Abstract
Extra virgin olive oil (EVOO) polyphenols beneficial effects have widely been debated throughout the last three decades, with greater attention to hydroxytyrosol and tyrosol, which are by far the most studied. The main concern about the evaluation of EVOO phenols activities in vitro and in vivo is that the absorption and metabolism of these compounds once ingested lead to the production of different metabolites in the human body. EVOO phenols in the ingested forms are less concentrated in human tissues than their glucuronide, sulfate and methyl metabolites; on the other hand, metabolites may undergo deconjugation before entering the cells and thus act as free forms or may be reformed inside the cells so acting as conjugated forms. In most in vitro studies the presence of methyl/sulfate/glucuronide functional groups does not seem to inhibit biological activity. Parent compounds and metabolites have been shown to reach tissue concentrations useful to exert beneficial effects others than antioxidant and scavenging properties, by modulating intracellular signaling and improving cellular response to oxidative stress and pro-inflammatory stimuli. This review aims to give an overview on the reported evidence of the positive effects exerted by the main EVOO polyphenols metabolites in comparison with the parent compounds.
Highlights
The consumption of extra virgin olive oil (EVOO) is feature of the Mediterranean Diet, which has been largely associated to several health benefits [1,2,3,4]
In relation to a protective role at gastrointestinal level, we showed in Caco-2 cells monolayers that HT, Tyr and homovanillyl alcohol were able to protect cell membranes from oxidative damage induced by tert-butil hydroperoxide (TBH) treatments [75]
The same activities were observed in the same cell line treated with another EVOO metabolite which is similar in structure to luteolin 7-O-glucuronide, apigenin-7-O-glucuronide [91,92], which showed to be effective in counteracting prostaglandin E2 (PGE2) production, LPS-induced mRNA expression of iNOS, cyclooxygenase-2 (COX-2), and TNF-α
Summary
The consumption of extra virgin olive oil (EVOO) is feature of the Mediterranean Diet, which has been largely associated to several health benefits [1,2,3,4]. Anti-cancer properties of EVOO polyphenols have been related to their interactions with proteins controlling cell cycle progression and gene expression [2,8,11,12,13] Their effectiveness in vivo, should be carefully evaluated taking into account the absorption and metabolism kinetics of these compounds once ingested. In the last decade more and more research groups centered their studies on the evaluation of how and to which extent major metabolites of EVOO polyphenols were able to modulate intracellular signals and exert antioxidant and scavenging capacities. Trying to give an overview of these activities, the present review will focus on the biological significance of major EVOO polyphenols metabolites, considering their effect in different in vitro and in vivo studies in comparison with their parent compounds
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