Urinary excretion of olive oil phenols and their metabolites in humans

We have recently demonstrated, in humans, the bioavailability of hydroxytyr osol (3,4-dihydroxyphenylethanol; HT), one of the major antioxidant compone nts of virgin olive oil. In particular, we reported that this compound is p resent in lipoproteins involved in atherosclerotic processes and is excrete d in the urine mainly as glucuronide-conjugate. The aim of the present stud y was to elucidate, in humans, the metabolic fate of HT after ingestion of virgin olive oil. After administration of virgin olive oil, 24-hour urine c ollections of healthy volunteers were prepared for gas chromatography-mass spectrometry analyses in order to identify and quantify HT and its metaboli tes homovanillic alcohol (HVA1c) and homovanillic acid (HVA). The results i ndicate that this compound undergoes the action of catechol-O-methyl transf erase (COMT), enzymes involved in the catecholamine catabolism, resulting i n an enhanced excretion of HVA1c. We also found a significant increase of H VA, indicating an oxidation of the ethanolic residue of HT and/or of HVA1c in humans. The excretion of both metabolites significantly correlated with the dose of administered HT. Copyright (C) 2001 by WB. Saunders Company.