Extraction of flavonoids from Cyclocarya paliurus (Juglandaceae) leaves using ethanol/salt aqueous two-phase system coupled with ultrasonic

An aqueous two phase system (ATPS) coupled with ultrasonic was employed to extract flavonoids from Cyclocarya paliurus (Batalin) Iljinskaja leaves first time. The optimal conditions were determined by Response Surface Methodology(RSM) of ethanol concentration 33%; salt concentration 15%; extraction time 52 min; liquid-solid ratio 33:1, while the flavonoids extraction yield obtained the maximum of 3.00 +/- 0.1%. The antioxidant activity of flavonoids was evaluated by vitro antioxidant assays under the optimal conditions, which indicated that the extract has strong DPPH, ABTS + and superoxide anion radical-scavenging activity (IC50 value of 0.0013 mg/ml, 0.0296 mg/ml and 0.126 mg/ml) which were close to and even better than Vc (extremely close to 0, 0.0291 mg/ml and 0.433 mg/ml). The study showed that the ATPS-ultrasonic was a commendable approach for the extraction of flavonoids from C. paliurus and the flavonoids may serve as new natural antioxidant for functional food ingredients and additives. Practical applications In this study, ethanol and inorganic salt are selected as the extraction and separation solvent, which is simpler than the traditional method, environmental friendly, while reducing the process cost, and has great application value. Furthermore, through the analysis of the extraction components of the edible plant Cyclocarya paliurus, it was found that the flavonoids contained in C paliurus had antioxidant activity close to vitamin C. Combined with the above research, C. paliurus has the potential to develop into functional food and additives with antioxidant function.