RESUMO
Free radicals are continuously generated in almost all aerobic cells. If they are not scavenged by the integrated comprehensive array of endogenous antioxidant mechanisms, tissue damage occurs. It has been widely accepted that free radicals are implicated in a large number of medical disorders including cancer, inflammation, atherosclerosis, coronary heart disease and diabetes. Low levels of one or more of the essential antioxidants have been shown to be associated with many of these disorders. Thus, in such cases, the administration of exogenous antioxidants seems to be salutary. Nowadays, a great deal of effort being expended to find effective antioxidants for the treatment or prevention of free radical-mediated deleterious effects. The effectiveness of currently used exogenous antioxidant therapy stems most probably from the augmentation of the endogenous free radical scavengers such as enzymes [superoxide dismutase and selenium-dependent glutathione peroxidase] and vitamins [alpha-tocopherol, ascorbic acid and beta-carotene]. Many drugs have been also found to possess free radical scavenging activity. Among these are probucol, gliclazide, allopurinol and some calcium channel blockers. The free radical scavenging property exerted by drugs might account, at least in part, for some of their beneficial pharmacological actions