Natural deep eutectic solvents (NaDES) as an emerging technology for the valorisation of natural products and agro-food residues: a review

A review paper on the natural deep eutectic solvents (NaDES) application to the extraction of bioactives from natural products and agri-food wastes is introduced. NaDES are eutectic mixtures of two or more natural compounds forming a liquid phase at room temperature based in hydrogen bond acceptors (quaternary amines, alcohols) and hydrogen bond donors (sugars, organic acids). NADES have unique properties such as low toxicity, biodegradability and high solubility for a wide range of compounds. They represent a sustainable alternative to traditional organic solvents in a variety of applications, particularly metabolites extraction. Therefore, the status of NaDES is displayed in terms of their inspiration in nature, their preparation and physicochemical properties, as well as the extraction conditions for biologically important phytochemicals such as alkaloids, carotenoids, and phenolics (anthocyanins, isoflavonoids, and curcuminoids). Remarks on emerging technologies as well on therapeutic, hydrophilic, and hydrophobic NaDES systems are inserted. As NaDES can be easily prepared from natural and renewable sources, they are a promising green alternative in the food, nutraceutical, and pharmaceutical industries.