Optimization of flavonoids extracted from hawthorn （Crataegus pinnatifida） by ultrasonic-assisted deep eutectic solvent

Hawthorn flavonoids have received extensive attention in agriculture, pharmaceutical and food industries due to their rich biological activities. In this study, deep eutectic solvent (DES) was used to extract flavonoids from hawthorn. Under optimal conditions, with a molar ratio of ethylene glycol to choline chloride at 2:1, DES volume fraction 70%, the solid-liquid ratio of 30:1 (mL/g), and an Ultrasound time of 30 min, the yield of hawthorn flavonoids was 57.82 ± 0.04 mg/g. The measured results were consistent with the prediction. After extracting hawthorn flavonoids, DES was recovered by polyamide resin. The recovery rate reached 91.53% ± 0.12%. Finally, HPLC method was used to compare the content and composition of hawthorn flavonoids extracted by DES compared with ethanol. The experimental results showed that DES had a higher yield and a slightly different composition from ethanol-assisted ultrasonic extraction. In conclusion, the deep eutectic solvent has good application prospects in extracting hawthorn flavonoids.