Introduction
Free radicals are reactive molecules with one or more unpaired electron(s). Living organisms are constantly exposed to them as a consequence of aerobic life and physiology. In normal situations, the endogenous anti-oxidant network that comprises several primary and secondary anti-oxidant mechanisms provides sufficient protection against reactive species like ROS and RNS (Sen, 1995). However upon different situations an imbalance between oxidative load and anti-oxidation might appear leading to increased oxidative stress. Elevated levels of oxidative stress are related to various phenomena including ageing (Trougakos et al., 2003).