Abstract:   In order to investigate enzymolysis-ultrasonic-assisted extraction of total polyphenols from degreasing Cinnamomum caraphora (L.) Presl leaves,Box-Behnken design coupled with response surface analysis based on the single factor experiments was adopted to study the effects of influencing factors including cellulase dosage(X₁),ethanol concentration (X₂) and liquid-solid ratio (X₃) on the extraction rate of total polyphenols.Antioxidant activity of extract of total polyphenols was estimated by testing DPPH radical and hydroxyl radical scavenging ability.The results showed that the effects of above factors on the extraction rate of total polyphenols from degreasing C.caraphora leaves were in the following order:liquid-solid ratio (X₃) > ethanol concentration (X₂) > cellulase dosage (X₁),and the optimal extraction conditions were as follows:1% as cellulase dosage,55% ethanol solution as extraction solution,30 mL/g as ratio of liquid to solid,50 ℃ as enzymolysis temperature,1.5 h as enzymolysis time,30 min as ultrasonic time,45 kHz as ultrasonic frequency,360 W as ultrasonic power,70  ℃ as ultrasonic temperature.Under the optimal conditions,the mean value of extraction rate of total polyphenols reached 22.08 mg/g,which was close to the predicted response value.Therefore,the quadratic regression model can be used to predict the enzymolysis-ultrasonic-assisted extraction conditions of total polyphenols from degreasing C.caraphora leaves.Extract of total polyphenols exhibited a dose-dependent scavenging activity against DPPH radical and hydroxyl radical.Its half maximal inhibitory concentration (IC₅₀) were 0.36 and 0.15 mg/mL,respectively,which suggested extract of total polyphenols had high antioxidant activity.

Key words: Box-Behnken design, degreasing Cinnamomum caraphora , leaves, enzymolysis-ultrasonic-assisted extraction, total polyphenols, antioxidant activity