Reactive oxygen species (ROS) possess a strong oxidizing
effect and induce damage to biological molecules, including
proteins, lipids and DNA, with concomitant changes
in their structure and function (Seifried et al. 2007). In a
series of pathological conditions, an extensive generation
of ROS appears to overwhelm natural defense mechanisms,
dramatically reducing the levels of endogenous antioxidants,
a condition named "oxidative stress" (McCord
2000); as epidemiological studies indicate that the major
nutritional antioxidants, vitamin E, vitamin C and β-carotene,
may be beneficial to prevent several chronic disorders
(Diplock et al. 1998), considerable interest has arisen in the
possible reinforcement of antioxidant defenses, both for
chemoprevention and treatment purposes (Maxwell 1997).
Two basic conditions must be fulfilled for an antioxidant;
(i) the compound should be present in low concentrations
relative to the substrate to be oxidized; and (ii) the species
resulting from its oxidation must be stable through intramolecular
hydrogen bonding stabilization