Abstract: In order to make full use of agricultural waste material—citrus peel,ultrasonic wave-assisted extraction technique of total flavonoids from citrus peel was studied according to a current,rotational and combinational design of quadratic regression.Then,one quadratic regression model for the total flavonoids yield was established.The extraction conditions were optimized by the above model,while the optimized results were verified by experiments.Results showed that the pH value has a very significant effect on the extraction rate of total flavonoids.The ethanol concentration,ratio of solution to material,interaction between time and ethanol concentration,and time and pH value show significant effects on the extraction rate.Other factors have no significant effects on the extraction rate.Research results indicated that the optimized extraction conditions for maximum yield of total flavonoids are:pH value 5.6,ethanol concentration 75%,ratio of solution to material 26 ml/g,and extraction time 80 min.Under the optimized conditions,the experimental value of yield is 3.314%±0.063%(n=3),close to the estimated value 3.348449% attained by regression model.The model for the total flavonoids yield have better prediction effects.

Key words: citrus peel, total flavonoids, ultrasonic wave-assisted extraction, mathematical model, response surface methodology(RSM)