Olive oil hydroxy-isochromans

Natural antioxidants present in the diet increase the resistance toward damages due to oxidation and may have a substantial impact on human health. Dietary antioxidants include ascorbate, tocopherols, carotenoids, and bioactive plant phenols (Boskou, 2006). Widely distributed in the plant kingdom and abundant in our diet, today plant phenols are among the most talked about classes of phytochemicals (Boskou, 2006); the beneficial health effect of the Mediterranean diet has been partly ascribed to the presence of these compounds. In fact, the high content of vegetables, fruits, cereals, wine, and olive oil, typical of the Mediterranean diet, has been associated with a lower risk of coronary heart disease, neurodegenerative diseases, and cancer (Keys, 1995; Owen et al., 2000a; Visioli et al., 2000; Harwood and Yaqoob, 2002; Huxley and Neil, 2003; Visioli et al., 2004; Arts and Hollman, 2005). Several studies have shown that extra virgin olive oil contains an abundance of phenolic antioxidants including simple phenols (hydroxytyrosol, tyrosol), aldehydic secoiridoids, flavonoids, and lignans (acetoxypinoresinol, pinoresinol) (Owen et al., 2000b). The polar phenolic compounds present in olive oil are a very important class of minor constituents and they are related to the stability of the oil but also to its biological properties (Visioli et al., 2004; Boskou et al., 2005; Bendini et al., 2007). Olive oil, the main fat component of the Mediterranean diet, consists primarily of triacylglycerols rich in the monounsaturated fatty acid, oleic acid. The nonglyceride constituents of extra virgin olive oil, which comprise approximately 0.5–1.0%, include at least 30 phenolic compounds (Tuck and Hayball, 2002). These phenolic compounds are responsible for its typical taste and contribute to the resistance of the oil to oxidative rancidity (Boskou, 1996). The phenolic content of olive oil depends on a number of factors, including cultivar, degree of maturation, possible infestation by the olive fly Dacus olea, climate, and mainly production and storage of the oil (Brenes et al., 1999; Boskou, 2000; Manach et al., 2004). Phenols are compounds with an aromatic ring structure with one or more hydroxyl groups. Phenols with two or more hydroxyl groups show antioxidant capacity in vitro, whereas phenols with one hydroxyl group have little or none (Rice-Evans et al., 1996; Leenen et al., 2002). Extra virgin oil contains phenolic substances with either one or more hydroxyl groups. The types of phenols in extra virgin oil are different from those of the olive fruit. The olives mainly contain the polar glycosides oleuropein and ligstroside, which are the parent compounds of the less polar oleuropein and ligstroside aglycones. These aglycones and their derivatives are the most abundant phenols in olive oil.