ABSTRACT
The protective mechanisms against oxidative stress can be divided into two major categories: endogenously produced enzymatic antioxidants that include superoxide dismutase, glutathione peroxidase, catalase, glutaredoxin and thioredoxin. Non-enzymatic antioxidants include nutritionally derived vitamins and provitamins, flavonoids and polyphenols, proteins such as thiols and various other low-molecular-weight compounds as ubiquinone, uric acid (UA) and many more. Bilirubin and UA represent important endogenous antioxidants mainly found in the plasma. The heterogenic role of reactive oxygen species in living organisms and the beneficial but also deleterious effects of antioxidant supplementation show the complexity of the network and the dependency of various conditions. Muscle antioxidant defence systems are upregulated in response to exercise. The most common antioxidants used were vitamin E and vitamin C and various antioxidant combinations, also including the latter vitamins. The various ways of acting and the interaction with exogenic substances show the dependency of the Glutathione activity on the consumption of substances acting as antioxidants.
