Docosahexaenoic acid, oxidation products

Total sterol or cholesterol Monoglyceride and diglyceride Phosphatidylcholine Docosahexaenoic acid (DHA) CO-1 fatty acids oxidation products oxidation products Z, conjugugated double bonds... 

Similar studies of lipid peroxidation products have been performed for other substrate lipids. Of particular interest are oxidation produets of docosahexaenoic acid (DHA), which have been termed F4-neuroprostanes (F4-NeuroPs) (Roberts et al, 1998). In contrast to AA, which is evenly distributed in all eell types in all tissues, DHA is highly eoneentrated in neuronal membranes (Salem et al, 1986 Montine et al, 2004). Thus, determination of F4-NeuroPs permits the speeifle quantifleation of oxidative damage to neuronal membranes in vivo (Montine et al, 2004). In faet, to our knowledge, F4-NeuroPs are the only quantitative in vivo marker of oxidative damage that is selective for neurons. 

Reactive aldehydes generated from hpid peroxidation are involved in CVD (266). Another example lies with the role of oxidative stress in the pathophysiology of asthma (267). Lipid peroxidation, as determined by plasma iso-prostanes, is related to disease severity in mild asthma. Tumor cell lines are sensitive to PUFA and to associated oxidation products (268). This sensitivity depends on the antioxidant defense mechanism, as well as on culture conditions. Hydroperoxy docosahexaenoic acid is a major metabolite, responsible for the cytotoxicity of DHA. 

Khair-El-Din TA, Sicher SC, Vazquez MA, Lu CY. Inhibition of macrophage nitric-oxide production and la-expression by docosahexaenoic acid, a constituent of fetal and neonatal serum. Am J Reprod Immunol 1996 36 1-10. 

Fig. 2. Interplay among superoxide anion, nitric oxide, and eicosanoids in high oxidative stress. The biological function of nitric oxide in target cells is influenced by the cellular redox state. In increased oxidative stress, which results in an oxidizing environment, NO readily form free radicals, including the highly reactive peroxynitrite (OONO ). Peroxynitrite can influence eicosanoid synthesis by interfering with different enzyme systems of the arachidonic acid cascade. Increased free radicals may also catalyze nonenzymic peroxidation of membrane PUFA (e.g., arachidonic acid), resulting in increased production of isoprostanes that possess potent vasoconstrictor activity. PLA, phospholipase NO, nitric oxide NOS, nitric oxide synthase NADPH oxidase, vascular NAD(P)H oxidase 02 , superoxide anion PUFA, polyunsaturated fatty acids EPA, eicosapentaenoic acid DHA, docosahexaenoic acid COX, cyclooxygenase PGI2 synthase, prostacyclin synthase.

Because the 12,15-diene has a 1,4-diene system, it oxidizes like linoleate to form two conjugated dienoic 12- and 16-hydroperoxides. However, in contrast to linoleate, the external 16-hydroperoxide is formed at a higher concentration than the internal 12-hydroperoxide, (with normalized concentrations of 58% and 42%) (Figure 2.12). Therefore, both the 9,15- and 12,15-dienes produce allylic radicals in which the terminal carbons 16 and 17, closest to the end of the fatty acid chain, are the most reactive with oxygen. The same preference of oxygen attack at the terminal double bond position is also observed in other polyunsaturated fatty acids with n-3 double bonds (linolenate, eicosapentaenoic and docosahexaenoic acids), and n-6 double bonds (arachidonic acid). Volatile decomposition products derived from hydroperoxides containing an n-3 double bond are particularly significant for their impact on flavor (Chapter 4). 

Production of TAG enriched with polyunsaturated fatty acids (PUFA) via lipase catalysis in codliver oil has also been described (Haraldsson et ah, 1989). Preparation of y-linolenic acid enriched TAG via rapeseed lipases (Syed Rahmatullah et aL, 1994 Jachmanian and Mukerjee, 1996) and microbial lipases (Akoh et aL, 1995, 1996) has also been reported. Incorporation of eicosapentaenoic and docosahexaenoic acids into peanut oil via transesterification catalysed by microbial lipases has been reported by Sridhar and Lakshminarayana (1992). According to Wada and Koizumi (1986) and Kimoto et aL (1994) interesterification of fish oils to form TAG containing PUFA in the 2-position rather than the 1,3-positions increases the oxidative stability of the modified oil as compared to its original counterpart. 

Polyunsaturated fatty acids, such as linoleic acid, a-linolenic acid, arachidonic acid and docosahexaenoic acid have characteristic physiological activities and are essential for human health. However, when these polyunsaturated fatty acids are exposed to oxygen, they are oxidized to form conqjlex oxidation products. Since autoxidation of unsaturated fatty acids decreases their biological availability in foods and produces offensive odors and... 

Radiation Biochemistry of Lipids. The rancidity that develops in stored fish is the result of oxidative reactions. Work being done with methyl docosahexaenoate shows that irradiation per se does not cause observable or measurable changes in this long-chain fatty acid ester. However, changes involving fatty acids go on at a higher rate in irradiated fishery products than in the nonirradiated counterparts (16). 

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