT, enabling the water to self-aggregate. The anions in hydrophilic IL form hydrogen bonds with water instead, further enhancing the dissolution of CPT. This work reveals the mechanism of phase separation and solvation of different types of IL aqueous solutions, which is helpful in developing new drug extraction and purification technologies.