A Study on the Action of Antioxidants and Development of Synergists

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There is now an increasing number of evidence which suggests the involvement of free radical mediated oxidations of lipids, proteins, enzymes, and nucleic acids in a variety of pathological events, cancer and aging. This study was carried out aiming at elucidating the rate and mechanism of the action of various chain-breaking antioxidants and also the synergistic inhibition of oxidation.The water-soluble antioxidants such as ascorbic acid (vitamin C), uric acid, cysteine, and glutathione acted as antioxidant by scavenging aqueous radicals before they attack the membranes.However, they can not scavenge lipophilic radicals within the lipid layer of membranes and low density lipoprotein. Tocopherols (vitamin E) acted as lipophilic antioxidant within the membranes.The rate and mechanism of scavenging of lipid peroxyl radicals were fint studied in homogeneous solution by measuring oxygen uptake, products formation, chemiluminescence, and free radicals with election spin resonance. The oxida … More tion of phospholipid liposomal membranes and its inhibition were studied aiming specifically at elucidating the action of antioxidants in the membranes. It was found that tocopherols suppress the oxidation of phosphatidylcholine liposomal membranes by scavenging both aqueous radicals attacking from outside of the membranes and lipophific radicals within the membranes. It was suggested that laterally tocopherols more fairly rapidly but that it gets less effluent for tocopherols to scavenge radicals as they go deeper into the interior of the membrane. The phytyl side chain had a profound effect in the retainment of tocopherols in the membranes but it makes tocopherols difficult to move between the membranes. On the other hand, 2,2,5,7,8-pentamethyl-6-chromanol could penetrate and transfer between the liposomal membranes freely. Tocophemls also suppressed the oxidative hemolysis induced by free radicals. It was found that tocopherol within the erythrocyte membranes was the most effective in suppressing hemolysis by scavenging chain-carrying radicals and breaking the chain propagation. The interaction between antioxidants and metal ion was also studied. The rate and mechanism of synergistic inhibition of oxidation by tocopherol and reducing agent such as ascorbic acid, cysteine and glutathione have been also studied. Less