Ultrasonic assisted extraction of polyphenol from loquat leaves and its antioxidant activity

ObjectiveUltrasonic assisted extraction of polyphenols from loquat leaves was optimized by response surface method,and antioxidant activity of polyphenols in loquat leaves was evaluated to provided technique support for the development and utilization of loquat leaf polyphenol.MethodAccording to the principle of Box-Behnken,the influ-encing parameters including extraction temperature,extraction time,solid-liquid ratio and ethanol concentration were op-timized using response surface method on the basis of single factor experiment. The optimum processing conditions of polyphenol extraction from loquat leaves by ultrasonic assisted method were determined,and the extraction rate was com-pared with that in traditional solvent-extraction method.The antioxidant properties of loquat leaf polyphenols were investi-gated with the scavenging rate of hydroxyl radical and DPPH as indicators.ResultOptimum processing conditions for ul-trasonic assisted loquat leaf polyphenol extraction obtained by the response surface design analysis were as follows:extrac-tion temperature was 67℃,extraction time 40 min,solid-liquid ratio 1:25 and ethanol concentration 60%.The total poly-phenol yield from loquat leaf was 48.24 mg/g in the optimal conditions,which was consistent with the predicted value (48.79 mg/g).Extraction temperature,interaction between extraction temperature and solid-liquid ratio,interaction be-tween extraction time and solid-liquid ratio had significant effects on loquat leaf polyphenol extraction(P<0.05). Com-pared with the traditional solvent extraction method,ultrasonic assisted extraction method was a extraction technology with high efficiency and shorter time.The scavenging capacity of loquat leaf polyphenol to hydroxyl radicals and DPPH free radicals strengthened with the increase of concentration of polyphenol in loquat leaf.When the concentration of loquat leaf polyphenol was 20 μg/mL,the scavenging rates of the two free radicals were respectively 40% and 56%.Conclu-sionThe processing conditions of ultrasonic assisted extraction of loquat leaf polyphenol are reasonable and feasible. Compared with traditional extraction method,ultrasonic assisted extraction can significantly improve the yield of polyphe-nol.Loquat leaf polyphenol has good antioxidant properties.