Characterization of oxygenated metabolites of ginsenoside Rg₁ in plasma and urine of rat

This study describes the characterization of oxygenated metabolites of ginsenoside Rg₁ in rat urine and plasma. These in vivo metabolites were profiled by using UHPLC-QTOF MS-based method. On the basis of high-resolution MS/MS data, and comparison with chemically synthesized authentic compounds, nine oxygenated metabolites of Rg₁ were characterized as vinaginsenosides 21 and 22 (M1 and M2), vinaginsenoside R15 (M3), 6-O-(β-D-glucopyranosyl)-20-O-(β-D-glucopyranosyl) 3β, 6α, 12β, 20(S)-tetrahydroxy-24ξ-hydroxydammar-25-ene (M4 and M5), floralginsenoside A (M7 and M8), floralginsenoside B (M9) and epoxyginsenoside Rg₁ (M13), respectively. Among these metabolites, M4, M5 and M13 are new ginsenosides and others were detected as in vivo metabolites of Rg₁ for the first time. In addition, a series of oxygenated metabolites of Rh₁ and deglycosylated metabolite of Rg₁, were observed and characterized by comparing with compounds synthesized by us, which revealed an association between C-20 configuration and the extent of oxidation metabolism. Appearance of all these metabolites in blood stream and urine after i.v. dosing and oral administration of Rg₁ was further examined, which clearly showed that mono-oxygenated metabolites of Rg₁ were major circulating metabolites at the early stage after dosing. Characterization of exact chemical structures of these circulating metabolites contribute greatly to our understanding of chemical exposure after consumption of ginseng products, and provide valuable information for explaining multiple bioactivities of ginseng products.