Objective: To develop a SPE-HPLC method for the determination of saikosaponin D in rat plasma after being administered Radix Bupleuri water extract intragastrically. Method: The blood was taken from rat orbital venous at different time points

and the plasma was purified by using the Waters Oasis solid-phase extraction column. The eluate was dried with nitrogen

and then dissolved with mobile phase. The saikosaponin D was analyzed by chromatographic system consisting of YMC-Pack ODS C18column and acetonitrile-water as mobile phase. Result : Saikosaponin D was linear in range of 1.28-81.60 μg ·mL-1 (r = 0.997 8). And the quantitative limit was 1.28 μg ·mL-1. Relative recovery was 94.6%-102.8%; And the within-day precision and between-day precision were less than 8% (RSD). Conclusion: This method is sensitive

accurate

and can be used for determination of saikosaponin D in rat plasma.