Optimization of microwave-assisted extraction of total flavonoids from leaves of Moringa oleifera Lam. by response surface methodology and its antibacterial and antioxidant activities

Objective: The purpose of this study is to improve the extraction rate of total flavonoids from the leaves of Moringa oleifera Lam. and evaluate their in vitro antibacterial and antioxidant capacity. Methods: The extraction of total flavonoids from the leaves of M. oleifera Lam. from Baoshan city was optimized by Box-Behnken response surface methodology, and its antibacterial and antioxidant activities were evaluated. Results: The optimal conditions for microwave-assisted extraction of total flavonoids from leaves of M. oleifera Lam. were solid-liquid ratio 1∶29 (g/mL), microwave power 567 W, microwave time 3.6 min and ethanol fraction 50%, and the highest extraction rate of total flavonoids was (7.414±0.027)%. The total flavonoids from leaves of M. oleifera Lam. showed strong DPPH·, ABTS+· and hydroxyl radical scavenging activities, with IC50 value of 0.024 mg/mL, 0.014 mg/mL and 0.051 mg/mL, which were 3.43, 14.00, 1.09 times of ascorbic acid, respectively. Conclusion: The total flavonoids from leaves of M. oleifera Lam. have different degrees of antibacterial effect on B. subtilis and E. coli and have no inhibition on S. aureus.