Some of the major ROS formed as a consequence of aerobic metabolism include superoxide anion (O2), hydrogen peroxide (H2O2), and the highly reactive hydroxyl radical (OH). In addition to increased metabolic demands, inflammatory events also may contribute to elevated ROS and the development of oxidative stress. Large volumes of O2 and H2O2 are produced during the respiratory burst activity of phagocytic cells by stimulation of NADPH oxidase for the destruction
of invading pathogens (