Green next-generation excipients enriched in polyphenols from recovery of grape processing waste black bentonite: Influence of unconventional extraction solvents on antioxidant properties and composition

According to the UN Agenda 2030, several actions could be taken to act synergistically towards various areas of critical importance for both the humanity and the planet. Among them, the application of a circular economy model based on the valorisation of the wastes from the local resources could be a virtuous attitude. In this view, this work proposes a dual green approach for recovery of the waste black bentonite from the fining of organic white grape must. Indeed, this virtuous recovery idea is enhanced by the choice of both eco-friendly extraction method (maceration) and solvents. The latter were unconventional solvents selected among the pharmaceutic/cosmetic liquid hydrophilic excipients (waste-to-market approach) characterized by safety and high solvent power toward polyphenols. PEGs (200, 400, 600), Propylene Glycol and Glycerol were tested and the extracted compared by HPLC-DAD analyses as well as the Folin-Ciocalteu, DPPH and Bradford assays. PEG200 emerged as the best one, leading to coloured extract containing great amount of polyphenols (3.123 ± 0.106 mg/g) and specifically Quercetin (60.778 ± 2.307 μg/mL), which confer it interesting scavenger properties, potentially making it directly useful in a wide range of fields from the pharmaceutic to the cosmetic ones.