Free radical formation reducing substances

Figure 18. Formation of free radical and reducing substances in the reaction of glucose with X-butylamine (each 1 Mj in ethanol. Key +, free radical , reducing substances (determined by polarography) A, reducing ability (determined with...

Formation of Reducing Substances and Its Relation to Free Radical Formation (5)... 

Antioxidants are substances that are able to reduce the free radical concentrations in cells and the body. They also react at different stages of the free radical formation. They can be preventive, such as superoxide dismutase, or interceptive, such as vitamin C. Furthermore, the antioxidant defense systems of the human body can be classified into two groups, the enzymatic and non-enzymatic defense system. Most of the antioxidants present in the cell, such as superoxide dismutase, glutathione peroxidase, catalase, glutathione reductase and thioredoxin, are endogenous enzymatic systems and are produced within the cell [4]. Superoxide dismutase is an important endogenous antioxidant, and the first line of defense against free radicals. It converts superoxide radicals... 

Antioxidants are used to reduce or inhibit the oxidatimi of active substances or excipients. Active substances in parenterals which may undergo oxidative degradation are e.g. phenothiazines, catecholamines, polyene antifungal agents, steroids, morphine. Antioxidants either prevent the formation of free radicals (i.e. butylated hydroxyanisole. 

Another in vitro experiment investigated if Upofuscin formation in RPE cells was reduced by antioxidants. It was shown that a-tocopherol and the macular carotenoids, L and Z, have cham-breaking properties in peroxidation reactions of lipid membranes and also play a part in the quenching of free radicals. It was reported that formation of Upofuscin was significantly reduced as a result of the antioxidant substances in the RPE [100]. 

An isozyme of peroxidase has been found in the actively growing and differentiating parts of plants and animals which catalyzes the formation of the free radical of AA, which is a much more powerful electron donor than L-AA and can reduce an inert substance like 0-dinitrobenzene to dinitropheny1 hydroxylamine. AA alone is quite ineffective in this reaction (Gurevich, 1963). 

The inhibitors of oxidation reaction of fats are substances which reduce the oxidation rate, regardless of the mechanism of their action. These compounds include antioxidants, synergists, chelating agents and compounds decomposing hydroperoxides by nonradical reactions. Also agents stabiHsing hydroperoxides may reduce the reaction rate because they inhibit the formation of free radicals. 

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