Comparison of Antioxidant and Prooxidant Activity of Various Synthetic Antioxidants

In a classical sense, the term “antioxidant” denotes a low molecular weight compound capable of terminating the chain reaction of lipid peroxidation by scavenging lipid peroxy radicals. In biology and medicine, the term is now used in a broader sense, including e.g. enzymes which detoxify ROS* such as SOD, catalase or glutathione peroxidase, and agents which inhibit the formation of specific ROS such as iron chelators. Still, the classical antioxidants of which α-tocopherol is a prototype have a role in experimental re search on oxidative stress and probably in therapeutic regimens directed towards ROS-mediated diseases. Besides its chain-breaking action in lipid autoxidation, these low molecular weight antioxidants may also react with the inorganic oxygen radicals derived from partial reduction of molecular oxygen. The most extensively studied compound in this respect is a-tocopherol. Thus, it has been shown that chromanoxyl radical formation from α-tocopherol can be achieved by O2- and by OH·1–3. Less numerous data exist on the reaction of synthetic antioxidants with O 2 - and OH· in model systems4,5