Microwave Extraction Technique of Polyphenols and in Vitro Antioxidation Activity from the Leaves of Azadirachta Indica A.Juss.

OBJECTIVE To optimize the microwave extraction technique of polyphenol from Azadirachta indica A. Juss. leaves by response surface methodology and to evaluate the in vitro antioxidant activity of polyphenol in leaves of Azadirachta indica A.Juss.. METHODS The experiment was designed by single factor experiment and response surface method. The influence and the interaction of three response variables such as extract temperature, extraction time, ethanol concentration were investigated. The extraction technology was optimized. The antioxidant activities of polyphenol extracted from Azadirachta indica A. Juss. leaves were evaluated through clearing the DPPH·, ·OH free radical and reducing power. RESULTS The optimum microwave extraction conditions of polyphenol in the Azadirachta indica A. Juss. leaves were extraction temperature 62 ℃, extraction time 40 min, ethanol concentration 48%. The influence order of response variables was extraction temperature, ethanol concentration, extraction time. The average extract ratio of Azadirachta indica A. Juss. leaves polyphenol was 2.96% and the relative error was 1.33%. The IC₅₀ values of Azadirachta indica A. Juss. leaves phenolics scavenging activity on DPPH was about 2.6 mg·L^-1. The IC₅₀ values of Azadirachta indica A. Juss. leaves phenolics scavenging activity on ·OH was about 15 mg·L^-1. The reduction ability of Azadirachta indica A. Juss. leaves polyphenols was strong at lower concentration. CONCLUSION The antioxidant activities of polyphenol extracted from Azadirachta indica A. Juss. leaves were stronger than that of Vc at low concentration.