LAUSR

Low-transition temperature mixtures (LTTMs), also known as deep eutectic solvents, are liquid mixtures of natural substances that possess unique properties, not encountered with conventional solvents. Such liquids represent a state-of-the-art means of extracting bioactive plant constituents, yet the plethora of combinations of various substances that form LTTMs dictates detailed comparative testing, to identify LTTMs with high extraction capacity. In this study, a number of combinations of hydrogen bond donors (HBDs) with sodium acetate serving as the hydrogen bond acceptor (HBA), was attempted. The stable LTTMs formed were then used to extract antioxidant polyphenols and pigments from red grape pomace (RGP). The LTTM composed of L-lactic acid and sodium acetate at a molar ratio of 5:1 was found to be the most efficient solvent, giving a total polyphenol yield of 134.54 mg gallic acid equivalents per g of dry weight and a total pigment yield of 3.32 mg malvin equivalents per g of dry weight. The extract obtained with this particular LTTM also possessed the strongest antioxidant activity. The principal compounds in this extract were tentatively identified as phenolic acids, anthocyanin pigment derivatives and a flavonol glycoside.