Ultrasound-assisted deep eutectic solvent extraction of bioactive compounds from persimmon calyx

Abstract: This study aimed to investigate the ultrasound-assisted extraction of bioactive compounds from persimmon (Diospyros kaki) calyx by deep eutectic solvents (DES) with different molar ratios. For this reason, the prepared DES extracts’ total phenolic–flavonoid compounds and antioxidant activities (1,1-diphenyl-2-picrilhydrazyl radical scavenging activity [DPPH•], Cupric Reducing Antioxidant Capacity (CUPRAC), and ferric reducing antioxidant power [FRAP]) were investigated as a result of the experimental design and optimization study conducted for this purpose. A sonication time of 20 min was determined as the optimal condition. Under these conditions, a molar ratio of 1.9:1 (lactic acid:choline chloride) and a water ratio of 70% provided the highest phenolic/flavonoid compounds and antioxidative activity. Correlations among water ratio, molar ratio, and sonication time were determined using principal component analysis (PCA). In conditions where total flavonoid compound, FRAP, and DPPH• are high due to PCA, it can be concluded that the sonication time is at high level; on the contrary, the water and molar ratios are at low level. In conclusion, ultrasound-assisted extraction using DES proved effective in persimmon calyx. Therefore, it can be recommended to use these environmentally friendly green solvents as an alternative to organic solvents in preparing extracts in various fields. Practical Application: This study shows the effectiveness of the ultrasound-assisted green extraction method using persimmon calyx specified as waste. These findings are compelling in the food industry in terms of consumers being now aware of green technology and the discovery that calyx is a good source of bioactive compounds.