Optimization of Total Polyphenols Extraction from Vigna angularis and their Antioxidant Activities

Vigna angularis, also called adzuki bean, a member of the family Fabaceae, has long been cultivated in Asian countries. This legume has received considerable attention owing to the presence of polyphenols. The optimal extraction conditions for total polyphenols from V. angularis and their antioxidant activities were investigated in this study. Ultrasound-assisted extraction was used to optimize the extraction of total polyphenols from V. angularis. Factors that influenced the extraction efficiency, such as ethanol concentration, liquid-solid ratio, and ultrasonic time were investigated by Box-Behnken design. Folin-Ciocalteu colorimetry was adopted to determine the total polyphenol content by using gallic acid as a reference. Antioxidant activities of the total polyphenols were evaluated by 1,1-diphenyl-2-picrylhydrazyl, hydroxyl and superoxide radical-scavenging activity assays. The optimized extraction conditions were as follows: ethanol concentration of 44.3%; liquidsolid ratio of 21.6:1 and ultrasonic extraction time of 30 min. Under these optimal conditions, the model’s predicted extraction efficiency was 4.19 mg/g. The mathematical model had a high correlation (P<0.05) and could be employed to extract total polyphenols from V. angularis. In vitro antioxidant activity results showed that total polyphenols had strong antioxidant capacity and could be used as potential antioxidant agents. This study provided a reference for the exploration of new natural antioxidants.