Carmen Terán, Marta María Mato, Pedro Besada
Ionic liquids (ILs) derived from bioactive compounds have emerged as a versatile and highly tunable platform for designing novel functional materials with biomedical applications. Many of these systems incorporate naturally occurring carboxylate anions of relevance to medicinal chemistry, biotechnology, and biomedicine, which has intensified interest in this family of bioinspired ILs. This review focuses on ILs derived from carboxylic acids of natural origin, including fatty acids, phenolic acids, and hydroxy acids, and highlights recent advances in their design, bioactivity, and physicochemical characterization, with particular emphasis on systems based on biocompatible components. Additionally, it addresses synthetic strategies, toxicological aspects, and biological potential. Key physicochemical properties discussed include thermal stability, glass transition temperatures, melting and crystallization points, viscosity, density, solubility, refractive index, polarity, and amphiphilic behavior.