Model system-based mechanistic studies of black tea thearubigin formation.

Thearubigins are the most abundant pigments found in black tea, comprising polyphenolic oxidation products, whose composition and chemical nature have remained unresolved until recently. In the course of studying the mechanism of thearubigin formation from green tea flavan-3-ols, a model system, based on electrochemical oxidation of one of the main tea flavan-3-ol substrates, epigallocatechin gallate (EGCG), was employed. Reaction intermediates and products were subsequently analysed using mass spectrometry techniques, allowing for the identification of key intermediates and products.

Identification of novel homologous series of polyhydroxylated theasinensins and theanaphthoquinones in the SII fraction of black tea thearubigins using ESI/HPLC tandem mass spectrometry.

Thearubigins are the most abundant phenolic pigments found in black tea, produced by enzymatic oxidation of green tea flavan-3-ols in tea fermentation of until recently unknown composition. In this study electrospray ionization tandem LC-MS(n) experiments have been applied for the characterization of crude thearubigins isolated from black tea not exceeding 1000 Da. The aim of this study is to confirm the oxidative cascade hypothesis of tea fermentation.