Abstract
20(S)-Ginsenoside Rh2 (Rh2)-containing products are widely used in Asia, Europe, and North America. However, extremely limited metabolism information greatly impedes the complete understanding of its clinical safety and effectiveness. The present study aims to systematically investigate the oxidative metabolism of Rh2 using a complementary set of in vitro models. Twenty-five oxidative metabolites were found using liquid chromatography-electrospray ionization ion-trap mass spectrometry. Six metabolites and a metabolic intermediate were synthesized. The metabolites were structurally identified as 26-hydroxy Rh2 (M1-1), (20S,24S)-epoxydammarane-12,25-diol-3-β-d-glucopyranoside (M1-3), (20S,24R)-epoxydammarane-12,25-diol-3-β-d-glucopyranoside (M1-5), 26,27-dihydroxy Rh2 (M3-6), (20S,24S)-epoxydammarane-12,25,26-triol-3-β-d-glucopyranoside (M3-10), (20S,24R)-epoxydammarane-12,25,26-triol-3-β-d-glucopyranoside (M3-11), and 26-aldehyde Rh2 on the basis of detailed mass spectrometry and nuclear magnetic resonance data analysis. Double-bond epoxidation followed by rearrangement and vinyl-methyl group hydroxylation represent the initial metabolic pathways generating monooxygenated metabolites M1-1 to M1-5. Further sequential metabolites (M2–M5) from the dehydrogenation and/or oxygenation of M1 were also detected. CYP3A4 was the predominant enzyme involved in the oxidative metabolism of Rh2, whereas alcohol dehydrogenase and aldehyde dehydrogenase mainly catalyzed the metabolic conversion of alcohol to the corresponding carboxylic acid. No significant differences were observed in the phase I metabolite profiles of Rh2 among the five species tested. Reactive epoxide metabolite formation in both humans and animals was evident. However, GSH conjugate M6 was detected only in cynomolgus monkey liver microsomal incubations. In conclusion, Rh2 is a good substrate for CYP3A4 and could undergo extensive oxidative metabolism under the catalysis of CYP3A4.
Footnotes
This work was supported by the National Science and Technology Major Project “Key New Drug Creation and Manufacturing Program,” China [Grant 2009ZX09301-001].
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
↵ The online version of this article (available at http://dmd.aspetjournals.org) contains supplemental material.
ABBREVIATIONS:
- Rh2
- 20(S)-ginsenoside Rh2
- PPD
- 20(S)-protopanaxadiol
- P-gp
- P-glycoprotein
- P450
- cytochrome P450
- HLM
- human liver microsomes
- CyLM
- cynomolgus monkey liver microsomes
- DLM
- dog liver microsomes
- RLM
- rat liver microsomes
- MLM
- mouse liver microsomes
- GEE
- GSH ethyl ester
- NAC
- N-acetyl-l-cysteine
- HPLC
- high-performance liquid chromatography
- m-CPBA
- 3-chloroperoxybenzoic acid
- LC
- liquid chromatography
- MSn
- ion-trap mass spectrometry
- MSD
- mass selective detector
- MS
- mass spectrometry
- NMR
- nuclear magnetic resonance
- GST
- glutathione transferase.
- Received May 30, 2012.
- Accepted July 24, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
DMD articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|