Natural deep eutectic solvents characteristics determine their extracting and protective power on chlorogenic acids from sunflower meal

Sunflower meal is a residue of the edible oil extraction and a promising source for the extraction of phenolic compounds, especially the chlorogenic acid (CGA) family. Their clean extraction and later conservation may be improved by the use of natural deep eutectic solvents (NaDES). This study evaluated the extraction and stability of phenolic compounds from sunflower meal using different formulations of NaDES as extractor, in contrast to ethanol (40%). The main goal was to find a clean extraction method for this rich bioactive compound by-product that would also enhance its stability and bioactivity. The best solvent was the NaDES formulated with lactic acid:glucose (LA:G - 5:1) that resulted in an extract containing 1786 mg CGA per liter of extract, followed by ethanol 40% (1305 mg.L−1) and choline chloride:glycerol (807 mg.L−1). The results for the antioxidant activity of the extracts did not follow the results for chlorogenic acid concentration, as they were higher in the ethanolic extract (102.59 and 90.35 mg/100g - ABTS and DPPH, respectively) than in the NaDES extracts (83. 36 and 66.56 mg/100g for LA:G and 48.26 and 26.17 mg/100g for CC:GL). In terms of stability, the acidic NaDES (LA:G) showed better protection against heat treatment (60 °C) and storage (30 days), while ethanol exhibited better stability under light exposure (7 days). The findings suggest that the NaDES composition, pH and other characteristics may influence both, extraction efficiency, antioxidant activity and stability, enabling the clean extraction and stabilization of phytochemicals from agro-industrial waste.