Determination of 20(S)-Ginsenoside Rh1 and its Aglycone 20(S)-Protopanaxatriol in Rat Plasma by Sensitive LC-APCI-MS Method and its Application to Pharmacokinetic Study

A liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) method has been developed for the measurement of the concentrations of 20(S)-ginsenoside Rh1 and its aglycone 20(S)-protopanaxatriol in rat plasma with panaxatriol as the internal standard. The method involved single liquid–liquid extraction of both 20(S)-ginsenoside Rh1 and 20(S)-protopanaxatriol from plasma samples with n-butanol. The limit of quantification (LOQ) was 5 ng mL⁻¹ for both compounds. The method was validated within the linear range 5–2000 ng mL⁻¹ for both compounds. The correlation coefficient for the calibration regression line was 0.999 or better. Intra-day and inter-day accuracy were better than 15%. The method has successfully been used for pharmacokinetic studies in rats. After intravenous administrations, the mean retention times of 20(S)-ginsenoside Rh1 and 20(S)-protopanaxatriol were 17.1 ± 2.0 min and 3.46 ± 0.33 h, respectively.