Menthol-based Eutectic Mixtures: Hydrophobic Low Viscosity Solvents

Inspired by one of the major problems in the pharmaceutical industry, we advantageously used the formation of eutectic mixtures to synthesize new solvents. The aim of this work is to identify low viscosity, cheap, biodegradable and hydrophobic eutectic solvents from natural resources. Consequently, novel eutectic mixtures based on dl-menthol and naturally occurring acids, namely pyruvic acid, acetic acid, l-lactic acid, and lauric acid, were synthesized and are here reported for the first time. The obtained dl-menthol-based eutectic mixtures were analyzed using NMR and FTIR spectroscopy in order to check their structures and purities and to confirm the interaction of the two compounds leading to the eutectic formation. Important solvent thermophysical properties, such as density and viscosity, of the prepared eutectic solvents with different water contents (dried and water-saturated) were measured. Finally, taking advantage of their hydrophobic character, namely the formation of two phases with water at room temperature, four different biomolecules, caffeine, tryptophan, isophthalic acid, and vanillin, were extracted and the extraction efficiencies of the prepared eutectic solvents compared.