Free Radical Inorganics

Free radicals, acknowledged in chemistry since the birth of the 20th century, were originally used to describe common compounds in organic and inorganic chemistry, and several chemical definitions for them were suggested. Only in 1954 when the pioneering work of Daniel Gilbert and Rebecca Gersham was published (Gilbert DL (ed.), 1981) were these radicals proposed as important players in biological environments and responsible for destructive processes in the cell. After which, in 1956, Herman Denham (Harman D, 1956) suggested that these species might play an important role in physiological events especially in the aging process (Harman D, 1981). His hypothesis, the free-radical theory of aging, inspired various studies and research efforts

As a candle burns out much faster in oxygen than in air, the body becomes quickly exhausted in this “pure kind of air.” The toxicity of the atmospheric oxygen molecule had already been used by our ancestors for therapeutic purposes, such as treatment of places infected with the anaerobic bacterium Clostridium by exposure to air (Halliwell B, Gutteridge JM, 1999). The valuable use of the toxic effect of oxygen has been applied in hyperbaric and irradiation therapy (von Sonntag C, 1987). The advancement of submarines, diving as a sport, and medicine has contributed much to the knowledge of oxygen, its derivatives, and its toxicity (Balentine JD, 1982). Cases of blindness in young infants born prematurely in the 1940s were associated with the high oxygen concentration in the newly invented incubators (Gitto E, Reiter RJ, Karbownik M, Xian-Tan D, Barbereri I, 2001). This pathology, called retinopathy of prematurity (ROP), was easily controlled by balancing the oxygen concentration in the incubators. Nowadays, we are again facing an increase in

In contrast, a substance that donates electrons is a reductant or reducing agent (Cao G, Prior RL, 1998). In general, a chemical reaction in which a substance gains electrons is defined as a reduction (SchaferFQ, BuettnerGR, 2001). Oxidation is a process in which a loss of electrons occurs. When a reductant donates its electrons, it causes another substance to be reduced, and, when an oxidant accepts electrons, it causes another substance to be oxidized (Hrbac J, Kohen R, 2000). In biology, a reducing agent acts via donation of electrons, usually by donation of hydrogen or removal of oxygen. An oxidation process is always accompanied by a reduction process in which there is usually a loss of oxygen, while in an oxidation process there is a gain in oxygen (Hrbac J, Kohen R, 2000). Such reactions, called redox reactions, are the base for numerous biochemical pathways and cellular chemistry, biosynthesis, and regulation (ShapiroM, 1972). They are also important for understanding biological oxidation and radical/antioxidant effects. While reductant and oxidant are chemical terms, in biological environments they should be termed antioxidant and pro-oxidant, respectively (Cao G, Prior RL,