**2. Bioavailability of olive oil polyphenols**

Accumulating evidence suggests that VOO may have health benefits; it can be considered as an example of a functional food containing a variety of components that may contribute to its overall therapeutic characteristics (Stark & Madar, 2002; Visioli & Bernardini, 2011). To explore and determine the mechanisms of action of olive oil polyphenols and their role in disease prevention, understanding the factors that constrain their release from the olive oil, their extent of absorption, and their fate in the organism is crucial. These issues can be described under the term *bioavailability,* borrowed from the field of pharmacology, redefined as "that fraction of an oral dose, either parent compound or active metabolite, from a particular preparation that reaches the systemic circulation" (Stahl et al., 2002). To simplify this definition, D'Archivio et al. (2010) explained that it simply means how much of the

techniques used and the pedoclimatic conditions are the aspects more extensively studied (Tovar et al., 2001; Uceda et al., 1999). Moreover, by modulating technology, it is possible to some extent to optimize the transfer of some polar minor constituents into the oil or reduce their level (Boskou, 2009). The influence of variety, extraction system, ripening degree and storage in the polyphenolic content of a VOO has been extensively discussed in the

Wide ranges of total polar phenols concentration have been reported in olive oils (50-1000 mg/kg), although the most usual value is found between 100-350 mg/kg (Boskou et al., 2006). In general, the most abundant phenolic compounds in VOO are aglycones deriving from secoiridoids. Trying to establish levels of individual phenols, Servili & Montedoro (2002) calculated average values of 7 phenolic compounds from a considerable number of samples of industrial olive oils. They concluded that Hyty and Ty were found only in trace amounts (less than 10 mg/kg oil) and the most abundant phenols were decarboxylated Ol Agl (63-840 mg/kg), Ol Agl (85–310 mg/kg), and decarboxylated Lig Agl (15-33 mg/kg). Brenes et al. (2002) published values ranging from 3-67 mg/kg for 1-acetoxypinoresinol, and from 19-41 mg/kg for pinoresinol in 5 Spanish olive oils, data that can be completed with the researches carried out by Romero et al. (2002) and Tovar et al. (2001). Levels of luteolin have been found to be around 10 mg/kg in some Spanish olive oils (Brenes et al., 1999) or ranging between 0.2-7 mg/kg for Greek oils (Murkovic et al., 2004). Carrasco-Pancorbo et al. (2006) developed a method to quantify 14 individual phenols belonging to different families in 7 Spanish extra-virgin olive oils (EVOOs). They also quantified them, finding the following contents (mg/kg): simple phenols: 6.8-11.5; complex phenols: 70.5-799.5; lignans:

Intake of olive oil in the Mediterranean countries is estimated to be 30–50 g/day, based on the per capita olive oil consumption of 10–20 kg/year in Greece, Italy and Spain (Boskou, 2000; Food and Agricultural Organization, 2000). A daily consumption of 50 g olive oil with a concentration of 180 mg/kg of phenols would result in an estimated intake of about 9 mg of olive oil phenols per day (de la Torre, 2008; Vissers et al., 2004), of which at least 1 mg is derived from free Hyty and Ty, and 8 mg are related to their elenolic esters and also to Ol Agl and Lig Agl (de la Torre, 2008). Some other estimations have been made. For the Greek population (Dilis & Trichopolou, 2009), the daily per-capita intake is about 17 mg. Vissers et al. (2004) estimated that about 1 mg of the phenol intake per day (6 mmol) is derived from Hyty and Ty, about 8 mg (23 mmol) from the aglycones, and so the total phenol intake

Accumulating evidence suggests that VOO may have health benefits; it can be considered as an example of a functional food containing a variety of components that may contribute to its overall therapeutic characteristics (Stark & Madar, 2002; Visioli & Bernardini, 2011). To explore and determine the mechanisms of action of olive oil polyphenols and their role in disease prevention, understanding the factors that constrain their release from the olive oil, their extent of absorption, and their fate in the organism is crucial. These issues can be described under the term *bioavailability,* borrowed from the field of pharmacology, redefined as "that fraction of an oral dose, either parent compound or active metabolite, from a particular preparation that reaches the systemic circulation" (Stahl et al., 2002). To simplify this definition, D'Archivio et al. (2010) explained that it simply means how much of the

literature (Boskou, 2009; Uceda et al., 1999).

0.81-20.6; and flavonoids: 1.4-8.6.

would be about 29 mmol.

**2. Bioavailability of olive oil polyphenols** 

ingested amount of polyphenols is able to exert its beneficial effects in the target tissues. It is important to realize that the most abundant phenolic compounds in our diet are not necessarily those that have the best bioavailability profile, either because they have a lower intrinsic activity or because they are poorly absorbed from the intestine, highly metabolized, or rapidly eliminated. In addition, the metabolites that are found in blood and target organs, resulting from digestive or hepatic activity, may differ from the native compounds in terms of biological activity (Manach et al., 2004).

Although the information concerning the bioavailability of most olive oil polyphenols is limited, intensive research has been carried out in the past decade. This fact is reflected in the number of reviews published since 2002 (Corona et al., 2009; Covas et al., 2009; de la Torre, 2008; Fitó et al., 2007; Tuck & Hayball, 2002; Visioli et al., 2002; Vissers et al., 2004). To address the bioavailability of olive oil phenolic compounds, we have reviewed *in vitro* and *in vivo (*both animal and human) studies on the absorption, transport, metabolism and excretion of olive oil phenolic compounds.
