High voltage electrical discharge-assisted extraction of bioactive compounds from red onion peel (Allium cepa L.) using natural deep eutectic solvents: Efficiency, stability, and functional properties

• Citric acid: glycerol NADES maximized the recovery of bioactive compounds. • HVED intensified the NADES-assisted extraction of anthocyanins and phenolics. • NADES-based extract had 20 % more antioxidant activity than the ethanolic extract. • NADES could increase the half-life time and storage stability of anthocyanins. • The stability of anthocyanins in NADES was 2-fold higher than in ethanol at pH 7. The green extraction of bioactive compounds from red onion peel ( Allium cepa L.) using high voltage electrical discharge (HVED) technique coupled with natural deep eutectic solvents (NADESs) was investigated. Seven NADESs with various molar ratios were evaluated based on the extraction efficiencies of anthocyanins and polyphenols. Red onion peels were first pretreated under the optimal HVED conditions, and then, solid-liquid extraction was done using the selected NADES. The optimal processing parameters for HVED treatment were a voltage of 120 V and a pulse number of 20. Moreover, the optimal NADES-assisted extraction was performed using citric acid: glycerol (Cit: Gly) with a solvent-to-water ratio of 75:25, a liquid-solid ratio of 10:1 mL/g, and a stirring temperature of 40 °C for 60 min. A combination of HVED treatment with NADES extraction recovered 1.3-, 1.2-, and 1.8-fold more anthocyanin, polyphenol, and flavonoid contents, respectively, compared to ethanol. Also, the antioxidant property of the NADES-based extract was 20 % more than that of the ethanolic one. Notably, the reduced degradation kinetics, increased half-life time, and extended storage time of anthocyanins in Cit: Gly showed the superiority of NADESs in the extraction procedure over conventional solvents, which could find advantageous utilizations in the food and pharmaceutical industries.