OBTAINING READY-TO-USE ANTIOXIDANT EXTRACTS FROM WINEMAKING BY-PRODUCTS USING NATURAL DEEP EUTECTIC SOLVENTS (NADES)

The wine industry generates various by-products rich in bioactive compounds, such as grape pomace and wine lees. Often discarded, these materials represent a strategic opportunity for the development of sustainable functional ingredients. In this study, the application of natural deep eutectic solvents (NADES) based on choline chloride and citric acid (1:1, m/m, 50% water) was investigated both as extraction media and as multifunctional systems for obtaining ready-to-use winery extracts. Samples of grape pomace (skin and seed) and wine lees were dried in a forced-air oven at 45 °C, ground in a knife mill, and sieved to standardize particle size (32 mesh). Extraction was carried out by maceration at 50 °C with a solid-to-solvent (NADES) ratio of 1:30 (m/v) for 60 minutes. After centrifugation and filtration, the extracts were evaluated for antioxidant activity using DPPH (517 nm), ABTS (734 nm), and ORAC (excitation λ 485 nm; emission λ 520 nm) assays, with measurements performed in a microplate reader (Multileader Infinite M200, TECAN, Switzerland). Results were expressed as μmol Trolox equivalents per mL. Grape seeds exhibited the highest antioxidant activity values according to the DPPH (657.53 μmol TE/mL) and ABTS (791.81 μmol TE/mL) methods, whereas grape skins stood out in the ORAC assay (978.45 μmol TE/mL) and also displayed expressive antioxidant values in the DPPH (588.02 μmol TE/mL) and ABTS (762.87 μmol TE/mL) methods. Wine lees also demonstrated relevant bioactive potential, with values ranging from 381.94 to 562.83 μmol TE/mL for DPPH and ORAC, respectively. The responses of the different methods varied according to the analyzed matrix, with each by-product showing superior performance in distinct assays, reflecting the diversity of phenolic composition and the chemical structure of the compounds present. This highlights that the effectiveness of each method may vary depending on the type and distribution of bioactive compounds in each by-product. It is important to emphasize that, regardless of the method employed, the extracts obtained with choline chloride–citric acid-based solvent exhibited high antioxidant activity, demonstrating the efficiency of the solvent in extracting natural antioxidants, thus enabling the direct use of the extracts in different food, cosmetic, or pharmaceutical applications. It can be concluded that all evaluated winery by-products possess bioactive potential, with grape seeds standing out as the matrix with the highest antioxidant capacity. The use of NADES represents a viable, innovative, and environmentally responsible strategy.