Chapter 16 - Antioxidant pharmacology

Abstract

Natural and synthetic antioxidants are used widely in modern medicine. Some have proven to be efficient geroprotectors—i.e., they have extended the life spans of laboratory animals, fishes, flies, and others when regularly added to food or drinking water. By definition, antioxidants are chemical scavengers of active free radicals and, thereby, the inhibitors of free-radical reactions of oxidation of fatty acids, edible fats, etc. However, neither natural antioxidants like vitamin E and flavonoids nor synthetic antioxidants can serve as efficient scavengers of oxygen free radicals in vivo, since the rate-constants of the antioxidants in the reactions with oxygen free radicals are negligibly small compared with natural antioxidant enzymes. In vivo, antioxidants work not so much to directly inhibit free radical processes but rather to prevent the formation of oxygen radicals and free radical oxidation processes in cells and tissues. In terms of system reliability theory, antioxidants provide prophylactic maintenance against reactive oxygen species. The particular preventive protection mechanisms are different for antioxidants of different types. For example, the synthetic antioxidant butylated hydroxytoluene prevents the generation of oxygen radicals as by-products of mitochondrial electron transport. At the same time, resveratrol and other flavonoids exert preventive antioxidant action by inducing the expression of antioxidant enzymes. Furthermore, antioxidants modulate an organism’s microbiota, while microbiotic metabolites promote beneficial effects on brain cells via gut–brain neural circuits. Thus, elucidating the true mechanisms of antioxidant therapy is now the task of systems biology.