Unsaturated fatty acid oxidation

Chemical bleaching is never used on oils intended for edible use because it oxidizes unsaturated fatty acids to cause off-flavors. However, it does find wide usage for specialty linseed oil, for the paint industry, and fatty chemicals such as sorbitan esters of fatty acids and sodium stearoyl lactylate. Residual peroxide is destroyed by heating above its decomposition temperature. 

Ecostar (St. Lawrence Starch Company). This product associates PE with a mixture of starch and auto-oxidant unsaturated fatty acids. The global content of starch is between 6 and 15%. The degradation process then follows two mechanisms in the first, the starch is fragmented, then assimilated by microorganisms, whereas in the second, the interaction between the auto-oxidants and the metallic complexes from soil or water gives peroxides that attack the synthetic polymer chains. 

Together with 2,4-dienoyl-CoA reductase, enoyl-CoA isomerase allows cells to oxidize unsaturated fatty acids containing cis double bonds via oxidation. 

Two mechanisms for the toxicity of 6-OHDA have been proposed. First, auto-oxidation could generate ROS and subsequently oxidize unsaturated fatty acids of lipids or thiol groups of proteins. Second, 6-OHDA uncouples mitochondrial oxidative phosphorylation (Wagner and Trendelenburg, 1971). Whether the neurotoxicity of 6-OHDA can be attributed to the production of ROS or dihydroxyindoles (for a review, see Thoe-nen and Tranzer, 1973) is not yet defined. Degeneration of nigrostriatal neurons after intracerebral injections of 6-OHDA to rats is potentiated by administration of iron (Ben-Shachar and Youdim,... 

The superoxide radical anion reacts at an exceptionally high rate (k = 1.9 x 10 lmol s ) with nitrogen oxide (NO), the monomer being present as the free radical, to give peroxy nitrite (ONOO ). NO is formed in animal and plant foods from arginine by nitrogen oxide synthase (cf. 9.8.1). It is relatively stable with a half life of 400 s (H2O). Peroxy nitrite is a versatile oxidant it oxidizes unsaturated fatty acids, ascorbic acid, tocopherols, uric acid and amino acids, among... 

Monooxygenase is another enzyme that requires an NADP(H) cofactor to oxidize unsaturated fatty acid bonds to a hydroxyl group. Immobilization of the flavin-containing monooxygenase-3 has not been studied for BFC applications, but it has been used in a trimethylamine biosensor [103]. 

POP is active in inducing hemolysis in erythrocytes, in oxidizing unsaturated fatty acids and altering cell membrane Hpids. POP is generally stable at room temperature and in organic solvents, while heat and water decompose them, as do ferrous ions.""... 

He/minthosporium (15). The mode of action is considered to be inhibition of the enzyme NADPH-cytochrome C reductase, which results in the generation of free radicals and/or peroxide derivatives of flavin which oxidize adjacent unsaturated fatty acids to dismpt membrane integrity (16) (see Enzyme inhibitors). 

Interest in synthetic naphthenic acid has grown as the supply of natural product has fluctuated. Oxidation of naphthene-based hydrocarbons has been studied extensively (35—37), but no commercially viable processes are known. Extensive purification schemes must be employed to maximize naphthene content in the feedstock and remove hydroxy acids and nonacidic by-products from the oxidation product. Free-radical addition of carboxylic acids to olefins (38,39) and addition of unsaturated fatty acids to cycloparaffins (40) have also been studied but have not been commercialized. 

Cobalt in Driers for Paints, Inks, and Varnishes. The cobalt soaps, eg, the oleate, naphthenate, resinate, Hnoleate, ethyUiexanoate, synthetic tertiary neodecanoate, and tall oils, are used to accelerate the natural drying process of unsaturated oils such as linseed oil and soybean oil. These oils are esters of unsaturated fatty acids and contain acids such as oleic, linoleic, and eleostearic. On exposure to air for several days a film of the acids convert from Hquid to soHd form by oxidative polymeri2ation. The incorporation of oil-soluble cobalt salts effects this drying process in hours instead of days. Soaps of manganese, lead, cerium, and vanadium are also used as driers, but none are as effective as cobalt (see Drying). 

The dimer acids [61788-89-4] 9- and 10-carboxystearic acids, and C-21 dicarboxylic acids are products resulting from three different reactions of C-18 unsaturated fatty acids. These reactions are, respectively, self-condensation, reaction with carbon monoxide followed by oxidation of the resulting 9- or 10-formylstearic acid (or, alternatively, by hydrocarboxylation of the unsaturated fatty acid), and Diels-Alder reaction with acryUc acid. The starting materials for these reactions have been almost exclusively tall oil fatty acids or, to a lesser degree, oleic acid, although other unsaturated fatty acid feedstocks can be used (see Carboxylic acids. Fatty acids from tall oil Tall oil). 

