The imbalance between reactive oxygen species (ROS) and antioxidant capacity of the organism leads to a condition of oxidative stress (Urso and Clarkson, 2003). Studies in humans and laboratory animals have reported that oxidative stress is related to some common degenerative diseases, such as cancer and cardiovascular pathologies (Pellegrini et al., 2003). Oxidative stress has also been identified as causative agent for diseases, such as decline of immune function and atherosclerosis (Meydani et al., 1998). In particular, reactive oxygen metabolites such as superoxide (O2-), hydrogen peroxide (H2O2) and hydroxyl radical (OH.) have been reported to act as cytotoxic agents and damage unsaturated lipids in membranes (Girotti, 1998)
