Simultaneous enantiomer determination of 20 ( R)- and 20 ( S)-ginsenoside-Rg 2 in rat plasma after intravenous administration using HPLC method

Abstract

20 ( R, S)-Ginsenoside-Rg 2, an anti-shock agent, is prescribed as a racemate. To analyze simultaneously the enantiomers of 20 ( R)-ginsenoside-Rg 2 and 20 ( S)-ginsenoside-Rg 2 in plasma, a simple and reproducible high-performance liquid chromatographic (HPLC) method has been developed. The enantiomeric separation and determination were successfully achieved using a Diamonsil™ ODS C 18 reversed-phase column (5 μm, 250 mm × 4.6 mm) with an RP18 (5 μm) guard column and a mobile phase of MeOH- aq. 4% H 3PO 4 (65:35, v/v, pH 5.1) with UV detection at 203 nm. Both enantiomers, 20 ( R)-ginsenoside-Rg 2 and 20 ( S)-ginsenoside-Rg 2, were well separated at 14.5 min and 13.6 min, respectively. The linear ranges of the standard curves were 2.0–250 μg/ml. The intra- and inter-day precision (R.S.D.) were ≤1.59% and ≤0.54% and the mean extraction recoveries were 95.8% and 96.5% for 20 ( R)-ginsenoside-Rg 2 and 20 ( S)-ginsenoside-Rg 2 in rat plasma, respectively. The limits of detection and quantification were 2.0 μg/ml and 7.8 μg/ml (S/N = 3:1) for 20 ( R)-ginsenoside-Rg 2, and 2.0 μg/ml and 3.9 μg/ml (S/N = 3:1) for 20 ( S)-ginsenoside-Rg 2, respectively. This validated method was applicable to pharmacokinetic studies in rat plasma after intravenous administration of 20 ( R, S)-ginsenoside-Rg 2. A pharmacokinetic study in rat plasma indicated that the enantiomers were rapidly absorbed and eliminated. These assay results are necessary for the evaluation of the metabolism of ginsenoside-Rg 2 in vivo.