Hydroxyl Radical and Its Scavengers in Health and Disease

Abstract

It is generally believed that diseases caused by oxidative stress should be treated with antioxidants. However, clinical trials with such antioxidants as ascorbic acid and vitamin E, failed to produce the expected beneficial results. On the other hand, important biomolecules can be modified by the introduction of oxygen atoms by means of non-oxidative hydroxyl radicals. In addition, hydroxyl radicals can reduce disulfide bonds in proteins, specifically fibrinogen, resulting in their unfolding and scrambled refolding into abnormal spatial configurations. Consequences of this reaction are observed in many diseases such as atherosclerosis, cancer and neurological disorders, and can be prevented by the action of non-reducing substances. Moreover, many therapeutic substances, traditionally classified as antioxidants, accept electrons and thus are effective oxidants. It is described in this paper that hydroxyl radicals can be generated by ferric ions without any oxidizing agent. In view of the well-known damaging effect of poorly chelated iron in the human body, numerous natural products containing iron binding agents can be essential in the maintenance of human health. However, beneficial effects of the great number of phytochemicals that are endowed with hydroxyl radical scavenging and/or iron chelating activities should not be considered as a proof for oxidative stress.

Oxidation Inhibits Iron-Induced Blood Coagulation

“…It is known that the transformation of fibrin monomers into fibrin occurs by means of ionic bonds. By contrast, hydroxyl radical‑induced modification of FBG irreversibly affects its physicochemical properties rendering them more hydrophobic than the native molecules [14]. Spontaneous aggregation of soluble hydrophobic protofibrils results in the formation of dense matted deposits, which when fused with red blood cells, contributes to the resistance of thrombi to the fibrinolytic degradation [15].…”

Cerium oxide nanoparticle: a remarkably versatile rare earth nanomaterial for biological applications

“…In vivo, excess H 2 O 2 is believed to have more toxic potential than superoxide because it is the substrate for the Fenton reaction and generates hydroxyl radicals (OH Á ), the most destructive reactive oxygen species (ROS). 49 Fortunately, CeONP has both catalase-and SOD-like activities. The H 2 O 2 generated in the SOD-mimetic process can enter into the catalase-mimetic dismutation cycle and produce innocuous H 2 O and O 2 .…”

“…The hydroxyl radical ( Á OH) 49 is one of the strongest oxidants and most biologically active free radicals. There are two methods by which living systems remove hydroxyl radicals: blocking hydroxyl radical initiation by antioxidant enzymes (SOD, glutathione peroxidase and catalase) or breaking the hydroxyl radical chain reaction using nonenzymatic antioxidants.…”

Reactivity of phenolic compounds towards free radicals under in vitro conditions

“…Hydroxyl radicals are the most destructive reactive oxygen species in food and biological systems. Due to their relatively short in vivo half-life, they can induce oxidative damage to almost all important biomolecules, including polyunsaturated fatty acids, nucleic acids, amino acids and proteins (Lipinski 2011).…”