The role of gut microbiota on the metabolism of black tea theaflavins

Abstract

The main bioactive polyphenols in black tea are theaflavins, including theaflavin (TF), theaflavin‐3‐gallate (TF3G), theaflavin‐3¢‐gallate (TF3¢G), and theaflavin‐3,3¢‐digallate (TFDG). Theaflavins have been reported as anti‐inflammatory and cancer preventive agents in different in vitro and in vivo models. Because of the poor systemic bioavailability of theaflavins, it is still unclear how these compounds can exert their biological functions. Studies have shown that higher molecular weight polyphenols are metabolized by the microbiota and their metabolites may play an important role in chronic disease prevention. The objective of this study is to identify the microbial metabolites of theaflavins in mice and in humans. Purified TF and TFDG were oral gavaged to specific pathogen free (SPF) mice, germ free (GF) mice, and incubated with human fecal slurries in vitro. Microbial bioconversion was monitored using liquid chromatography/mass spectrometry (LC/MS) by analyzing the MSn (n = 1–3) spectra. Our results indicated that TFDG can be metabolized by gut microbiota to generate gallic acid, pyrogallol, TF, TF3G, and TF3'G, and TF can be further broke down to small molecular metabolites by gut microbiota. Furthermore, we used selective culturing techniques to probe which bacterial groups are responsible for theaflavins metabolism in vitro. Fecal bacteria from SPF‐born 129SvEv mice were anaerobically cultured on blood agar (non‐selective agar), MacConkey agar (selective for gram‐negatives; G−) and Columbia colistin and nalidixic acid agar (gram‐positives; G+). The cultures were then anaerobically incubated in fermentation media containing theaflavins, and the resulting metabolites were analyzed by LC/MS. Lactobacillus plantarum and Escherichia coli NC101 were similarly assessed for theaflavins fermentation abilities. Our results revealed that the G+ bacteria (including L. plantarum on its own) instead of G− bacteria (including E. coli NC101 on its own) were able to produce these metabolites.Support or Funding InformationThis work was supported by NIH R01 grant AT008623.