Generation of reactive oxygen species is a physiological process that take place in every aerobic organism. Oxidative stress is defined as a disturbance in the balance between the production of free radicals and antioxidants in favor of the oxidants. The imbalance between those two fractions may potentially lead to cell damage at molecular level. Since oxidants are formed at a different rate as a normal product of aerobic metabolism, complex biochemical mechanisms are required to regulate the entire process.