**1. Introduction**

286 Olive Germplasm – The Olive Cultivation, Table Olive and Olive Oil Industry in Italy

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A large mass of research has been accumulating to provide evidence for the health benefits of olive oil feeding and to scientifically support the widespread adoption of traditional Mediterranean diet as a model of healthy eating (Menendez *et al.*, 2007). This evidence has been attributed to the fact that olive oil, the predominant source of fat in the Mediterranean diet (Petroni *et al.*, 1995), contains several minor non-nutrients chemicals such as α- and γtocopherols and β-carotene, phytosterols, pigments, terpenic acids, flavonoids such as luteolin and quercetin, squalene, and phenolic compounds, usually and incorrectly termed polyphenols (Menendez *et al.*, 2007; Visioli *et al.*, 2002; Trichopoulou *et al.*, 2003; Tripoli *et al.*, 2005; Servili *et al.*, 2004). The main phenolic compounds in virgin olive oil are secoiridoid derivatives of 2-(3,4-dihydroxyphenyl)ethanol (3,4-DHPEA) and 2-(4-hydroxyphenyl) ethanol (*p*-HPEA) that occur as either simple phenols or esterified with elenolic acid to form, respectively, oleuropein and its derivative demethyloleuropein, and ligstroside, their aglycones 3,4-DHPEA-EA and *p*-HPEA-EA (Figure 1) (Bendini *et al.*, 2007; Suárez *et al.*, 2009). The aglyconic form of oleuropein and ligstroside, 3,4-DHPEA-EA and *p*-HPEA-EA respectively, were reported for the first time by Montedoro et al, who also assigned their chemical structures, later confirmed by other (Montedoro *et al.*, 1992; Angerosa *et al.*, 1996; Owen *et al.*, 2000). 3,4-DHPEA-EA and *p*-HPEA-EA, associated to the intense sensory of bitterness and pungency respectively attribute in VOO (Gutierrez-Rosales *et al.*, 2003), is endowed with numerous beneficial effects on human health (Servili *et al.*, 2004; Bendini *et al.*, 2007; Esti *et al.*, 1998; Della Ragione *et al.*, 2000; Paiva-Martins *et al.*, 2001; Fabiani *et al.*, 2002; Carasco-Pancorbo *et al.*, 2005; Artajo *et al.*, 2006; Fabiani *et al.*, 2006; Fabiani *et al.*, 2008; Paiva-Martins *et al.*, 2009).

© 2012 Britti et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Britti et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Oleuropein an Olive Oil Compound in Acute and Chronic Inflammation Models: Facts and Perspectives 289

steroidal drugs (NSAIDs). Therefore, carrageenan-induced local inflammation (pleurisy) is a useful model to assess the contribution of mediators involved in cellular alterations during the inflammatory process. In particular, the initial phase of acute inflammation (0-1h) which is not inhibited by NSAIDs such as indomethacin or aspirin, has been attributed to the release of histamine, 5-hydroxytryptamine and bradykinin, followed by a late phase (1-6 h) mainly sustained by prostaglandin release and attributed to the induction of inducible cyclo-oxygenase (COX-2) in the tissue (Nantel *et al.*, 1999). It appears that the onset of the carrageenan-induced acute inflammation has been linked to neutrophil infiltration and the production of neutrophil-derived free radicals, such as hydrogen peroxide, superoxide and hydroxyl radical, as well as the release of other neutrophil-derived mediators. Free radicals are produced in small amounts by normal cellular processes as part of the mitochondrial electron transport chain and the microsomal cytochrome P-450 system. They are formed during traumatic or hypoxic injuries as a consequence of insufficient oxygenation. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) can react with and subsequently damage proteins, nucleic acids, lipids, and extracellular matrix proteins. During the inflammatory response, ROS and RNS modulate phagocytosis, secretion, gene expression, and apoptosis. Indeed, under pathological circumstances such as acute lung injury and sepsis, excess production of neutrophil-derived ROS and RNS may influence neighbouring endothelial or epithelial cells, contributing to the amplification of inflammatory tissue injury (Fialkow *et al.*, 2007). Furthermore, oxidative stress elicits the activation of the redox-sensitive transcription factors such as nuclear factor-κB (NF-κB) and AP-1, that play a central and crucial role in inducing the expression of inflammatory cytokines and intercellular adhesion molecule (ICAM-1) (Chen *et al.*, 2004) and the activation of the redox-sensitive protein kinases such as the mitogen-activated protein kinase (MAPK) superfamily (Li *et al.*, 2002). Thus, the study model was designed to evaluate the effects of 3,4-DHPEA-EA in a mice model of acute inflammation (0.1 ml of saline containing 2% λcarrageenan was injected into the pleural cavity). In particular, we investigated the effects of 3,4-DHPEA-EA on the lung injury associated with carrageenan induced pleurisy. In order to gain a better insight into the mechanism of action of 3,4-DHPEA-EA, we have also investigated the effects on: 1) lung damage (histology), 2) polymorphonuclear (PMN) infiltration (myeloperoxidase [MPO] activity), 3) ICAM-1 and platelet-adhesion-molecule (P-selectin) expression, 4) nitrotyrosine and poly-ADP-ribose (PAR) formation, 5) proinflammatory cytokines production, tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), 6) lipid peroxidation (malondialdehyde [MDA] levels), and 7) nitric oxide (NO)

*Animals* - Male CD mice, weight 20-25 g; Harlan Nossan, Milan, Italy, were used in these studies. The animals were housed in a controlled environment and provided with standard rodent chow and water. Animal care was in compliance with Italian regulations on the protection of animals used for experimental and other scientific purposes (D.lgs 116/92) as

synthesis (nitrite-nitrate concentration).

well as with EEC regulations (O.J. of E.C. L358/1 12/18/1986).

**2.1. Materials and methods** 

**Figure 1.** Chemical structures.

In particular, the anti-inflammatory properties of olive oil phenolic compounds seem to overlap with those attributed to non-steroidal anti-inflammatory drugs (Procopio A, *et al.*, 2009). The majority of phenolic compounds found in olive oil or table olives are derived from the hydrolysis of oleuropein, the major phenolic constituent of the leaves and unprocessed olive drupes of *Olea europaea* and responsible for the bitter taste of immature and unprocessed olives. Concentrations of up to 9.0 mg/l of oleouropein and 5.6 mg/l of its hydrolysis product hydroxytyrosol, have been detected in some preparations of olive oil (Montedoro *et al.*, 1992). Oleuropein, a glucoside with hydroxyaromatic functionality, has recognized several pharmacological properties including antioxidant, anti-inflammatory, anti-atherogenic, anti-cancer, antidiabetic, antimicrobial, and antiviral, and for these reasons, it is commercially available as food supplement in Mediterranean countries (Miles *et al.*, 2005; Covas, 2008; Omar, 2010). A more efficient anti-inflammatory role of the aglyconic 3,4-DHPEA-EA compared with the glycosidic form of oleuropein possibly derives from the greater lipophilicity of the former, a property that should allow better cell membrane incorporation and/or interaction with other lipids (Saija *et al.*, 1998). We focused on the antinflammatory properties of 3,4-DHPEA-EA, a hydrolysis product obtained from Oleuropein by the action of β-glucosidase on the parent glucoside, has been evaluated in a mice model of acute inflammation (carrageenan-induced pleurisy) and in a mice model of chronic inflammation (collagen-induced arthritis) (Impellizzeri *et al.*, 2011a-b).
