Ultrasound-Assisted Simultaneous and Efficient Extraction of Flavonoids and Polysaccharides from Hawthorn ( Crataegus pinnatifida ): Optimization and Bioactivity

Abstract Given the challenges in co-extracting flavonoids and polysaccharides from hawthorn (Crataegus pinnatifida), this study developed a green approach using ultrasound-assisted deep eutectic solvents. Among eleven choline chloride-based DES systems screened, choline chloride-ethylene glycol exhibited the best co-extraction performance, yielding 9.75% for flavonoids and 2.36% for polysaccharides. Under the optimal conditions determined by response surface methodology and single-factor experiments, the yields further increased to 10.48 and 5.96%, far exceeding ethanol and water yields. After purification using AB-8 macroporous resin under optimized parameters and after five reuse cycles, the retention rates of flavonoids and polysaccharides relative to the first extraction were 94.37 and 83.56%, respectively, confirming the desirable reusability of DES. Notably, DES-extracted flavonoids demonstrated superior antioxidant activity compared to conventional ethanol extracts. The co-extracted polysaccharides had a weight-average molecular weight (Mw) of 209,567.43 Da, and monosaccharide composition analysis revealed that galacturonic acid accounted for 90.26% of the total, indicating high pectin purity. FTIR and 1H NMR revealed that the DES extract had higher polysaccharide content and a more intact backbone, and both extracts had α-glycosidic linkages and heteropolysaccharide signals. Overall, this work provides a recyclable and eco-friendly strategy for the simultaneous extraction of multiple bioactive components from natural products using DES.