Natural deep eutectic solvents and ultrasound-assisted extraction: Green approaches for extraction of wine lees anthocyanins

To establish environmentally friendly extraction methods for the anthocyanins in wine lees, natural deep eutectic solvents (NADES) were investigated as a green alternative to conventional solvents, coupled with high-efficiency ultrasound-assisted extraction. Screening for the optimal NADES for this extraction was initially performed. A choline-chloride-based NADES with malic acid as the hydrogen bond donor was selected as the most promising, which provided more effective extraction of wine lees anthocyanins compared to a conventional solvent. To optimise this extraction of wine lees anthocyanins using the NADES and ultrasound-assisted extraction, response surface methodology was successfully applied. Considering the maximum amount of extracted compounds, the optimal conditions were: extraction time, 30.6 min; ultrasound power, 341.5 W; and water content in NADES, 35.4% (w/w). This approach using NADES as a green solvent and ultrasound as an alternative energy source represents a good choice for designing eco-friendly extraction methods for phenolic compounds from various sources.