Work

Aspergillus species and gut microbiota-mediated biotransformation of epigallocatechin gallate: From dark tea fermentation to intestinal metabolism

Year: 2026

Type: article

Abstract: : Epigallocatechin gallate (EGCG) is the most abundant and bioactive compound in tea, but its microbial biotransformation and mechanisms in vitro and in vivo remain unclear. Here, we investigated metabolisms of EGCG and dark tea by Aspergillus cristatus and A. niger , alongside EGCG biotransformation in rat intestines and in vitro gut microbiota. Epigallocatechin-(4β→8)-epicatechin 3,3'-digallate, epigallocatechin, oolongtheanin, and theasinensin B were among the EGCG-associated metabolites detected during fermentation by both fungi, whereas samarangenin A was detected as an early-stage EGCG-associated metabolite in A. cristatus fermentation. 3-Hydroxyflavone is a major late-stage EGCG-associated metabolite in A. cristatus , while A. niger produces a more complex array of metabolites. In liquid culture, A. cristatus showed faster EGCG disappearance than A. niger , whereas A. niger showed faster EGCG depletion in dark tea, indicating a substrate-dependent difference between the two fungi. The key intestinal transit window for EGCG in rats is 6-12 hours post-administration. In vitro , gut microbiota converted EGCG to monomeric catechins,while several sulfated catechin-related features were also detected. 16S rDNA sequencing revealed temporal changes in the relative abundances of dominant genera, including Ligilactobacillus, Lactobacillus, Streptococcus, and Escherichia-Shigella. This study lays the groundwork for optimizing dark tea fermentation and EGCG functional product development.

Source: Current Research in Food Science

DOI: 10.1016/j.crfs.2026.101587