Ultrasonic-microwave collaborative extraction process and antioxidant activity of Flemingia macrophylla leaf flavonoids

【Objective】The ultrasonic-microwave collaborative extraction process of Flemingia macrophylla leaf flavonoids(FMLF) was investigated in this study.Meanwhile, the antioxidant activity of FMLF was studied to provide data basis for the further comprehensive development and utilization of FMLF.【Method】FMLF yield as optimizing targets, fixing ultrasonic power as 50 W, the single factor experiment was adopted to investigate the influence of ethanol concentration, liquid-solid ratio, soaking time, microwave power and extraction time on FMLF yield.Orthogonal design table L₁₆(4⁵) was used to optimize ultrasonic-microwave collaborative extraction process of FMLF, and its ability to remove hydroxyl radical(·OH), superoxide anion radical(O₂^-·), 1, 1-diphenyl-2-picrylhydrazyl radical(DPPH·) and nitrite was measured, in order to evaluate its antioxidant activity in vitro.【Result】The order of various factors affecting the ultrasonicmicrowave synergistic extraction process was:ethanol concentration> microwave power> liquid-solid ratio> soaking time> extraction time, and ethanol volume fraction, microwave power and liquid-solid ratio had significant effects on the extraction effect of FMLF(P< 0.05).The optimized extraction condition of FMLF was as follows:ethanol concentration 60%, liquid-solid ratio 21:1(mL/g), soaking time 8 min, microwave power 400 W, and extraction time 180 s.Under this process condition, the FMLF yield reached 60.25 mg/g, and the efficiency of ultrasonic-microwave collaborative extraction was better than that of the ultrasonic and microwave extraction alone.Within the scope of the experiment, the scavenging effect of FMLF for ·OH, O₂^-, DPPH· and nitrite showed obvious concentration-response relationship with FMLF mass concentration.Clearance rates of FMLF for ·OH, O₂^- and DPPH· and nitrite were 73.05%, 73.82%, 82.54% and 93.04%, respectively, and half scavenging concentration(IC₅₀) were 1.42, 2.88, 0.66 and 1.24 mg/mL, respectively.【Conclusion】The ultrasonic-microwave collaborative extraction method optimized by orthogonal test can be used for the extraction of FMLF.FMLF has certain antioxidant activity and can be used as a natural antioxidant.