Ultrasound-assisted natural deep eutectic solvent extraction of anthocyanin from Vitis davidii Foex. pomace: Optimization, identification, antioxidant activity and stability

An efficient and environmentally friendly extraction method utilizing an ultrasonic-assisted natural deep eutectic solvent (UAE-NADES) was developed for the extraction of anthocyanins from Vitis davidii Foex. A screening process was conducted to evaluate seven different NADESs, resulting in the selection of a high-efficiency NADES (choline chloride-glycerol (ChGly)). To analyze the influence of significant factors and their interactive effects on the total anthocyanin content (TAC), response surface methodology (RSM) was employed. Furthermore, the conditions of extraction were optimized to attain the most productive yield of total anthocyanin content. The theoretical optimal conditions were determined to be a liquid‒solid ratio of 34.46 mL/g, an extraction temperature of 322.79 K and an ultrasonic power of 431.67 W, under which the verification TAC value (3.682 ± 0.051 mg/g) was highly consistent with the theoretical value (3.690 mg/g). Seventeen anthocyanins were identified by UPLC‒MS/MS. The contents of the main anthocyanins peonidin-3,5- O -diglucoside, malvidin-3,5- O -diglucoside, malvidin-3- O -5- O -(6- O -coumaroyl)-diglucoside, and malvidin-3- O -(6- O - p -coumaroyl)-glucoside in the ChGly extracts were significantly higher than those in the acid‒alcohol extract. Stability assays showed that the stability of anthocyanins in ChGly is higher than that in acidified alcohol at higher temperature, pH and stronger illumination. In vitro antioxidant results showed that the antioxidant capacities of the compounds extracted through the use of UAE-NADES were higher than those extracted using acidified alcohol. Additionally, the thermal behavior of anthocyanin extracts was further characterized through DSC analysis, highlighting the influence of ChGly or acidic ethanol. The results indicate that UAE-NADES exhibits a significant effect on the extraction of anthocyanins from plant byproducts, suggesting that its potential for use in the food sector is considerable.