Sarsasapogenin(SG),a natural compound from traditional Chinese medicinal herb Anemarrhena asphodeloides Bge.,has recently received a great deal of attention due to its wide variety of bioactivities.In this study,SG was measured after protein precipitation with methanol using diosgenin as internal standard(IS)and liquid chromatography-tandem mass spectrometry(LC-MS/MS)for detection.Chromatographic separation was achieved on a Poroshell 120 EC-C18(150 mm × 3.0 mm i.d.,2.7 μm)column using a mobile phase consisting of methanol and water(containing 5 mM ammonium acetate)with isocratic elution.The MS/MS analysis was performed in positive ionization mode monitoring the m/z transitions 417.4/273.2 for SG and 415.2/271.4 for IS.The linear range was 0.5-500 ng/mL(r = 0.9994)for SG with the lower limit of quantitation of 0.5 ng/mL.The intra-and inter-day precision RSD was below 6.41%and accuracy was from 87.60%to 99.20%.The RSD of matrix effect and recovery yield were within ±15%of nominal concentrations and SG was stable during stability studies.The developed LC-MS/MS was shown to be valid and successfully applied to measure plasma-concentration-time curves of SG in a pilot study in rats.The elimination half-lives(t1/2)were(15.1 ± 2.3),(16.1 ± 3.0)and(15.4 ± 3.9)h after a single intragastric administration of 25,50 and 100 mg/kg SG,respectively.The area under the plasma concentration versus time curve(AUC0-72 h)and peak plasma concentration(Cmax)were linearly related to dose.