Polyunsaturated fatty acids oxygen species

Nitric oxide and peroxynitrite contribute to oxidative damage 569 Production of eicosanoids from polyunsaturated fatty acids such as arachidonic acid may generate reactive oxygen species 570 Brain antioxidant defenses modify ischemia-reperfusion injury 570 Reactive oxygen species may modify both the excitotoxic and the apoptotic components of ischemic brain damage 570... 

Oxidation to CO of biodiesel results in the formation of hydroperoxides. The formation of a hydroperoxide follows a well-known peroxidation chain mechanism. Oxidative lipid modifications occur through lipid peroxidation mechanisms in which free radicals and reactive oxygen species abstract a methylene hydrogen atom from polyunsaturated fatty acids, producing a carbon-centered lipid radical. Spontaneous rearrangement of the 1,4-pentadiene yields a conjugated diene, which reacts with molecular oxygen to form a lipid peroxyl radical. 

Precautions should be taken to prevent oxidation during lipid analysis. Polyunsaturated fatty acids in lipid samples are easily attacked by active oxygen species (e.g., free radicals), exacerbated by the presence of strong light and metal ions. Therefore, it is arule of thumb while working with lipids that samples should be handled in a way that minimizes contact with air, light, and metals. To accomplish this, handle samples in glass vessels, use Teflon-lined or coated materials, and maintain the samples... 

Primary targets for attack by oxygen-derived free radical species are the polyunsaturated fatty-acid (PUFA) moieties of membrane phospholipids. Attack on low-density lipoprotein PUFA (LDL PUFA) must also be considered and is of primary importance in the consideration of the aetiology of atherosclerosis. The mechanism of all such peroxidation processes is likely to be the same and the inhibitory effect of antioxidants toward PUFA can be considered to be... 

Several mechanisms of antioxidant action have been proposed. The presence of antioxidants may result in the decreased formation of the reactive oxygen and nitrogen species in the first place. Antioxidants may also scavenge the reactive species or their precursors. Vitamin E is an example of this latter behavior in its inhibition of lipid oxidation by reaction with radical intermediates generated from polyunsaturated fatty acids. Some antioxidants can bind the metal ions needed to catalyze the formation of the reactive oxidants. Other antioxidants can repair oxidative damage to biomolecules or can influence enzymes that catalyze repair mechanisms. 

Polyunsaturated and oxygenated fatty acids, obtained from triacylglycerols (TAG) of several different plant and animal species, are valuable materials feedstock for value-added products in a variety of industries food, pharmaceutical, cosmetics, and paints and coatings. The acyl species, their chemical structure, and their most abundant sources are summarized in Table 1. In contrast to inexpensive Cie and Cig saturated and A9-unsaturated acyl groups, such as palmitic (16 0), stearic (18 0), oleic (18 l-9c), linoleic (18 2-9c, 12c), and a-linolenic acid (ALA 18 3-9c, 12c,15c), recovered from the oil of soybean and other common sources, and C4-C16 saturates from palm oil and milk fat, polyunsaturated and oxygenated acids are derived from less common sources, and particularly for polyunsaturated fatty acid (PUFA), are typically present at only 20 0% purity. 

Allyl)iron(III) complexes have been implicated in the enzymatic lipoxygenation of polyunsaturated fatty acids. In the proposed model, concerted allylic deprotonation and electrophilic addition see Electrophilic Reaction) of Fe gives an iron allyl species, which undergoes Fe-C bond insertion by O2. In model studies, reaction of allyltributyltin compounds with FeBrs, followed by exposure to oxygen, gives oxidation to the carbonyl compounds (26) through presumed intermediates (27). 

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