Free radicals derived from oxygen, and medicine

Toxic free radicals may be produced by many reactions, which are necessary for the maintenance of normal metabolism, and the production of energy in cells. The origin, reactivity with other molecules and removal of free radicals, is in the foreground of interest since their effect is mostly toxic and result in a whole series of pathological states of cells, organs and whole organisms. Production of these radicals increases in oxidative stress and in the presence of ions of metals (chiefly iron), leads to the creation of more reactive metabolites. The generally accepted view is that the main biological actor in damaged tissues is the hydroxyl radical (OH), which is created in the iron catalyzed Haber-Weiss reaction. The balance between the increased creation of free radicals in various pathological states, or unfavourable conditions in the environment, and natural antioxidants of a low-molecular (vitamin C, E, glutathione etc.) or enzyme character (superoxide dismutase, glutathione peroxidase, glutathione reductase, catalase, etc.), plays the chief role in damage which is the cause of many diseases and ageing. (Fig. 3, Tab. 5, Ref. 62.).