Feature-Based Molecular Networking Analysis of the Metabolites Produced by <i>In Vitro</i> Solid-State Fermentation Reveals Pathways for the Bioconversion of Epigallocatechin Gallate
Hao-Fen Xie, Ya-Shuai Kong, Ru-Ze Li, Louis‐Félix Nothias, Alexey V. Melnik, Hong Zhang, Lulu Liu, Tingting An, Rui Liu, Zi Yang, Jia‐Ping Ke, Peng Zhang, Guan‐Hu Bao, Zhongwen Xie, Daxiang Li, Xiaochun Wan, Qianying Dai, Liang Zhang, Ming Zhao, Mao-Qiang An, Yanhua Long, Tie-Jun Ling
Abstract
Dark teas are prepared by a microbial fermentation process. Flavan-3-ol B-ring fission analogues (FBRFAs) are some of the key bioactive constituents that characterize dark teas. The precursors and the synthetic mechanism involved in the formation of FBRFAs are not known. Using a unique solid-state fermentation system with β-cyclodextrin inclusion complexation as well as targeted chromatographic isolation, spectroscopic identification, and Feature-based Molecular Networking on the Global Natural Products Social Molecular Networking web platform, we reveal that dihydromyricetin and the FBRFAs, including teadenol A and fuzhuanin A, are derived from epigallocatechin gallate upon exposure to fungal strains isolated from Fuzhuan brick tea. In particular, the strains from subphylum Pezizomycotina were key drivers for these B-/C-ring oxidation transformations. These are the same transformations seen during the fermentation process of dark teas. These discoveries set the stage to enrich dark teas and other food products for these health-promoting constituents.