Oleuropein is a phenolic compound derived from the leaves and oil of the olive tree Olea europaea as well as the leaves of the privet shrub. In the ancient world, olive oil was viewed as an essential substance and has been used for centuries in a wide variety of cutaneous treatments. Ancient Greeks bathed with olive oil (Phytother. Res. 2003;17:987-1,000), and ancient Egyptians and Romans used it in food, cosmetics, massage preparations for athletes, anointing substances, and salves for wounds.

Dietary Role of Olive Oil

The Mediterranean diet, reputed to be among the world's healthiest, features olive oil. Epidemiologic evidence now suggests that the Mediterranean diet, which also includes fruits, vegetables, and fish, is associated with reduced cancer and coronary heart disease risk. In addition, recent studies suggest that the olive oil-rich Mediterranean diet contributes to healthier aging and greater longevity (Eur. J. Clin. Invest. 2005;35:421-4).

The benefits of the Mediterranean diet have been partly attributed to the protective activity of the phenolic constituents caffeic acid and oleuropein present in extra-virgin olive oil (Med. Clin. (Barc) 2003;120:128-31). Oleuropein and hydroxytyrosol (a phenolic component of olive oil and a metabolite of oleuropein) have been found in vivo and in vitro to be potent antioxidants that confer significant biologic benefits, including cardioprotective effects (Med. Res. Rev. 2002;22:65-75; Curr. Atheroscler. Rep. 2001;3:64-7; Crit. Rev. Food Sci. Nutr. 2002;42:209-21).Visioli et al. have also shown that both compounds are strong scavengers of superoxide radicals and inhibitors of neutrophil respiratory burst (Biochem. Biophys. Res. Commun. 1998;247:60-4).

Benefits of Phenolic Compounds

Olive oils' phenolic compounds have demonstrated antimicrobial activity against several bacterial strains associated with intestinal and respiratory infections (Altern. Med. Rev. 2007;12:331-42; J. Nutr. Biochem. 2002;13:636-44). Bioavailable in humans, these compounds have also shown the ability to improve endothelial function as well as to modify hemostasis, exhibiting antithrombotic properties (Eur. J. Clin. Invest. 2005;35:421-4). Oleuropein is known to display numerous biologic properties, many of which have been ascribed to its antioxidant activities (Int. J. Cosmet. Sci. 2008;30:113-20). In addition to antioxidant and antibacterial properties, oleuropein is thought to possess antiviral and antifungal qualities.

The polyphenols oleuropein, tyrosol, hydroxytyrosol, and caffeic acid are the primary components of the polar fraction of virgin olive oil (Z. Naturforsch [C] 2000;55:814-9). A decade ago, de la Puerta et al. set out to ascertain the antieicosanoid and antioxidant effects in leukocytes of these olive oil constituents.

All four suppressed leukotriene B4 generation at the 5-lipoxygenase level in intact rat peritoneal leukocytes stimulated with calcium ionophore. None of the compounds was toxic to leukocytes at tested concentrations, and none significantly inhibited thromboxane generation through the cyclooxygenase pathway. The investigators concluded that oleuropein and the other phenolics present in virgin olive oil exhibit various antioxidant, lipoxygenase-inhibitory, and prostaglandin activities (Biochem. Pharmacol. 1999;57:445-9).

Slightly less than a decade ago, researchers showed that all three different classes of phenolic constituents in olive oil, including simple phenols (hydroxytyrosol, tyrosol), secoiridoids (oleuropein, the aglycone of ligstroside, and their respective decarboxylated dialdehyde derivatives), and lignans [(+)-1-acetoxypinoresinol and pinoresinol], exhibit potent antioxidant activity. They stressed that consuming extra-virgin olive oil, which is laden with these phenolic antioxidants in addition to squalene and oleic acid, should hinder oxidative stress and thus yield significant protection against various cancers (such as colon, breast, and skin), coronary heart disease, and aging (Lancet Oncol. 2000;1:107-12).