Abstract
Caffeic acid as well as its oxidation products exert a spectrum of biological effects
in in vitro testing. To get an idea of the amount as well as the mode of biotransformation, caffeic
acid metabolism was investigated by means of the isolated perfused rat liver. The
first-pass effect was not pronounced: 93.3% of caffeic acid dose appeared unchanged
after one liver passage. Products of caffeic acid oxidation (cyclolignan derivatives)
as well as ferulic and isoferulic acid as methylation products were found in the perfusion
medium. In addition, a cyclization product, esculetin, was observed. In the bile,
mainly glucuronides as well as sulfates of caffeic acid could be determined. Thus,
oxidation products and other metabolites formed by liver metabolism can be responsible
for the biological effects in vivo.
Key words
Caffeic acid - cyclolignan derivatives - coumarins - isolated perfused rat liver -
hepatic metabolism
