Fig. 1

a Cellular Sources of ROS. ROS can be generated intracellularly via the action of various organelles, enzymes, and processes. b Conversion of Superoxide to Secondary ROS. Once produced, superoxide can interact with various molecules to generate secondary radicals. Superoxide can react with nitric oxide to produce peroxynitrite. Superoxide dismutase can also convert superoxide into hydrogen peroxide, which can then undergo a Fenton reaction to produce hydroxyl radicals and ions. Interaction of superoxide with protons can produce hydroperoxyl radicals. These secondary radicals are highly reactive and can be neurotoxic via alterations of macromolecules and amplification of oxidative stress