Abstract: In order to investigate ultrasonic extraction technology of ursolic acid from Paulownia elongate leaves,central composite design coupled with response surface analysis was adopted to study the effects of ethanol concentration (X₁), ratio of liquid to solid (X₂) and ultrasonic time (X₃) on the extraction yield of ursolic acid.The results showed that the effects of ultrasonic factors on the extraction yield of ursolic acid from P.elongate leaves were in the following order:ethanol concentration (X₁) > ultrasonic time (X₃) > ratio of liquid to solid (X₂),and the optimal extraction conditions were as follows:89% ethanol solution as extraction solution,30 mL/g as the ratio of liquid to solid,37 min as ultrasonic time.Under the optimal conditions,the extraction yield of ursolic acid reached 14.80 mg/g,which was close to the predicted response value.Hence,the quadratic regression model can be used to predict the ultrasonic extraction conditions of ursolic acid from P.elongate leaves.

Key words: central composite design, Paulownia elongate leaves, ultrasonic extraction, ursolic acid