Conversion of Quinine Derivatives into Biologically Active Ionic Liquids: Advantages, Multifunctionality, and Perspectives

In this study, we demonstrate that quinine with confirmed antiviral and antifeedant activity can be derivatized and formulated as multifunctional ionic liquids which allow one to tune their biological, chemical, and physical properties. Following the optimization of quinine alkylation, pure 1-alkylquinine bromides with alkyl chain length ranging from ethyl to dodecyl were synthesized and extensively characterized. In the next step, these derivatives were combined with counterions of natural origin, which resulted in the formation of naturally derived ionic liquids. Our results indicate that the transformation of quinine into ionic liquids may improve antifeedant properties by 265% compared to the activity of quinine-free base. Moreover, unlike the majority of known cases, the reduction of the alkyl chain length results in a significant increase in this type of biological activity.