Gut microbiota-mediated deglycosylation of ginsenoside Rb1 in rats: in vitro and in vivo insights from quantitative ultra-performance liquid chromatography-mass spectrometry analysis

Abstract

Ginsenoside Rb₁, an ingredient of the herbal medicine Panax ginseng, possesses a variety of biological activities. Gut microbiota mediated deglycosylation of ginsenoside Rb₁ has long been proposed to play an important role in mediating its pharmacological effects. However, the major active ginsenoside components after the gut microbial transformation have not been clearly identified. To obtain pharmacokinetic clues, we first established a rapid and sensitive ultra performance liquid chromatography (UPLC) tandem mass spectrometry method for targeted analysis of ginsenoside Rb₁-related components (ginsenoside Rd, F₂, Rg₃, Rh₂ and compound K) in biological samples. We then performed a comprehensive quantitation of ginsenoside Rb₁ and its metabolites in rat plasma after oral administration of ginsenoside Rb₁. In vitro microbial hydrolysis of ginsenoside Rb₁ was further investigated to help elucidate the in vivo findings. The results indicated that ginsenoside Rb₁ and ginsenoside Rd could be detected within 72 hours after oral administration of ginsenoside Rb₁. Other metabolites, like compound K, only appeared at a very low concentration in the circulation. The in vitro hydrolysis study revealed that the formation of ginsenoside Rg₃ and Rh₂ was relatively low compared with the ginsenoside Rd, F₂ and compound K. Ginsenoside Rb₁ was rapidly hydrolyzed to ginsenoside Rd and the formation of F₂ from Rd paralleled compound K from F₂. Together, our work suggested that ginsenoside Rd could be the major circulating active metabolite of ginsenoside Rb₁ mediated by gut microbial deglycosylation in rats.