Abstract: To explore the optimal ultrasonic extraction process for forsythoside and forsythoside A from Forsythia suspensa branches and leaves,the single-factor test combined with response surface test design, the mathematical model with the extraction rates of forsythoside and forsythoside A as the evaluation indexes to screen the optimal process parameters, such as the solid-liquid ratio, extraction time and ethanol concentration. The results showed that the optimal extraction condition for forsythoside was solid-liquid ratio of 20∶1 mL∶g, ethanol concentration of 30%, and extraction time of 30 min; while the optimal extraction condition for forsythoside A was solid-liquid ratio of 45∶1 mL∶g, ethanol concentration of 50%, and extraction time of 30 min. Verification experiment indicated that under the above extraction conditions, the relative standard deviation between the actual extraction rate of forsythoside and the predicted value was 0.3%(< 3%), and that of forsythoside A was 2.5% (< 3%), which confirmed that the model was reliable and the process was stable. The established optimization method provided a technical reference for the efficient extraction of forsythoside and forsythoside A from the branches and leaves of Forsythia suspensa.

Key words: Forsythia suspensa branches and leaves, forsythoside, forsythoside A, ultrasonic extraction method, response surface methodology