The In Vivo Fate of Hydroxytyrosol and Tyrosol, Antioxidant Phenolic Constituents of Olive Oil, after Intravenous and Oral Dosing of Labeled Compounds to Rats

Abstract

In vitro studies have shown phenolics in olive oil to be strong radical scavengers. The absorption and elimination of two radiolabeled phenolic constituents of olive oil, hydroxytyrosol and tyrosol were studied in vivo using rats. Compounds were administered intravenously (in saline) and orally (in oil-and water-based solutions). For both compounds, the intravenously and orally administered oil-based dosings resulted in significantly greater elimination of the phenolics in urine within 24 h than the oral, aqueous dosing method. There was no significant difference in the amount of phenolic compounds eliminated in urine between the intravenous dosing method and the oral oil-based dosing method for either tyrosol or hydroxytyrosol. Oral bioavailability estimates of hydroxytyrosol when administered in an olive oil solution and when dosed as an aqueous solution were 99% and 75%, respectively. Oral bioavailability estimates of tyrosol, when orally administered in an olive oil solution and when dosed as an aqueous solution were 98% and 71%, respectively. This is the first study that has used a radiolabeled compound to study the in vivo biological fates of hydroxytyrosol and tyrosol.

Bioavailability and antioxidant effects of olive oil phenols in humans: a review

“…We found 13 publications that addressed absorption, metabolism, or urinary excretion of olive oil phenols: five animal (Bai et al, 1998;Coni et al, 2000;D'Angelo et al, 2001;Tuck et al, 2001;Visioli et al, 2001), six human studies (Bonanome et al, 2000;Visioli et al, 2000a, b;Miro-Casas et al, 2001a, b;Vissers et al, 2002), and two studies that addressed characterisation of the metabolites of hydroxytyrosol in urine from two of the above-mentioned studies Tuck et al, 2002). One study by our group showed that apparent in vivo absorption of the ingested olive oil phenols was more than 55-66 mol% in humans.…”

“…One study by our group showed that apparent in vivo absorption of the ingested olive oil phenols was more than 55-66 mol% in humans. A study in rats showed that bioavailability of radiolabelled tyrosol and hydroxytyrosol was 71-99% compared to intravenously administered tyrosol and hydroxytyrosol (Tuck et al, 2001). Eight studies showed that of the total amount of ingested phenols, at least 5% was excreted in urine as tyrosol and hydroxytyrosol (Visioli et al, 2000a(Visioli et al, , b, 2001D'Angelo et al, 2001;Miro-Casas et al, 2001a, b;Tuck et al, 2001;Vissers et al, 2002), mainly as glucuronide (Visioli et al, 2000b;Miro-Casas et al, 2001a, b;Tuck et al, 2002) and monosulphate conjugates (D'Angelo et al, 2001;Tuck et al, 2002), and in the O-methylated form as homovanillic alcohol and homovanillic acid (Visioli et al, 2000a;Caruso et al, 2001;D'Angelo et al, 2001;Tuck et al, 2002).…”

Phenolic Molecules in Virgin Olive Oils: a Survey of Their Sensory Properties, Health Effects, Antioxidant Activity and Analytical Methods. An Overview of the Last Decade Alessandra

“…In a later study, the same authors [59] noticed that the urinary levels of unconjugated tyrosol and hydroxytyrosol correlated with their intake, except at the highest dose, which increased the quantity of glucuronide conjugate. Tuck et al investigated the in vivo fate of hydroxytyrosol and tyrosol after intravenous and oral dosing of these tritium labelled compound to rats [60]. No significant differences in the amount of phenolic compounds eliminated in urine between the intravenous dosing method and the oral oil-based dosing method for either tyrosol or hydroxytyrosol were found.…”

Metabolism and Bioavailability of Olive Oil Polyphenols

“…In all of the investigated tissues, Hyty was enzymatically converted in oxidized and/or methylated derivatives, whereas the major urinary products were sulfo-conjugates. Tuck et al (2001) compared the elimination of Hyty and Ty in rat urine within 24 h after administration, both orally (in oil-and water-based solutions) and intravenously (in saline). When orally administrated, polyphenols will be subjected to first-pass metabolism, so that the contribution of intestinal metabolism will be quite relevant.…”

“…This was supported by finding that 15% of an Ol glycoside supplement administered to healthy human subjects was excreted in urine as Hyty and Ty. Tuck et al (2001) investigated the in vivo fate of tritium labeled Hyty and Ty after intravenous (in saline, tail vein) and oral dosing (in oil-and water-based solutions) to rats. For both Hyty and Ty, the elimination of radioactivity in urine within 24 h for the intravenously and orally administered oil-based dosing was significantly greater (95 and 75%, respectively) than the oral aqueous dosing method (74 and 53%, respectively).…”