Metabolism of polyphenols from dietary exposure to urinary metabolites

Plant polyphenols are bioactive compounds which have been studied intensively. Polyphenol intake has been associated with reduced risk of cardiovascular disease and diabetes. In addition to health effects, also the metabolism of polyphenols has been investigated. After the intake, a small amount of the ingested polyphenols is converted to different conjugates by the enzymes of intestinal tissues, and enters the bloodstream. Furthermore, polyphenols can be further metabolized in the liver. In addition, extensive microbial transformations of polyphenols by colonic microbiota have been detected. However, the roles of colonic and post-colonic hepatic metabolism of polyphenols have remained unclear.

The aims of this study were:

  1. Clinical trial (in vivo*): phenolic metabolism was studied in a clinical trial. Altogether, 72 obese subjects with a high cardiovascular and metabolic risk profile participated in the trial. They followed a high-polyphenol diet or low-polyphenol control diet for 8 weeks. At baseline and after the intervention all subjects collected 24h-urine.
  2. Colon model (in vitro): microbial phenolic metabolism was studied by using a colon model. Polyphenol-rich foods were subjected to human faecal microbiota.
  3. Hepatocyte model: (in vitro): the role of liver on post-colonic metabolism of polyphenols was explored in a hepatocyte model. Metabolites from green tea were incubated with hepatocytes to highlight hepatic conversion of polyphenols.

In vivo refers to a study on whole, living organism. In vitro studies are carried out in a laboratory environment using test tubes, petri dishes etc.


A significant correlation was found between urinary (clinical trial) and colonic (in vitro) metabolites. However, higher amounts of hippuric acid, 3-hydroxybenzoic acid and ferulic acid were detected in urine than in the colon model. Also hepatocyte model showed additional amounts of these metabolites. According to results, combining in vitro colon and hepatic models may better elucidate the metabolism of polyphenols from dietary exposure to urinary metabolism. The study showed that the polyphenol metabolism is partly due to microbial conversion and partly by post-colonic hepatic conversions.

Anni Koskela, Arctic Flavours Association
+358 40 164 6177


polyfenolit  aineenvaihdunta  fenolinen hiiliketju  ruuansulatusmalli  maksasolut  polyphenols  metabolism  phenolic carbon backbone  in vitro colon model  primary hepatocytes