The Goodyear vulcanization process takes hours or even days to be produced. Accelerators can be added to reduce the vulcanization time. Accelerators are derived from aniline and other amines, and the most efficient are the mercaptoben-zothiazoles, guanidines, dithiocarbamates, and thiurams (Fig. 32). Sulphenamides can also be used as accelerators for rubber vulcanization. A major change in the sulphur vulcanization was the substitution of lead oxide by zinc oxide. Zinc oxide is an activator of the accelerator system, and the amount generally added in rubber formulations is 3 to 5 phr. Fatty acids (mainly stearic acid) are also added to avoid low curing rates. Today, the cross-linking of any unsaturated rubber can be accomplished in minutes by heating rubber with sulphur, zinc oxide, a fatty acid and the appropriate accelerator. 

CoA dehydrogenase shows absolute specificity for the L-hydroxyacyl isomer of the substrate (Figure 24.16). (o-Hydroxyacyl isomers, which arise mainly from oxidation of unsaturated fatty acids, are handled differently.)... 

FIGURE 24.23 )3-Oxidation of unsaturated fatty acids. In the case of oleoyl-CoA, three /3-oxidation cycles produce three molecules of acetyl-CoA and leave m-AAdodecenoyl-CoA. Rearrangement of enoyl-CoA isomerase gives the tran.s-A species, which then proceeds normally through the /3-oxidation pathway. 

An Isomerase and a Reductase Facilitate the /3-Oxidation of Unsaturated Fatty Acids... 

Applications of peroxide formation are underrepresented in chiral synthetic chemistry, most likely owing to the limited stability of such intermediates. Lipoxygenases, as prototype biocatalysts for such reactions, display rather limited substrate specificity. However, interesting functionalizations at allylic positions of unsaturated fatty acids can be realized in high regio- and stereoselectivity, when the enzymatic oxidation is coupled to a chemical or enzymatic reduction process. While early work focused on derivatives of arachidonic acid chemical modifications to the carboxylate moiety are possible, provided that a sufficiently hydrophilic functionality remained. By means of this strategy, chiral diendiols are accessible after hydroperoxide reduction (Scheme 9.12) [103,104]. 

Figure 22-4. Sequence of reactions in the oxidation of unsaturated fatty acids, eg, linoleic acid. A -c/s-fatty acids or fatty acids forming A -c/s-enoyl-CoA enter the pathway at the position shown. NADPH for the dienoyl-CoA reductase step is supplied by intramitochondrial sources such as glutamate dehydrogenase, isocitrate dehydrogenase,and NAD(P)H transhydrogenase.

OXIDATION OF UNSATURATED FATTY ACIDS OCCURS BY A MODIFIED P-OXIDATION PATHWAY... 

Cowan Teeter (1944) reported a new class of resinous substances based on the zinc salts of dimerized unsaturated fatty acids such as linoleic and oleic acid. The latter is referred to as dimer acid. Later, Pellico (1974) described a dental composition based on the reaction between zinc oxide and either dimer or trimer acid. In an attempt to formulate calcium hydroxide cements which would be hydrolytically stable, Wilson et al. (1981) examined cement formation between calciimi hydroxide and dimer acid. They found it necessary to incorporate an accelerator, alimiiniiun acetate hydrate, Al2(OH)2(CHgCOO)4.3H2O, into the cement powder. 

A corrosion inhibitor with excellent film-forming and film-persistency characteristics is produced by first reacting Cig unsaturated fatty acids with maleic anhydride or fumaiic acid to produce the fatty acid Diels-Alder adduct or the fatty acid-ene reaction product [31]. This reaction product is further reacted in a condensation or hydrolyzation reaction with a polyalcohol to form an acid-anhydride ester corrosion inhibitor. The ester may be reacted with amines, metal hydroxides, metal oxides, ammonia, and combinations thereof to neutralize the ester. Surfactants may be added to tailor the inhibitor formulation to meet the specific needs of the user, that is, the corrosion inhibitor may be formulated to produce an oil-soluble, highly water-dispersible corrosion inhibitor or an oil-dispersible, water-soluble corrosion inhibitor. Suitable carrier solvents may be used as needed to disperse the corrosion inhibitor formulation. 

Lipids are hydrolyzed by moisture and heat into free fatty acids, though hydrolytic enzymes may be deactivated by extrusion. Also, unsaturated fatty acids may imdergo oxidative rancidity (Camire et al., 1990). 

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