Grape pomace as a valuable source of nutraceuticals in Deep Eutectic Solvents ready-to-use extracts

Agro-industrial waste represents one of the main causes of global environmental pollution. For this reason, the valorization of these by-products through their reuse as sources of bioactive compounds is a challenging aim of research and industry. In this work, two varieties of grape pomace (Cabernet Sauvignon and Petit Verdot) were selected for solid-liquid extraction with employment of deep eutectic solvents (DESs) as sustainable green media, using hydroalcoholic solutions as references. Extracts obtained from both fresh and dried grape pomaces were chemically characterized for their phenolic profiles through HPLC-DAD, and eight out of fifteen phenolic compounds, selected as standards, were detected and quantified. The antioxidant activity of the extracts was evaluated in vitro through the DPPH photometric assay. Choline Chloride/Urea (1:4 mol/mol + 40% water) extracts have been the most promising in this regard. Moreover, our extracts exhibited good antibacterial activities, in particular for the Betaine/Lactic acid (1:4 mol/mol + 40% water) DES ones. Starting from this evidence, seventeen different red and white grape pomaces were then extracted with four previously selected DESs and the phenolic profile of the resulting extracts was again characterized by HPLC-DAD. The samples with the most promising bioactivity, namely Merlot and Sangiovese extracted with Betaine/Lactic Acid (1:4 mol/mol + 40% water) and Choline Chloride/Ascorbic Acid (2:1 mol/mol + 40% water), were additionally characterized by LC-ESI-TOF-MS, while bioavailability and antimicrobial studies are now ongoing, with the final aim to employ these products as ready-to-use food and/or feed supplements.