RESUMO
Oxidative stress is produced by the reactive oxygen/nitrogen species (ROS/RNS) which involves mitochondrial dysfunction. Mitochondria is one of the main sources of oxidative stress, as it utilizes the oxygen for the energy production. Overproduction of ROS, results in oxidative stress, which injures the cell structures, lipids, proteins, and DNA. Various oxidative events implicated in many diseases is due to oxidative stress which include alteration in mitochondrial proteins, mitochondrial lipids and mitochondrial DNA, which in turn leads to damage nerve cells as they are metabolically very active. Reactive oxygen/nitrogen species at moderate concentrations also play roles in normal physiology of many processes like signalling pathways, induction of mitogenic response and in defence against infectious pathogens. Oxidative stress has been considered to be the main cause in the etiology of neurodegenerative diseases, which includes Parkinson's disease (PD) and Alzheimer's disease (AD). Recent research on the dysfunction and function of PD associated genes has provided new fundamental insights into biochemical pathways that are linked with the disease process This review includes source of free radical generation, mitochondrial dysfunction and the mechanism involved in neurodegenerative diseases which involves both PD as well as in AD. This makes the mitochondria, the main target of PD and AD research