Abstract: Objective: To establish an high performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD) method for the simultaneous determination of oleanolic acid and ursolic acid in the leaves of Forsythia suspensa. Methods: The chromatographic separation was carried out on a Waters Symmetry C18 column (4.6 mm× 250 mm, 5 μm) with a mobile phase composed of methanol and 0.4% acetic acid (93:7, V/V) at a flow rate of 0.4 mL/min. An evaporative light scattering detector was used to detect oleanolic acid and ursolic acid with a drift tube temperature of 80 ℃ and a gas pressure of 25 psi. Results: Both the developed calibration curves of oleanolic acid and ursolic acid revealed a good linear relationship over the ranges of 0.107－2.136 μg (r = 0.9991) and 0.179－3.584μg (r = 0.9993), respectively. The recovery rates of oleanolic acid and ursolic acid were 98.67% and 98.56%, respectively. Conclusion: A simple, accurate and credible HPLC-ELSD method has been developed, which is suitable for the quality contro1 of the leaves of Forsythia suspensa.

Key words: leaves of Forsythia suspensa, high performance liquid chromatography -evaporative light scattering detector(HPLC-ELSD), oleanolic acid, ursolic acid