Oleic acid position

The diacids for these polymers are prepared via different processes. A2elaic acid [123-99-9] for nylon-6,9 [28757-63-3] is generally produced from naturally occurring fatty acids via oxidative cleavage of a double bond in the 9-position, eg, from oleic acid [112-80-1] ... 

Organisms differ with respect to formation, processing, and utilization of polyunsaturated fatty acids. E. coli, for example, does not have any polyunsaturated fatty acids. Eukaryotes do synthesize a variety of polyunsaturated fatty acids, certain organisms more than others. For example, plants manufacture double bonds between the A and the methyl end of the chain, but mammals cannot. Plants readily desaturate oleic acid at the 12-position (to give linoleic acid) or at both the 12- and 15-positions (producing linolenic acid). Mammals require polyunsaturated fatty acids, but must acquire them in their diet. As such, they are referred to as essential fatty acids. On the other hand, mammals can introduce double bonds between the double bond at the 8- or 9-posi-tion and the carboxyl group. Enzyme complexes in the endoplasmic reticulum desaturate the 5-position, provided a double bond exists at the 8-position, and form a double bond at the 6-position if one already exists at the 9-position. Thus, oleate can be unsaturated at the 6,7-position to give an 18 2 d5-A ,A fatty acid. 

Certain long-chain unsaturated fatty acids of metabolic significance in mammals are shown in Figure 23-1. Other C20, C22, and C24 polyenoic fatty acids may be derived from oleic, linoleic, and a-flnolenic acids by chain elongation. Palmitoleic and oleic acids are not essential in the diet because the tissues can introduce a double bond at the position of a saturated fatty acid. 

Powdered aluminium had been added to oleic acid. The mixture detonated after being prepared. Such an accident could not be repeated and it was thought that it was caused by the presence of a peroxide formed by the effect of air on oleic acid. In fact, the acid functional group has obviously nothing to do with the peroxidation. It is more likely that the chain s double bond that activates p hydrogen atoms (ally position) was involved in it. This is a well-known phenomenon since it is responsible for the rancidity of some oils and greases. 

Examples of this flipping mechanism are seen in cis-trans isomerizations from less stable to more stable isomers which when the reactions are carried out under deuterium. Already mentioned are the isomerizations of oleic acid. Additionally, methyl-(Z)-but-2-enoate isomerizes to its more stable E-isomer with incorporation of substantial amounts of deuterium during deuteriuma-tion over Pd/C (Fig. 2.16). At the same percentage deuteriumation, the saturated product contains in its P-position 90% of the two deuteriums added to... 

SCDs are a family of microsomal Fe-based metalloenzymes. They act on long-chain saturated acyl CoAs and introduce a ds-double bond at the C-9 or C-10 position. For example, SCDs convert stearic acid into oleic acid, and palmitic acid into palmitoleic acid. Monounsaturated FAs constitute a major component of TGs, cholesteryl esters, and phospholipids. The reaction requires molecular 02 and NADH and generates H20 in the process [3,4]. 

As mentioned earlier, oxidation of LDL is initiated by free radical attack at the diallylic positions of unsaturated fatty acids. For example, copper- or endothelial cell-initiated LDL oxidation resulted in a large formation of monohydroxy derivatives of linoleic and arachi-donic acids at the early stage of the reaction [175], During the reaction, the amount of these products is diminished, and monohydroxy derivatives of oleic acid appeared. Thus, monohydroxy derivatives of unsaturated acids are the major products of the oxidation of human LDL. Breuer et al. [176] measured cholesterol oxidation products (oxysterols) formed during copper- or soybean lipoxygenase-initiated LDL oxidation. They identified chlolcst-5-cnc-3(3, 4a-diol, cholest-5-ene-3(3, 4(3-diol, and cholestane-3 3, 5a, 6a-triol, which are present in human atherosclerotic plaques. 

Figure 7. Lipophilicity profile of propranolol in liposomes composed of zwitterionic and charged lipids (phosphatidyl ethanolamine (PE), oleic acid (OA), phosphatidyl inositol (PI)). Conditions of measurements are described in [113]. The dotted line indicates the partitioning profile of propranolol in the egg PC liposome system. The bars show the pH-dependent charge profile of propranolol (hatched bars positively charged propranolol) and the lipids in the membrane (black bars negatively charged lipids). Reprinted from [113] Kramer, S. (2001). Liposome/water partitioning , In Pharmacokinetic Optimization in Drug Research, eds. Testa, B. et al. Reproduced by permission of Verlag Helvetica Chimica Acta, Zurich...

A mixture of sorbitan derivatives named Tween 81 specified as ethoxylated sorbitan esters containing oleic acid, was examined by APCI-FIA-MS and —LC—MS in the positive and negative modes. APCI-MS ionisation was supported by the addition of ammonium acetate resulting in equal spaced (Am/z 44) [M + NH4]+ ions which, in parallel, suppressed [M + Na]+ ions. The FIA—MS(+) spectrum contained ions with m/z between 358 and 974 while negative ionisation led to a series of ions from 399 to 971, Am/z 44 equally spaced, too. 

