Peroxidizing lipids

Flavonoids are chain-breaking antioxidants in lipid-like solvents like chlorobenzene, although the k(inh) is smaller than for a-tocopherol and the lag-phase accordingly less evident. For peroxidating lipids in chlorobenzene the clear lag-phase for a-tocopherol became longer when quercetin or catechin were present. The effect appears to be additive and a regeneration of a-tocopherol by quercetin or catechin in this lipid-like solvent should rather be termed a co-antioxidative effect (Pedrielli and Skibsted, 2002). 

Lipid peroxides Lipid peroxy radicals Lipid alkoxyl radicals Aldehydes... 

A vesicnlation defensive mechanism is in operation to remove peroxidized lipids from the thylakoid membranes . 

Yonei, S. Furui, H. (1981) Lethal and mutagenic effects of malondialdehyde, a decomposition product of peroxidized lipids, on Escherichia coli with different DNA-repair capacities. Mutat. Res., 88, 23-32... 

Baumgartner, W.A., Baker, N., Hill, V.A., and Wright, E.T. 1975. Novel interference in thiobar-bituric acid assay for lipid peroxidation. Lipids 10 309-311. 

It is evident that all the described methods are based on reduction reactions. Substrates react either with long-living radicals (TEAC, TRAP), AOC (ORAC) or with the iron complex compound (FRAP), AOM concentration are obtained as a result of enzymatic reactions [51] or their existing level is registered with electron-spin resonance [52], Various modifications of peroxidation lipid reaction can also be applied [53],... 

Fig. 7.3 Reactions showing the generation of ROS during lipid peroxidation and oxidative stress. Hydroxyl radical ( OH) lipid radical ( lipid), peroxyl radical (lipid-OO ) lipid peroxide (lipid-OOH) nitric oxide ( NO) nitrogen dioxide (N02) peroxynitrite anion (ONOO-) hypochlorous acid (HOC1), and hydrogen peroxide (H202)...

Asakawa, T. and Matsushita, S. (1979) Thiobarbituric acid test for detecting lipid peroxides, Lipids 14, 401-406. 

G9. Glavind, J., Hartmann, S., Clemmensen, J., lessen, K. E., and Dam, H., Studies on the role of lipoperoxides in human pathology. The presence of peroxidized lipids in atherosclerotic aorta Acta Pathol. Microbiol. Scand. 30, 1-6 (1952). 

Lipid peroxidation Lipid peroxidation Generates 02 [anticarcinogenic, apoptotic, chemopreventative]... 

Iron being a redox-active metal, it most hkely exerts its toxic effects through the generation of hydroxyl radical or by generation of ferryl ion. In iron loaded condition, there is generation of radical species leading to hpid peroxidation. Lipid peroxidation of cellular membrane would have deleterious effects on their function and hence on the function of the cell. There is also irreversible oxidation of ascorbic acid. Deficiency of ascorbic acid can lead to a reduction in the amount of iron available for erythropoiesis. 

Nitric oxide released by macrophages during inflammation reacts with active oxygen to form peroxynitrite. Peroxynitrite nitrates protein and peroxidizes lipids. y-Tocopherol (the principal form of vitamin E in the United States diet) and a-tocopherol (the major form present in the European diet and in supplements), both protect against peroxynitrite-induced lipid oxidation. [13]. Christen et al. reported that lipid hydroperoxide formation in liposomes is inhibited more effectively by y-tocopherol than a-tocopherol by a non-antioxidant mechanism [14]. However, Goss et al. [15] concluded that the presence of a-tocopherol attenuates nitration of both y-tocopherol and tyrosine, showing that nitration of... 

Chio, K. S., and Tappel, A. L. (1969). Inactivation of ribonudease and other cnTymes by peroxidizing lipids and by malonaldehyde. Biodtemistry 8,2827-7832,... 

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