It is well know that green tea polyphenols have a beneficial health effect, which is primarily accounted to the presence of catechins. There is abundant knowledge about the metabolites of these substances that appear in urine and plasma after green tea ingestion, but there is not much known on their degradation in the intestine.

Markus Schantz, Thomas Erk and Elke Richling from Kaiserlautern, Germany, have studied the metabolism of the normal human gut microbes and chemical stability of these polyphenols in the intestine. They use a very clever, established and ex vivo model: Fresh ileal fluids (obtained from volunteers with terminal ileostomies) were incubated for 24 h under anaerobic conditions with different catechins, i.e., (+)-catechin (C), (–)-epicatechin (EC), (–)-epicatechin 3-O-gallate (ECG), (–)-epigallocatechin (EGC), (–)-epigallocatchin 3-O-gallate (EGCG), and gallic acid (GA). Then, the metabolites were analysed by HPLC-photodiode array detection and tandem mass spectrometry.

Interestingly the same metabolites were detected, although the microbiota of the probands that were also characterized were substantially different.
The authors conclude that microbiota-dependent liberation of the metabolites occurs before these compounds reach the colon.

Photo: (C) PhotoDisc, Inc./Getty Images

• Metabolism of green tea catechins by the human small intestine,
  Markus Schantz, Thomas Erk, Elke Richling
  Biotech. J. 2010, 5, 1050–1059.
  DOI: 10.1002/biot.201000214