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Another method of termination is the reaction between a lipid radical and a lipid peroxide, or the combination of two lipid peroxide molecules, resulting in stable nonreactive molecules. [ 4 ] [ 5 ] Reinforced lipids that become part of the membrane if consumed with heavy isotope diet also inhibit peroxidation.
Lipid peroxidation, or lipid oxidation, is a complex chemical process that leads to oxidative degradation of lipids, [1] resulting in the formation of peroxide and hydroperoxide derivatives. [2] It occurs when free radicals , specifically reactive oxygen species (ROS), interact with lipids within cell membranes , typically polyunsaturated fatty ...
Thiobarbituric acid reactive substances (TBARS) are formed as a byproduct of lipid peroxidation (i.e. as degradation products of fats) which can be detected by the TBARS assay using thiobarbituric acid as a reagent. TBARS can be upregulated, for example, by heart attack [1] or by certain kinds of stroke. [2]
This probably is an indication of the greater vulnerability of polyunsaturated fats to lipid peroxidation, against which vitamin E has been shown to be protective. [5] Examples of unsaturated fatty acids are palmitoleic acid, oleic acid, myristoleic acid, linoleic acid, and arachidonic acid.
Phosphatidylethanolamines in food break down to form phosphatidylethanolamine-linked Amadori products as a part of the Maillard reaction. [13] These products accelerate membrane lipid peroxidation, causing oxidative stress to cells that come in contact with them. [14] Oxidative stress is known to cause food deterioration and several diseases.
The antioxidant enzyme glutathione peroxidase 4 (GPX4) belongs to the family of glutathione peroxidases, which consists of 8 known mammalian isoenzymes (GPX1–8).GPX4 catalyzes the reduction of hydrogen peroxide, organic hydroperoxides, and lipid peroxides at the expense of reduced glutathione and functions in the protection of cells against oxidative stress.
Autoxidation is therefore a fairly broad term and can encompass examples of photooxygenation and catalytic oxidation. The common mechanism is a free radical chain reaction , where the addition of oxygen gives rise to hydroperoxides and their associated peroxy radicals (ROO•). [ 5 ]
The double bonds of an unsaturated fatty acid can be cleaved by free-radical reactions involving molecular oxygen. This reaction causes the release of malodorous and highly volatile aldehydes and ketones. Because of the nature of free-radical reactions, the reaction is catalyzed by sunlight. [7] Oxidation primarily occurs with unsaturated fats.