Lipid-Soluble Antioxidants: Biochemistry and Clinical ApplicationsAugustine S. H. Ong, PACKER Antioxidants inhibit the formation and spread of free radicals which can be damaging in biological systems. Free radicals form in biological systems through metabolism, but it is also realized that exogenous environmental sources, such as radiation, food, and drugs, contribute significantly to the generation of free radicals in biological systems. Being reactive species, free radicals are short-lived and do not travel far from cellular targets. Their concentration in biological systems is very low and is difficult to detect directly by electron spin resonance spectroscopy (ESR). Indirect methods of reactions of radicals with specific biomolecules are also sufficiently sensitive to detect quantitatively their presence. Thus the response of antioxidant defenses which react with radical species, can serve as an indirect measure that free radicals have been formed. Redox-based antioxidants change their oxidation state and antioxidants become free radicals themselves. Often, however, the antioxidants give rise to more persistent free radicals, sometimes owing to delocalization of the lone electron around ring structures (in vitamin E, ubiquinones, and certain carotenes). Persistent free radicals react only rarely and the precursors often can be regenerated in biological systems. In recent years, it is becoming clearer from biochemical studies on how the major lipophilic antioxidants work. Particular attention has been given to vitamin E and quinones found in animal and plant membranes and in carotenoids, for the protection of membranes in lipoprotein systems. Flavonoids form another rich and varied source of natural antioxidants. |
Contents
The reactivity of tocotrienols and other lipidsoluble antioxidants towards | 17 |
Physicalchemical studies of vitamin E in membranes | 27 |
Synergistic effect of lipid hydroperoxyl radical scavenging and lipid | 47 |
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Lipid-Soluble Antioxidants: Biochemistry and Clinical Applications ONG,PACKER No preview available - 2012 |
Common terms and phrases
1992 Birkhäuser Verlag a-Toc a-tocopherol activity AFB₁ animals antioxidants Applications A.S.H. Ong artemisinin atherosclerosis B-carotene Basel/Switzerland Biochem Biochemistry and Clinical Biol biological Biophys blood cancer carcinogens carotene carotenoids catalase Chem cholesterol Clin Clinical Applications A.S.H. concentration cytotoxic damage decreased deficiency diet dietary disease effect enzyme erythrocytes ethanol fatty acids flavonoids free radicals glutathione heart human hypercholesterolaemia increased incubation induced infection inhibition inhibitors intake isoproterenol levels lipid peroxidation Lipid-Soluble Antioxidants lipoprotein liver lung macrophages malaria membrane metabolism mice microsomal mitochondrial mutagenicity normal Nutr nutritional observed oxygen Packer eds palm oil parasite patients plasma platelet platelet aggregation protection protein PUFAs quercetin reaction reactive receptor red cells reduced reoxygenation reperfusion retinol role scavenging serum sesaminol shown studies supplementation Table tissue Toc3 tocotrienols Toskulkao triglycerides tumor cells tumoricidal action vitamin vitamin E vitro vivo µg/ml