Superoxide dismutase mimics, other mimics, antioxidants, prooxidants, and related matters

A significant number of low molecular weight metal complexes as well as metal-free compounds that are capable of scavenging superoxide and/or other radicals and reactive species in simple systems have been proposed to be used as potential drugs in the case of various diseases and/or as antiaging agents. Some have been used or suggested to be used as diagnostic tools for the involvement of such species in biological processes. In the present work, analysis of such claims indicates that their use as specific detectors of superoxide or of other reactive oxygen species is unsupported and might be confusing. Many of these compounds exert beneficial effects by counteracting the toxic effects of oxidative stress in a significant number of models of pathological processes. However, it is concluded that these actions are more likely due to other effects including prooxidant actions and that their beneficial effects also may be exerted in pathological processes that do not practically involve reactive oxygen species. Adaptation may be a common mode of action explaining a sizable portion of the beneficial effect of the so-called mimics and other compounds including prooxidants.