4] Suppression of hydroxyl radical reactions in biological systems: Considerations based on competition kinetics

Abstract

This chapter provides information to the suppression of hydroxyl radical (•OH) reactions in biological systems. Hydroxyl-radical-induced reactions form an essential part of many of the degradative processes that afflict life. In aqueous and oxygenated media, •OH radicals arise in various ways. These include Fenton-type processes involving biogenic H2O2, which is a product of the dismutation of superoxide; the latter is a product mainly of side reactions incidental to respiration and enzymatic oxidation processes, of the decomposition of certain peroxyl radicals, or of inflammatory processes in tissues. Hydroxyl radicals are also produced by ionizing radiation. Chemical damage to cell constituents that carry out critical functions, such as DNA, may have serious biological consequences. It is therefore natural to reflect on the way such deleterious processes might be mitigated by the intervention of drugs. Thus the involvement of free radicals in biological systems has become an important issue in medicine, and concepts based on the knowledge of the underlying free radical reactions are developed for the treatment of certain diseases with some measure of success.