Feature-Based Molecular Networking Analysis of the Metabolites Produced by in vitro Solid-State Fermentation Reveals Pathways for the Bioconversion of Epigallocatechin Gallate

Flavan-3-ol B-ring fission derivatives (FBRFDs) are secondary metabolites that contribute to the unique properties of fermented dark teas. However, the FBRFD precursors and biochemistry are unclear. Fungal strains cultured from Fuzhuan brick tea (FBT) were incubated in an in vitro solid-state fermentation system containing β-cyclodextrin-embedded epigallocatechin gallate (EGCG), a potential precursor of FBRFDs. The produced metabolites were analyzed through a combination of targeted chromatographic isolation, non-targeted spectroscopic identification, and Feature-based Molecular Networking (FBMN) in the Global Natural Products Social Molecular Networking (GNPS) platform. Dihydromyricetin was identified for the first time, indicating that fungi possess a flavan-3-ol C-ring oxidation pathway. EGCG was verified as the precursor of dihydromyricetin and FBRFDs such as teadenol A and fuzhuanin A. The conversion was driven by the fungi rather than a hygrothermal effect. Isolates from Pezizomycotina showed much stronger abilities to convert EGCG to the B-/C-ring oxidation products than those from Saccharomycotina or Basidiomycota.

Feature-Based Molecular Networking Analysis of the Metabolites Produced by in vitro Solid-State Fermentation Reveals Pathways for the Bioconversion of Epigallocatechin Gallate

Flavan-3-ol B-ring fission derivatives (FBRFDs) are secondary metabolites that contribute to the unique properties of fermented dark teas. However, the FBRFD precursors and biochemistry are unclear. Fungal strains cultured from Fuzhuan brick tea (FBT) were incubated in an in vitro solid-state fermentation system containing β-cyclodextrin-embedded epigallocatechin gallate (EGCG), a potential precursor of FBRFDs. The produced metabolites were analyzed through a combination of targeted chromatographic isolation, non-targeted spectroscopic identification, and Feature-based Molecular Networking (FBMN) in the Global Natural Products Social Molecular Networking (GNPS) platform. Dihydromyricetin was identified for the first time, indicating that fungi possess a flavan-3-ol C-ring oxidation pathway. EGCG was verified as the precursor of dihydromyricetin and FBRFDs such as teadenol A and fuzhuanin A. The conversion was driven by the fungi rather than a hygrothermal effect. Isolates from Pezizomycotina showed much stronger abilities to convert EGCG to the B-/C-ring oxidation products than those from Saccharomycotina or Basidiomycota.

Feature-Based Molecular Networking Analysis of the Metabolites Produced by in vitro Solid-State Fermentation Reveals Pathways for the Bioconversion of Epigallocatechin Gallate

Flavan-3-ol B-ring fission derivatives (FBRFDs) are secondary metabolites that contribute to the unique properties of fermented dark teas. However, the FBRFD precursors and biochemistry are unclear. Fungal strains cultured from Fuzhuan brick tea (FBT) were incubated in an in vitro solid-state fermentation system containing β-cyclodextrin-embedded epigallocatechin gallate (EGCG), a potential precursor of FBRFDs. The produced metabolites were analyzed through a combination of targeted chromatographic isolation, non-targeted spectroscopic identification, and Feature-based Molecular Networking (FBMN) in the Global Natural Products Social Molecular Networking (GNPS) platform. Dihydromyricetin was identified for the first time, indicating that fungi possess a flavan-3-ol C-ring oxidation pathway. EGCG was verified as the precursor of dihydromyricetin and FBRFDs such as teadenol A and fuzhuanin A. The conversion was driven by the fungi rather than a hygrothermal effect. Isolates from Pezizomycotina showed much stronger abilities to convert EGCG to the B-/C-ring oxidation products than those from Saccharomycotina or Basidiomycota.

Function of Green Tea Catechins in the Brain: Epigallocatechin Gallate and its Metabolites

Over the last three decades, green tea has been studied for its beneficial effects, including anti-cancer, anti-obesity, anti-diabetes, anti-inflammatory, and neuroprotective effects. At present, a number of studies that have employed animal, human and cell cultures support the potential neuroprotective effects of green tea catechins against neurological disorders. However, the concentration of (−)-epigallocatechin gallate (EGCG) in systemic circulation is very low and EGCG disappears within several hours. EGCG undergoes microbial degradation in the small intestine and later in the large intestine, resulting in the formation of various microbial ring-fission metabolites which are detectable in the plasma and urine as free and conjugated forms. Recently, in vitro experiments suggested that EGCG and its metabolites could reach the brain parenchyma through the blood–brain barrier and induce neuritogenesis. These results suggest that metabolites of EGCG may play an important role, alongside the beneficial activities of EGCG, in reducing neurodegenerative diseases. In this review, we discuss the function of EGCG and its microbial ring-fission metabolites in the brain in suppressing brain dysfunction. Other possible actions of EGCG metabolites will also be discussed.

LC-MS Identification of Proanthocyanidins in Bark and Fruit of six Terminalia species

Proanthocyanidins (PAs) are the most important and valuable polyphenolic compounds of Terminalia species (family Combretaceae) used for the treatment of several diseases. This study aims to seek identification and characterization of PAs in the ethanolic extracts of bark and fruit of six Terminalia species viz T. arjuna, T. bellerica, T. catappa, T. chebula, T. elliptica and T. paniculata. A high performance liquid chromatography with quadrupole time-of-flight tandem mass spectrometry (HPLC/ESI-QTOF-MS/MS) method was developed for the simultaneous identification and characterization of PAs. The chromatographic separation was carried on a Thermo Betasil C8 column (250 mmx4.5 mm, 5μm) operated with 0.1% formic acid aqueous solution and acetonitrile as the mobile phase. The MS/MS fragmentation study of [M-H]- ions obtained from these PAs showed distinguishable fragment ions with high mass accuracy. Heterocyclic ring fission (HRF), retro-Diels-Alder (RDA) fragmentation, quinone methide (QM) fragmentation and benzofuran formation (BFF) have been identified as the characteristic fragments. Total of 51 PAs were tentatively identified which include 28 dimers, 15 trimers and 8 other flavan-3-ols.

Substrate-dependent aromatic ring fission of catechol and 2-aminophenol with O2catalyzed by a nonheme iron complex of a tripodal N4ligand

An iron(ii)–acetonitrile complex of a tripodal N4ligand catalyzes the O2-dependent aromatic ring fission of catechol and 2-aminophenolviaintradiol and extradiol pathway, respectively.