In vitro biotransformation of red ginseng extract by human intestinal microflora: Metabolites identification and metabolic profile elucidation using LC–Q-TOF/MS

• A strategy for identification of ginseng saponins and their metabolites was proposed. • Totally 30 metabolites were characterized in the red ginseng extract biotransformed by human intestinal microflora. • Ginsenoside lactate esters were firstly detected and identified. • Metabolic pathways of red ginseng saponins were elucidated. Ginseng is an important and widely used herbal medicine in Asia and has gained popularity in the western countries. Ginseng products are usually administered orally, after which their complicated components are brought into contact with intestinal microflora in the alimentary tract and metabolized. The metabolic investigation of ginseng in intestinal tract is necessary for elucidating its pharmacological activities. However, most of the reports about the metabolism of ginseng with intestinal microflora are focused on single ginseng saponin with the whole action of ginseng extract ignored. In the present paper, in vitro biotransformation of red ginseng extract by human intestinal microflora was conducted, and a rapid liquid chromatography with time-of-flight mass spectrometry (LC–Q-TOF/MS) method was used for rapid identification of the metabolites and metabolic profile of ginseng saponins. A total of 37 ginseng saponins in red ginseng extract were characterized, 17 of which were assessed to be metabolized by human intestinal microflora. Also, 30 metabolites, mostly deglycosylated, were detected and identified in the biotransformed red ginseng extract, including 4 original ingredients of red ginseng, 6 ginsenoside lactate esters, and 2 glycosylated metabolites. The metabolic profile of ginseng saponins biotransformed by human intestinal microflora was elucidated based on the metabolite information. The results indicated that deglycosylation was the major metabolic pathway of saponins in red ginseng. The esterification and glycosylation reaction also occurred during the biotransformation. Our study indicated that there was some differences in the biotransformation of single ginseng saponin and red ginseng extract. It must be noted that the ginsenoside lactate esters were firstly found in the metabolites of ginsenosides.