The polyphenols hydroxytyrosol (HT) and hydroxytyrosol acetate (HT-AC) were administered to rats in varying doses and compared with acetylsalicylic acid (ASA), a compound known to have beneficial effects in reducing platelet aggregation.
They concluded that “HT and HT-AC, when given orally to rats, inhibit platelet aggregation and that among the mechanisms involved in this effect are decreased thromboxane synthesis and increased nitric oxide production. These results may offer an explanation for the beneficial effects of VOO in preventing cardiovascular events and open new perspectives toward the potential use of these polyphenols as an alternative to ASA in the prevention of arterial thrombotic events.”
The effect of ASA on platelet aggregation was shown to concur with earlier studies.
Platelet aggregation, like the over-production of LDL (low-density lipoprotein) cholesterol, contribute to thrombotic events.
Inside the Mediterranean diet
The researchers sought to understand why the Mediterranean diet, which contains high levels of oils such as virgin olive oil, is effective in reducing cardiovascular risk.
Olive oil consumption has been associated with improved lipid and thrombotic profile, insulin-mediated glucose metabolism, blood pressure, hemostasis, endothelial function, inflammation, and oxidative stress.
The University of Malaga study, published in the Journal of Agricultural and Food Chemistry, found that HT-AC was a better fighter of platelet aggregation than HT.
“The ability of HT-AC to influence platelet activity has notable implications, because ASA is the drug used most widely throughout the world for prophylaxis against thromboembolism, owing to its antiplatelet effect,” the researchers wrote.
Dosage ranged from that expected to have little effect to one with an inhibiting effect. The range was above consumption levels in a regular olive oil-rich Mediterranean diet.
“However, olive oil contains a complex of polyphenols and other antioxidants, which may have synergistic effects, as shown earlier for their antioxidant action,” the researchers wrote. “This makes it advisable to use higher doses when each compound is used separately.”
ASA was tested in doses equivalent to oral treatment as prophylaxis against thrombotic events (75 mg/day for a body weight of 75kg), a moderately high dose (350 mg/day), and an anti-inflammatory dose in humans (750 mg/day).
All compounds were administered orally for seven days. Platelet synthesis of thromboxane synthesis was inhibited by up to 30 per cent for HT and 37 per cent by HT-AC at a dose of 100mg/kg per day.
The researchers noted that the ratio between prostacyclin and thromboxane was improved from 1.55 in the control group to 2.94 in rats treated with ASA, 1.72 in the HT group and 1.34 in the HT-AC group.
The high ASA ratio was found to be due to its role in inhibiting prostacyclin production.
“The implications of this finding merit attention because they provide evidence that these polyphenols inhibit platelet aggregation while sparing, to a large extent, prostacyclin synthesis, i.e., one of the main endogenous mechanisms that also inhibits platelet aggregation.”
The researchers noted the limitations of their study including the “differences in the pharmacokinetics of HT between rats and humans”.
They added: “Moreover, according to the pharmacokinetic parameters of HT in rats, an acute effect of HT or HT-AC cannot be ruled out and it must be due to its metabolites in our experimental conditions.”
It was suggested hydrolysis in the small intestine may improve the bioavailability of HT-AC.
Journal of Agricultural and Food Chemist
Vol. 56, No. 17, 2008, Pages 7872-7876.
“Effects of Hydroxytyrosol and Hydroxytyrosol Acetate Administration to Rats on Platelet Function Compared to Acetylsalicylic Acid”
Authors : Jose Antonio Gonzalez-Correa, MariaDolores Navas,
Javier Munoz-Marin, Mariana Trujillo, Juan Fernandez-Bolanos, and
Jose Pedro De La Cruz.