Abstract
This study investigates novel approaches for the green extraction of polyphenols from grape pomace. Sixteen natural deep eutectic solvents (NADES) systems, based on either choline chloride or sucrose as hydrogen bond acceptors (HBAs) and one of tartaric, malic, lactic, oxalic, or citric acids, or 1,2-propylene glycol as hydrogen bond donors (HBDs), were evaluated. Response surface methodology (RSM) was applied to optimize the extraction parameters, namely water content and extraction time, for maximizing total anthocyanins and total flavonols content using different combinations of choline chloride and lactic acid. Optimal conditions were found to be not more than 25% (v/v) of water and an extraction ratio of 30 mL/g dw. Overall assessment of the results pointed at the system ChCl:lactic acid, 1:2 containing 25% water (CL25) as a satisfactory compromise alternative for both anthocyanin and flavonol extractions. Nevertheless, marked differences were found in the affinity of different NADES towards distinct phenolic compounds, which could be exploited for the rational selection of the most suitable solvent depending on the phenolic profile of the matrix or when searching for particular target compounds. In addition, the extracts obtained with distinct NADES showed notable antioxidant activity and, unlike conventional methanolic extracts, also exhibited antimicrobial effects attributable to the extraction solvent itself, highlighting their potential for food-related applications.