Abstract: A sensitive and selective high performance liquid chromatography coupled with electrospray ionization mass spectrometry (LC-MS) was developed for the quantitative determination of ilexgenin A (IA), a major component in Radix Ilicis Pubescentis, in rat plasma. Chromatographic separation was performed on a C18 column, with methanol -5 mM ammonium acetate (80:20, v/v) as the mobile phase. Mass spectrometer was set in negative mode with target ions at m/z 501.1→501.1 for IA and m/z 779.4→779.4 for digoxin (internal standard, IS). Rat plasma was extracted with ethyl acetate after addition of phosphoric solution and the organic layer was evaporated and reconstituted with mobile phase for LC-MS analysis. The proposed method was validated with a linear range of 1.05-525.5 ng/mL for IA with limit of quantitation (LOQ) at 1.05 ng/mL. Intra- and inter-day precision expressed as relative standard deviation (RSD) were less than 10% at LOQ level and overall recovery was over 80%. This validated method was used successfully for the pharmacokinetic study of IA in rats after oral dosing of IA (100 mg/kg) and some main pharmacokinetic parameters of IA in rats were obtained.

Key words: High performance liquid chromatography, Electrospray ionization mass spectrometry, Ilexgenin A, Radix Ilicis Pubescentis, Pharmacokinetic study