Monomeric green tea catechin (GTC) and oligomeric, oxidized black tea phenolic (BTP) have shown promising health benefits, although GTC has been more extensively studied than BTP. We review the current knowledge on bioavailability, colonic transformation, and gut microbiota modulatory effects of GTC and BTP. As a result of their similar poor bioavailability in the small intestine and potentially similar metabolites upon colonic fermentation, it seems as if GTC and BTP have similar health effects, although it cannot be excluded that they have different gut microbiota modulatory effects and that BTP gives a poorer yield of bioactive phenolic metabolites upon colonic fermentation than GTC.
Interaction of tea
phenolics with gut microbiota may play an integral role in the health
benefits of these bioactive compounds, yet this interaction is not
fully understood. Here, the metabolic fate of epigallocatechin-3-gallate
(EGCG) and its impact on gut microbiota were integrally investigated
via
in vitro
fermentation. As revealed
by ultrahigh performance liquid chromatography hybrid quadrupole Orbitrap
mass spectrometry (UHPLC-Q-Orbitrap-MS), EGCG was promptly degraded
into a series of metabolites, including 4-phenylbutyric acid, 3-(3′,4′-dihydroxyphenyl)propionic
acid, and 3-(4′-hydroxyphenyl)propionic acid, through consecutive
ester hydrolysis, C-ring opening, A-ring fission, dehydroxylation,
and aliphatic chain shortening. Microbiome profiling indicated that,
compared to the blank, EGCG treatment resulted in stimulation of the
beneficial bacteria
Bacteroides
,
Christensenellaceae
, and
Bifidobacterium
. Additionally, the pathogenic
bacteria
Fusobacterium varium
,
Bilophila
, and
Enterobacteriaceae
were
inhibited. Furthermore, changes in concentrations of metabolites,
including 4-phenylbutyric acid and phenylacetic acid, were strongly
correlated with changes in the abundance of specific gut microbiota.
These reciprocal interactions between EGCG and gut microbiota may
collectively contribute to the health benefits of EGCG.
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