Cancer Chemopreventive Activity of Hydroxytyrosol: A Natural Antioxidant from Olives and Olive Oil

Several aspects of the Mediterranean diet have been associated with a reduced risk not only of cardiovascular disease, but also of several cancers, and it has been suggested that up to 25% of colorectal, 15% of breast and 10% of prostate, pancreas, and endometrial cancers could be prevented by shifting to a Mediterranean lifestyle. Olive oil, a central component of the Mediterranean diet, is thought to play a key role in these benefits. The cancer chemopreventive activity of olive oil has been indicated in different studies. Bartoli et al. demonstrated that dietary olive oil prevented the development of aberrant crypt foci and colon carcinomas in rats. These effects were suggested to be partly mediated by the modulation of arachidonic acid metabolism and local PGE synthesis. A similar outcome was observed for dimethyl-benz(a)anthracene-induced mammary carcinogenesis in rats, where dietary olive oil supplementation reduced tumor incidence, multiplicity, and volume. Olive oil was shown to induce significant levels of apoptosis (HT29 and Caco-2) and cell differentiation (Caco-2) but did not inhibit proliferation of either cell line. The beneficial health effects of olive oil have been mainly attributed to the high content of monounsaturated fat, namely oleic acid. However, its composition includes not only fat but also other nutritional components that are not present in any other edible oils; these components include several hundreds of non-fatty micronutrients, such as squalene, phytosterols, tocopherols, and secoiridoids, among others. Consequently, the health-protecting effect of olive oil can be mediated by these minor compounds. Recently, the cancer chemopreventive activity on colon cancer of an extract from the skin of olive fruits composed of maslinic acid (73.25%) and oleanolic acid (25.75%) has been reported. © 2010