METABOLISM OF CAFFEIC ACID IN THE ISOLATED-PERFUSED RAT-LIVER

Caffeic acid as well as its oxidation products exert a spectrum of bio logical effects in in vitro testing. To get an idea of the amount as w ell as the mode of biotransformation, caffeic acid metabolism was inve stigated by means of the isolated perfused rat liver. The first-pass e ffect was not pronounced: 93.3 % of caffeic acid dose appeared unchang ed after one liver passage. Products of caffeic acid oxidation (cyclol ignan derivatives) as well as ferulic and isoferulic acid as methylati on products were found in the perfusion medium. In addition, a cycliza tion product, esculetin, was observed. In the bile, mainly.glucuronide s as well as sulfates of caffeic acid could be determined. Thus, oxida tion products and other metabolites formed by liver metabolism can be responsible for the biological effects in vivo.