**2.3 Osteoporosis**

376 Olive Oil – Constituents, Quality, Health Properties and Bioconversions

middle of last century (Scheller, 1955; Perrinjaquet-Moccetti et al. 2008; Susalit et al., 2011), and, since then, the benefits of minor olive components have been extensively investigated

The antioxidant activity is the most studied property of olive phenolic compounds. The interest of hydroxytyrosol is based on its remarkable pharmacological and antioxidant activities. Reactive oxygen species, which are continuously being formed as a result of metabolic processes in the organism, may cause oxidation and damage of cellular macromolecules, and therefore, may contribute to the development of degenerative diseases, such as atherosclerosis, cancer, diabetes, rheumatoid arthritis and other

The high antioxidant efficiency of HT, attributed to the presence of the *o*-dihydroxyphenyl moiety, is due to its high capacity for free radical scavenging during the oxidation process and to its reducing power on Fe3+ (Torres de Pinedo et al., 2007). The antioxidant properties of the *o*-diphenols are associated with their ability to form intramolecular hydrogen bonds between the hydroxyl group and the phenoxy radical (Visioli et al., 1998); therefore, the catechol avoids the chain propagation by donating a hydrogen radical to alkylperoxyl

) formed in the initiation step of lipid oxidation (Scheme 1).

O

H

Scheme 1. Mechanism of free radical scavenging by hydroxytyrosol

OH O

Oxidation of low-density lipoproteins (LDLs) is a lipid peroxidation chain reaction, which is initiated by free radicals. It has been shown that hydroxytyrosol can inhibit LDL oxidation efficiently due to its capacity to scavenge peroxyl radicals (Arouma et al., 1998; Turner et al., 2005). Hydroxytyrosol reduces oxidation of the low-density lipoproteins carrying cholesterol (LDL-C), which is a critical step in the development of atherosclerosis and other cardiovascular diseases (Gonzalez-Santiago et al., 2010; Vázquez-Velasco et al., 2011); hydroxytyrosol has also a potential protective effect against oxidative stress induced by *tert*-

It has been reported that hydroxytyrosol enhances the lipid profile and antioxidant status preventing the development of atherosclerosis. This compound may also reduce the expression of vascular cell adhesion molecules (Carluccio et al., 2007) and inhibit platelet aggregation in rats (González-Correa et al., 2008a) and hypercholesterolaemia in humans

Numerous studies about the relationship between olive oil consumption and cancer prevention have been carried out (Pérez-Jiménez et al., 2005). Antioxidant compounds supplied in the diet can reduce the risk of cancer due to the fact that they can minimize DNA damage, lipid peroxidation and the amount of ROS generated (Omar, 2010a;

ROO ROOH ROO ROOH

OH

O

O OH

(Tripoli et al., 2005).

radicals (ROO·

HO

HO

**2.1 Antioxidant activity** 

inflammatory diseases (Balsano & Alisi, 2009).

butyl hydroperoxide (Goya et al., 2007).

(Ruano et al., 2007).

**2.2 Anticancer activity** 

Hillestrom, 2006; Manna, 2005).

Hydroxytyrosol may have critical effects on the formation and maintenance of bone, and could be used as an effective remedy in the treatment of osteoporosis symptoms, as it can stimulate the deposition of calcium and inhibit the formation of multinucleated osteoclasts in a dose-dependent manner. HT also suppressed the bone loss of spongy bone in femurs of ovariectomized mice (Hagiwara et al., 2011).
