ABSTRACT
On earth, most life exists in a toxic atmosphere of oxygen. Lipid peroxidation is caused by an initiator, an environmental component that induces formation of an organic free radical (R·), or one of the reactive species of oxygen which may react with an organic molecule, also initiating an organic free radical. The environmental initiators of lipid peroxidation in vitro include the presence of oxygen and trace metals, the absence of antioxidants, and moderate to high temperatures. The products of lipid peroxidation are ethane, pentane, malondialdehyde, and lipofusion pigments. Following initiation of lipid peroxidation, the formation of an organic peroxy free radical (ROO·) and an organic hydroperoxide (ROOH) can rapidly lead to a variety of new species of free radicals (R·, RO·, and ·OH) which in chain reactions result in the oxidation of still other molecules. The small dietary food additives and cellularly synthesized antioxidants are shown to block initiation and break closed-loop free-radical-chain reactions.
