Author: Tse, Lai-wa Denise
Title: The effect of quercetin and vitamin E on iron induced and hydrogen peroxide induced lipid peroxidation of rat brain mitochondria membrane
Degree: M.Sc.
Year: 1998
Subject: Membrane lipids -- Peroxidation
Active oxygen
Free radicals (Chemistry) -- Pathophysiology
Vitamin E
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Department of Applied Biology and Chemical Technology
Pages: ix, 96 leaves : ill. ; 30 cm
Language: English
Abstract: Lipid peroxidation is one of the most extensively studied manifestations of oxygen activation in biology. It involves the formation and propagation of lipid radicals, the uptake of oxygen, a rearrangement of the double bonds in unsaturated lipids, and the eventual destruction of membrane lipids. It is widely recognized that transition metals such as iron, copper or zinc are involved in both the initiation and the reinitiation phase of the process of membrane lipid peroxidation. H2O2 is not a free radical as it has no unpaired electrons, but it makes OH﹞ ready if one extra election is added to it. Therefore, H2O2 is a mobile time bomb as it is poorly reactive itself but can make extremely reactive OH﹞ ready at any time if an electron is supplied to it. The production of free radicals and the chain reaction initiated by them lead to disintegration of the cells and the cellular organelles. Lipid peroxides and related free radicals occurring excessively in the human body, is a direct cause of many diseases, especially age-related diseases such atherosclerosis, cataract, brain diseases such as Parkinson's disease and even aging itself. In this experiment, the effect of two antioxidants: vitamin E and quercetin on iron and hydrogen peroxide induced lipid peroxidation of rat brain mitochondria membrane was investigated. Rat brain mitochondria membrane was extracted from fresh brain tissue by homogenizing the cells and by differential centrifugation. The extracted membrane was then incubated with appropriate concentration of iron salt and hydrogen peroxide. The amount of lipid peroxide formed in lipid peroxidation reaction indicated the extent of the membrane lipid peroxidation. Lipid peroxide in the sample was heated in acid medium to convert to malondialdehyde (MDA), which would react with thiobarbituric acid to form pink pigment. It was measurable by fluoremetric method. The level of lipid peroxidation was expressed in term of MDA. The result of the experiment showed that both quercetin and vitamin E possess inhibitory effect on iron and hydrogen peroxide induced lipid peroxidation in rat brain mitochondria membrane. In the experiment, vitamin E was more effective than quercetin in inhibiting membrane lipid peroxidation induced by iron, however, the inhibitory effect of vitamin E and quercetin on hydrogen peroxide induced membrane lipid peroxidation was comparable. As the brain membrane was very sensitive to iron oxidation, the level of lipid peroxidation induced by iron was a little exaggerated under this experimental condition. For a better revelation of the effect of the two antioxidants on iron induced lipid peroxidation, it was suggested a submicromolar concentration of iron should be employed.
Rights: All rights reserved
Access: restricted access

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