Liquid Chromatography-Quadrupole Time-of-Fight Mass Spectrometry-Based Analysis of American Ginseng Saponins Transformed by Human Intestinal Microflora
American ginseng is a widely used natural product. Ginseng products are usually taken orally, and human intestinal microflora may metabolize ginsenoside. Existing publications report the metabolite fates of ginsenoside . However, investigations on the comprehensive metabolic profile of American ginseng extract are scarce because of the chemical complexity and limitation of analytical methods. In this work, we studied the biotransformation and metabolic profile of American ginseng extract by human intestinal microflora. Human fecal microflora was prepared from a healthy Chinese man and then anaerobically incubated with American ginseng sample at 37 °C for 24h . A highly sensitive and selective liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) method was used to characterize ginsenosides and related metabolites in the reaction samples. A total of 25 metabolites were detected, 13 of which were undoubtedly assigned by comparison with reference compounds, and 12 others were tentatively identified. The three most abundant metabolites are 20S-ginsenoside Rg3, ginsenoside F2 and compound K. The main metabolic pathways of ginseng saponins are deglycosylation reactions by intestinal microflora through stepwise cleavage of the sugar moieties. Subsequent dehydration reactions also occur. Protopanaxdiol- and oleanane-type triterpenoids are easy to be metabolized. The intestinal microbiota may play an important role in mediating the metabolism bioactivity of American ginseng. Acknowledgements: This work was supported in part by the National Science Foundation of China (No. 81173497 and 81222052), NIH/NCCAM Grants AT004418 and AT005362. Our thanks go to Yu-Ting Yan from China Pharmaceutical University for providing Q-TOF-MS analysis. References:  Liu H, Yang J, et al. (2009) Drug Metabolism and Disposition, 37: 2290 - 2298.  Jung I-H, Lee JH, et al. (2012) Biological & Pharmaceutical Bulletin, 35(4): 573 - 581.