The imbalance between reactive oxygen species (ROS) production and antioxidant defenses determines the condition called oxidative stress. When there is an increase in ROS production or a decrease in the antioxidant defenses, this systemic antioxidant/pro-oxidant imbalance may lead to the accumulation of oxidative damage, which, in turn, may lead to a modification of biomolecules. These consist of reactions resulting in protein adducts, DNA oxidation, and formation of lipid peroxides, which, in turn, reduce the cellular functional capacity and increase the risk of disease development. The body has natural scavenging systems against free radicals and other reactive species. However, sometimes the endogenous antioxidant capacity is exceeded by the production of ROS. When this occurs, exogenous antioxidants exert important function for the human health. These bioactive compounds act preventing and neutralizing the formation of new reactive species and free radicals. In some cases, an increase of ROS can help the host to resolve an infection or even to control the tumor growth. Finally, the levels of ROS can be perceived by signal transduction pathways involving known targets (i.e., p53, Ras, and NF-κB) and regulate physiopathological events such as the cellular cycle, apoptosis, and inflammation.
Part of the book: Novel Prospects in Oxidative and Nitrosative Stress