Identification of the metabolites of erianin in rat and human by liquid chromatography/electrospray ionization tandem mass spectrometry.

RATIONALE: Erianin, a bioactive component isolated from Dctidrobium chrysotoxum Lindl, was demonstrated to have many biological properties relevant to cancer prevention and therapy. However, the metabolic profiles of erianin remain unknown. This study was carried out to investigate the metabolic profiles of erianin in rats and humans. METHODS: Erianin was orally administered to rats at a single dose of 50 mg/kg. Urine and bile samples were collected. For in vitro metabolism, erianin was co-incubated with rat or human hepatocytes at 37°C for 2 h. The samples from incubations and rat were analyzed by liquid chromatography combined with electrospray ionization high-resolution mass spectrometry. The data were processed by MetWorks software. The structures of the metabolites were proposed by comparing the mass spectra with that of the parent compound. RESULTS: A total of twenty-four metabolites were detected in vitro and in vivo, including seven phase I and eighteen phase II metabolites. The phase I metabolic pathways of erianin were hydroxylation, demethylation and dehydrogenation. Erianin undergoes metabolic activation to form reactive metabolites quinoid intermediates, which were further trapped by glutathione (GSH) or N-acetylcysteine. The phase II metabolic pathways were glucuronidation, glutathione and N-acetylcysteine conjugation. CONCLUSIONS: The present study provides an overview pertaining to the in vitro and in vivo metabolic profiles of erianin, which is indispensable for us to understand the efficacy and safety of erianin, as well as the herbal medicine D. chrysotoxum.

Identification of the metabolites of gigantol in rat urine by ultra-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry.

Gigantol is a typical bibenzyl compound isolated from Dendrobii Caulis that has been widely used as a medicinal herb in China for the treatment of diabetic cataract, cancer and arteriosclerosis obliterans and as a tonic for stomach nourishment, saliva secretion promotion and fever reduction. However, few studies have been carried out on its in vivo metabolism. In the present study, a rapid and sensitive method based on ultra-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-Q/TOF-MS) in positive ion mode was developed and applied to identify the metabolites of gigantol in rat urine after a single oral dose (100 mg/kg). Chromatographic separation was performed on an Acquity UPLC HSS T3 column (100 × 2.1 mm i. d., 1.8 µm) using acetonitrile and 0.1% aqueous formic acid as mobile phases. A total of 11 metabolites were detected and identified as all phase II metabolites. The structures of the metabolites were identified based on the characteristics of their MS, MS(2) data and chromatographic retention times. The results showed that glucuronidation is the principal metabolic pathway of gigantol in rats. The newly identified metabolites are useful to understand the mechanism of elimination of gigantol and, in turn, its effectiveness and toxicity. As far as we know, this is the first attempt to investigate the metabolic fate of gigantol in vivo.

In vivo and in vitro metabolism of trans-resveratrol by human gut microbiota.

BACKGROUND: Strong interindividual differences in the microbial conversion of some dietary polyphenols have been reported. In-depth studies of trans-resveratrol metabolism by human gut microbiota, however, are lacking, and only one bacterial metabolite, namely dihydroresveratrol, has been described. OBJECTIVE: The aim of this study was to elucidate interindividual differences in trans-resveratrol metabolism by human gut microbiota and to identify bacterial strains involved. DESIGN: In the first part of the study, in vitro fermentation experiments were performed with feces samples from 7 healthy volunteers, and metabolite formation was measured by liquid chromatography-ultraviolet/visible (UV/Vis)-mass spectrometry (MS)/MS detection. Microbial diversities in 3 feces samples were analyzed by high-throughput pyrosequencing and quantitative real-time polymerase chain reaction. In addition, trans-resveratrol conversion experiments were conducted with selected fecal bacterial strains in pure culture. The second part of the study was a controlled intervention study with 12 healthy volunteers. After a washout period, all of the subjects received a one-time oral dose of 0.5 mg trans-resveratrol/kg body weight in the form of a grapevine-shoot supplement, and 24-h urine samples were analyzed by liquid chromatography-UV/Vis-MS/MS. RESULTS: Besides dihydroresveratrol, 2 previously unknown bacterial trans-resveratrol metabolites were identified in vitro and in vivo: 3,4'-dihydroxy-trans-stilbene and 3,4'-dihydroxybibenzyl (lunularin). Their formation, however, varied among the volunteers. Two strains, Slackia equolifaciens and Adlercreutzia equolifaciens, were identified as dihydroresveratrol producers. Gut bacteria able to produce dehydroxylated metabolites could, however, not be identified. CONCLUSIONS: trans-Resveratrol metabolism by human gut microbiota shows pronounced interindividual differences, which should be taken into account during investigation of health-related effects of this stilbene. This trial was registered at the German Clinical Trials Register as DRKS00004311, Universal Trial Number (WHO) UTN: U1111-1133-4621.