Green extraction of phenolic compounds from strawberry waste based on natural deep eutectic solvents

Abstract

The increase in ecological sensitivity and the interest in ‘green chemistry’ are leading to a decrease in the use of environmentally harmful substances in chemical processes. Replacing traditional solvents with NaDES (Natural Deep Eutectic Solvents) is an excellent green alternative to extract bioactive compounds from agri-food industry wastes, as these solvents bring numerous advantages and are environmentally friendly. In this work, the performance of traditional organic solvents and NaDES were compared for the extraction of phenolic compounds (PCs), with different physicochemical characteristics, from strawberry residues. For this reason, numerous combinations of NaDES have been evaluated, optimising the experimental conditions of the process. The samples were analysed using HPLC–MS/MS, which allowed the identification and quantification of numerous PCs in the samples. The best extraction efficiencies were obtained using choline chloride (ChCl) as hydrogen bond acceptor and lactic acid (LA) as hydrogen bond donor, in a ratio of 1:5 and containing 30% of water. Isoquercetin, hesperidin and catechin were the phenolic compounds most remarkable in samples, with a content of ca. 43%, 26% and 11% of total polyphenols, respectively. Finally, the evaluation of the method through the Analytical GREEness calculator showed how NaDES can satisfactorily replace traditional extractions with a great performance and reduced impact on the environment.