Transport mechanism and metabolism of olive oil hydroxytyrosol in Caco-2 cells

3,4-Dihydroxyphenylethanol (hydroxytyrosol; DPE) is the major phenolic anti oxidant present in extra virgin olive oil, either in a free or esterified f orm. Despite its relevant biological effects, no data are available on its bioavailability and metabolism. The aim of the present study is to examine the molecular mechanism of DPE intestinal transport, using differentiated C aco-2 cell monolayers as the model system. The kinetic data demonstrate tha t [C-14]DPE transport occurs via a passive diffusion mechanism and is bidir ectional; the calculated apparent permeability coefficient indicates that t he molecule is quantitatively absorbed at the intestinal level. The only la belled DPE metabolite detectable in the culture medium by HPLC (10% convers ion) is 3-hydroxy-4-methoxyphenylethanol, the product of catechol-O-methylt ransferase; when DPE is assayed in vitro with the purified enzyme a K-m val ue of 40 mu M has been calculated. (C) 2000 Federation of European Biochemi cal Societies.