New dibenzotropolone derivatives characterized from black tea using LC/MS/MS

Area of Science:

• Food Chemistry
• Natural Product Chemistry
• Analytical Chemistry

Background:

• Theaflavins and thearubigins are key black tea pigments.
• Their formation is attributed to the oxidation of flavan-3-ols (catechins) during tea fermentation.

Purpose of the Study:

• To investigate the oxidation mechanisms of tea polyphenols.
• To identify new higher molecular weight polymers in black tea, particularly thearubigins.
• To elucidate the structures and origins of novel compounds.

Main Methods:

• Enzymatic synthesis using horseradish peroxidase and H(2)O(2).
• Liquid Chromatography/Electrospray Ionization-Mass Spectrometry/Mass Spectrometry (LC/ESI-MS/MS) for analysis and characterization.
• Mass Spectrometry (MS) and 2D Nuclear Magnetic Resonance (2D NMR) for structural elucidation.

Main Results:

• Three new dibenzotropolones (theadibenzotropolone A, B, C) and one new tribenzotropolone (theatribenzotropolone A) were synthesized.
• Theadibenzotropolone A and B represent the first identified benzotropolone-type trimers of catechins in black tea.
• The structures were confirmed via MS and 2D NMR analyses.
• The presence of these compounds in black tea was verified using LC/ESI-MS/MS.

Conclusions:

• The galloyl ester groups of theaflavins can oxidize to form di- or tri-benzotropolone skeletons.
• This oxidation pathway is significant for increasing the molecular size of thearubigins.
• The study provides new insights into the chemical transformations occurring during black tea production.