Odor and color stability problems were also related to the alkyl chains used for SAI. These could be traced to the oxidation of unsaturated carbons, such as oleic acid (Ci8 fatty acid with a single double bond between carbon 9 and 10, i.e. bond position 9 counted from the carboxyl carbon), linoleic acid (Cis fatty acid with two double bonds at position 9 and 12), and linolenic acid (Cis fatty acid with three double bonds at position 9, 12, and 15). Natural coconut fatty acid contains about 6% oleic acid, about 3% linoleic acid, and less than 1% linolenic acid. Tallow fatty acid contains nearly 44% oleic and about 6% of other unsaturates [20]. Partial hydrogenation of the coconut fatty acid used in the manufacture of SCI served to eliminate linoleic and linolenic acids for improved odor stability, while not eliminating oleic acid, which is important for good lather. 

Tran. -isomers are much rarer than cis-isomers. Many different positional isomers of monoenoic acids may be present in a single, natural lipid and this is not a comprehensive list. Palmitoleic and oleic acids are quantitatively the commonest unsaturated fatty acids in most organisms. Odd-chain monoenoic acids are minor components of animal lipids but are more significant in some fish and bacterial lipids. 

For unsaturated fatty acids, we need to indicate where the double bonds are. We do this by numbering the carbon atoms, starting at the carboxyl end, and designating the position of the double bonds by the number of the carbon atom closest to the carboxyl end of the molecules. One example will suffice to illustrate the point. Properly numbered oleic acid (cw-9-octadecenoic acid) is ... 

Figure 11.10 Structure of ds-octadecenoic and trans-octadecenoic add (an example o/cis-trans isomerism). The common name for trans-octadecenoic acid is elaidic acid it is one of the few naturally occurring trans fatty acids. The common name for c/s-octadecenoic acid is oleic acid. Note that the two hydrocarbon chains are separated by the double bond which prevents rotation of the position of the two chains. The structure of the trans fatty acid is biochemically unusual and therefore biochemically excluded. ...

If the substrate is fully saturated, the first double bond is always inserted at position 9 by the A desaturase (so that, for example, stearic acid (18 0) is converted to oleic acid (18 co-9). Thus the A desaturase requires the presence of a cis double bond at position 9 before it can catalyse desaturation at position 6. Animals do not possess a desaturase that can insert a double bond at a position greater than nine. (Such desaturations are present in plants). It is this fact that determines that such unsaturated fatty acids must be provided in the diet, i.e. they are essential. 

Due to the specificities of the acyltransferases in the pathways, the fatty acid at position one of glycerol is saturated whereas that at position 2 is monounsaturated (e.g. oleic acid), although in most glycerophospholipids, the fatty acid at position 2 is polyunsaturated (e.g. arachidonic or eicosapentaenoic acids). This is important for the... 

The sources of these fatty acids in the cells are those that are present at position 2 of the membrane phospholipids. The proportion of these two in the phospholipid depends to a large extent on the type of fatty acids in the triacylg-lycerol in the diet, that is, the amount of the omega-6 (lin-oleic acid) and that of the omega-3 (a-linolenic acid). 

Oxidation of oleic acid to 10-hydroxyoctadecanoic acid by a gram-positive bacterium was described with a transformation yield of 65% at a concentration of 50 g oleic acid after 72 h in a medium containing Tween 80 [232]. The hydroxy fatty acid can be converted to 4-dodecanolide, an important coconut-fruity like lactone, by -oxidation with yeasts, affording a total lactone yield of about 20% from oleic acid [222, 232]. 

In the group with positive spreading coefficients (e.g., toluene-in-water and oleic acid-in-water emulsions), the values ofkj a in both stirred tanks and bubble columns decrease upon the addition of a very small amount of oil, and then increase with increasing oil fraction. In such systems, the oils tend to spread over the gas-liquid interface as thin films, providing additional mass transfer resistance and consequently lower k values. Any increase in value upon the further addition of oils could be explained by an increased specific interfacial area a due to a lowered surface tension and consequent smaller bubble sizes. 

In a very similar way, acyl-enzyme formation depends upon the unsaturation level of the chains, and upon the position of the double bond(s) on the chains. Geotrichum candidum lipase is known to prefer fatty acids with a double bond on the C9. like oleic acid. 

The oxidative stability of an oil depends on the fatty acid (FA) composition and triacyl-glycerol (TAG) structure, as well as on non-TAG components, such as tocopherols, carotenoids, ascorbic acid, citric acid, free fatty acids, and sterols, which may either prevent or promote oxidation. Several investigations have reported correlations of FA composition, TAG structure, and oxidative stability (135-140). For example, the oxidative stability of purified TAG from soybean oil (SBO) in air in the dark at 60°C is correlated positively with a greater concentration of oleic acid (O) and lower concentrations of linoleic (L) and linolenic (Ln) acids of SBO TAG. 

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