Objective: To optimize ultrasonic-assisted extraction technology of betulinic acid from Forsythiae Fructus using response surface methodology. Method: On the basis of single factor tests

Box-Behnken experimental design and response surface methodology was adopted to optimize extraction conditions with the concentration of ethanol

extraction temperature and solid-liquid ratio as factors.HPLC was used to determine the content of betulinic acid from Forsythiae Fructus

chromatographic conditions were as follows:Thermo Hypersil GOLD AQ-C18 column (4.6 mm×250 mm

5 μm)

acetonitrile-water (9: 1) as mobile phase

flow rate of 1.2 mL·min-1

injection volume 20 μL

detection wavelength at 210 nm. Result: Optimal ultrasound-assisted extraction technology of betulinic acid from Forsythiae Fructus was as following:the volume fraction of ethanol 80%

extraction temperature 37℃

liquid-solid ratio 32 mL·g-1.The actual value of betulinic acid yield was (4.28±0.05) mg·g-1

which was consistent with the predicted value of 4.30 mg·g-1. Conclusion: This optimized extraction process was reasonable and reliable with high yield of effective components.