Smart advanced solvents for bioactive compounds recovery from agri-food by-products: A review

Background: Worldwide, huge amounts of by-products and wastes are generated in agri-food sector annually. This biomass is usually discarded provoking serious environmental problems. However, these residues represent an excellent source of bioactive compounds so that their exploitation can be considered as a promising possibility from an economic and environmental perspective. Conventional extraction technologies using organic solvents have been employed to recover high-value molecules showing several drawbacks such as toxicity, high volatility and non-renewability. Therefore, the search of alternative green solvents for the extraction of bioactives and in order to reduce the environmental impact and to achieve a widespread consumer acceptance is mandatory. Recently, deep eutectic solvents (DESs) and natural deep eutectic solvents (NaDESs) have received great attention for their physicochemical features for bioactive compounds extraction. Scope and approach: This review describes the state of the art of the applications of DESs and NaDESs in the field of the revalorization of agri-food by-products to obtain and isolate bioactive compounds. The synthesis and properties of these avant-garde solvents are described. In particular, the main bioactives extracted using DESs and NaDESs from several residues from citrus, winemaking, olive oil production, onion, seaweeds, animal and fish industries were systematically reviewed and collected. Key findings and conclusions: DESs and NaDESs combined with emerging technologies to recover biomolecules from agri-food by-products show promising results in comparison with traditional methods of extraction using conventional solvents. These emerging solvents present advantages which make them good candidates for being implemented by the industry, considering their low toxicity, recyclability, tunable properties and environmentally friendly. Therefore, this new generation of solvents opens new options in the field of recovering bioactive compounds from agri-food by-products.