title: Structural characterization of the metabolites of hydroxytyrosol, the principal phenolic component in olive oil, in rats.
abstract: Hydroxytyrosol is quantitatively and qualitatively the principal phenolic antioxidant in olive oil. Recently it was shown that hydroxytyrosol and five metabolites were excreted in urine when hydroxytyrosol was dosed intravenously or orally in an olive oil solution to rats. The conclusive identification of three metabolites of hydroxytyrosol by MS/MS as a monosulfate conjugate, a 3-O-glucuronide conjugate, and 4-hydroxy-3-methoxyphenylacetic acid (homovanillic acid) has been established in this investigation. The structural configurations of the glucuronide conjugate and 4-hydroxy-3-methoxyphenylacetic acid were confirmed by (1)H NMR. The radical scavenging potencies of homovanillic acid, homovanillic alcohol, hydroxytyrosol, and the metabolites were examined with the radical 2,2-diphenyl-1-picrylhydrazyl. These studies showed them to be potent antioxidants with SC(50) values of 14.8 and 11.4 microM for homovanillic acid and homovanillic alcohol, respectively. The 3-O-glucuronide conjugate was more potent than hydroxytyrosol, with an SC(50) of 2.3 in comparison to 11.0 microM, and the monosulfate conjugate was almost devoid of radical scavenging activity.
authors.affiliation: Centre for Pharmaceutical Research, School of Pharmaceutical, Molecular and Biomedical Sciences, University of South Australia, Adelaide 5000, Australia. Kellie.Tuck@unisa.edu.au
authors.forename: Kellie L
authors.initials: KL
authors.lastname: Tuck
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hayball
authors.forename: Ieva
authors.initials: I
authors.lastname: Stupans
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000737:chemistry; D016166:Free Radical Scavengers; D020719:Glucuronides / Q000737:chemistry / Q000378:metabolism; D006719:Homovanillic Acid / Q000737:chemistry / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D000069463:Olive Oil; D010636:Phenols / Q000737:chemistry*; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism* / Q000652:urine; D010938:Plant Oils / Q000032:analysis*; D051381:Rats
chemical_list: D000975:Antioxidants; D016166:Free Radical Scavengers; D020719:Glucuronides; D000069463:Olive Oil; D010636:Phenols; D010938:Plant Oils; C005975:3,4-dihydroxyphenylethanol; D010626:Phenylethyl Alcohol; D006719:Homovanillic Acid