Methods for Extraction of Bioactive Compounds from Plant and Animal Matter Using Deep Eutectic Solvents

Nowadays, scientists are going through developing more eco-friendly analysis methods of simple and complex samples that follow the principles of “green chemistry.” One of the followed strategies is by replacing the toxic conventional organic solvents used in the extraction by a new generation of solvents called “deep eutectic solvent” or “natural deep eutectic solvent.” These solvents are formed between two or more cheap nontoxic components via hydrogen bonds. This review presents the various extraction methods that use deep eutectic solvents as extraction solvents, mainly the liquid-liquid-phase microextraction methods, solid-phase microextraction methods, and the newly combined techniques. In addition, the advantages and drawbacks of using these green solvents in comparison to the conventional organic solvents used in conventional extraction methods are discussed. It was observed that, with all reported extractions, deep eutectic solvents showed better extraction efficiency and higher recovery values for the studied natural target analytes compared to water and lots of conventional organic solvents. For the protein extraction, these solvents showed around 93–99% extraction efficiency. In addition, new types of deep eutectic solvents, like the ternary deep eutectic solvent molecularly imprinted polymer, were synthesized, improving the solvent characteristics; therefore, lower volume of the solvent was used with shorter extraction time.