Chemical and metabolic analysis of Achyranthes bidentate saponins with intestinal microflora-mediated biotransformation by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry coupled with metabolism platform.

Achyranthes bidentate (AB) is a typical traditional Chinese medicine (TCM) that has been widely used in clinical practices for more than a thousand years. Modern pharmacological studies have shown that triterpene saponins are the main pharmacological active ingredients in AB. Meanwhile, the poor oral bioavailability of triterpene saponins in AB indicates that these ingredients are probably metabolized by intestinal microflora before absorption. In this work, an integrated analysis based on ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) combined with a metabolism platform was developed to identify the chemical constituents and intestinal metabolic profiles of triterpene saponins in AB. As a result, a total of 40 triterpene saponins (including thirty-eight oleanane-type, one hederagenin-type and one machaerinate-type triterpene saponin) were identified from the AB extract. Moreover, 39 biotransformation products mediated by intestinal microflora were characterized, which mainly underwent four metabolic reactions including deglycosylation, glycosylation, oxidation and dehydrogenation. To our knowledge, the in vitro metabolites of AB through intestinal microflora metabolism, especially triterpene saponins, have not been studied previously. The obtained results could be helpful for the further evaluation of the pharmacokinetics and the pharmacological activity of triterpene saponins of AB in vivo.