Structural characterization of the metabolites of hydroxytyrosol, the principal phenolic component in olive oil, in rats

Kellie L. Tuck, Peter J. Hayball, Ieva Stupans

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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 by1H 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 SC50 values of 14.8 and 11.4 μM for homovanillic acid and homovanillic alcohol, respectively. The 3-O-glucuronide conjugate was more potent than hydroxytyrosol, with an SC50 of 2.3 in comparison to 11.0 μM, and the monosulfate conjugate was almost devoid of radical scavenging activity.

Original languageEnglish
Pages (from-to)2404-2409
Number of pages6
JournalJournal of Agricultural and Food Chemistry
Issue number8
Publication statusPublished - 10 Apr 2002
Externally publishedYes


  • Antioxidant activity
  • Hydroxytyrosol
  • Mediterranean diet
  • Metabolites
  • Olive oil

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