Green extraction of oat saponins based on deep eutectic solvents

With the advent of new-generation green extraction solvents, deep eutectic solvents (DESs) present significant prospects for the extraction of bioactive substances. In this study, saponins were extracted from oats using an ultrasonic-assisted method with green DESs, replacing conventional toxic organic solvents. Adding sodium chloride markedly reduced solubility, resulting in the separation of two phases from the extract: DES and water. The saponins were separated into the water phase, while the DES was reused in subsequent extractions, supporting extractant recycling and promoting sustainable development. Adding salt offers a more gentle, convenient, and cost-effective alternative to current phase separation methods, such as pH adjustment, temperature variation, and carbon dioxide or nitrogen gas application. Optimizing the extraction and recovery parameters yielded the highest oat saponin extraction efficiency at 18.73 mg g –1 , and the recovery was 86.4 %. When compared with ethanol extracts, DES extracts exhibited superior antioxidant activity. Lastly, the greenness of this extraction method was confirmed through three greenness evaluation programs of greenness. The extraction method based on emerging responsive solvents can be extended to other hydrophilic bioactive substances.