Optimization of Extraction Process of Flavonoids from Aronia melanocarpas' Leaves and Analysis of Their Antioxidant and Bile Salt Binding Capacity

In this study, the antioxidant and bile salt binding activities of flavonoids from Aronia melanocarpas' leaves (AMF) by ultrasound-assisted extraction. Based on single factors (liquid-solid ratio, ethanol concentration, ultrasonic power and ultrasonic time) and response surface method, the extraction process of AMF was optimized with flavonoid yield as the index. The antioxidant activity of AMF was evaluated by DPPH·, ABTS⁺· scavenging rate and reduction power. The bile salt binding ability of AMF was investigated by using sodium cholate, sodium taurocholate and sodium glycocholate as binding objects. The results showed that the optimal extraction conditions were as follows: The liquid-solid ratio of 61:1 mL/g, the ethanol concentration of 60%, the ultrasonic power of 100 W, and the ultrasonic time of 59 min. Under the optimized conditions, the yield of flavonoids was 24.22%±0.29%, which approximated the predicted value (24.27%). The IC₅₀ of DPPH and ABTS⁺ radicals scavenging capacities of AMF were 0.32 and 0.16 mg/mL, respectively. The AMF demonstrated the strongest reducing power with an absorbance value of 1.09 at the sample concentration of 0.5 mg/mL. The IC₅₀ of AMF for the binding rate of sodium cholate, sodium taurocholate and sodium glycocholate were 0.76, 3.01 and 6.49 mg/mL, respectively. In summary, AMF exhibited strong antioxidant and bile salt binding capacity. This study could provide a basis for AMF to further develop natural antioxidants and hypolipidemic drugs.