Another class of flavonoids is represented by the colorless flavanols – more precisely, flavan-3-ols. They can be divided into monomers (catechins), dimers as well as polymers.
Monomers are:
- Catechin
- Gallocatechin
- Epicatechin
- Epigallocatechin
- Epicatechin gallate
- Epigallocatechin gallate
Dimers and polymers are:
- Theaflavine
- Thearubigine
- (Oligomeric) proanthocyanidins.
Flavanols are primarily found in tea, cocoa, fruits and beverages made from them. In addition to monomeric flavanols, plant foods also contain oligomeric flavanols such as the procyanidins in apples, dark chocolate and red wine. A more detailed description can be found on the page “Flavanols – Food”.
Several studies investigated the absorption rate of flavanols from green and black tea. Maximum plasma concentrations were determined after half an hour to 4 hours. Half of the flavanols were eliminated from the body after 1 to 6 hours. In this regard, the addition of milk to black tea did not affect absorption. A randomized clinical trial in 30 healthy subjects showed that, in particular, administration of green tea extract as a supplement – i.e., in tablet form – may provide benefits over tea drinking. Absorption was found to be higher in tablet form than when drinking green or black tea. In this regard, all forms of administration contained the same amount of epigallocatechin gallate. For flavanols, it was shown that only 1 to 2% of the orally absorbed amount was excreted with the basic structure preserved. This indicates a strong metabolization (metabolization).