Green and efficient extraction process of flavonoids from sea buckthorn fruits by natural deep eutectic solvents aided with ultrasound

[Display omitted] •Green NADES (betaine-lactic acid) was selected for the first time to extract flavonoids from sea buckthorn fruit.•Higher extraction rate than traditional solvent.•The best extraction process was optimized by Response surface method. In recent years, with the advantages of environment friendly, natural deep eutectic solvents (NADES) have been gradually applied for the extracting bioactive compounds from natural products. In this study, NADES-12 (betaine-lactic acid, n/n, 1:2) was selected for the first time to extract flavonoids from sea buckthorn fruit after screening of 23 NADES. The optimal technical conditions of NADES combined with ultrasonic assisted extraction (UAE) were determined by single factor test and response surface optimization test. The results showed that the optimal process for the extraction of antioxidant components by NADES-12 was 37 min extraction time, 40 °C extraction temperature, 17 % (v/v) water content, 40 mL mg−1 liquid–solid ratio, 160 W ultrasonic power, and a maximum extraction rate of 5.248 mg g−1, and the extraction yield is 2.4 and 3.1 times that of 60 % ethanol and water. The sea buckthorn extract by NADES has antioxidant activity. The study proposes a green and efficient method for the extraction of bioactive components from sea buckthorn fruit and provides a valuable basis for the exploitation of other natural plants.