Linolenic acid reactions

Detailed accounts of the biosynthesis of the prostanoids have been pubUshed (14—17). Under normal circumstances arachidonic acid (AA) is the most abundant C-20 fatty acid m vivo (18—21) which accounts for the predominance of the prostanoids containing two double bonds eg, PGE2 (see Fig. 1). Prostanoids of the one and three series are biosynthesized from dihomo-S-linolenic and eicosapentaenoic acids, respectively. Concentrations ia human tissue of the one-series precursor, dihomo-S-linolenic acid, are about one-fourth those of AA (22) and the presence of PGE has been noted ia a variety of tissues (23). The biosynthesis of the two-series prostaglandins from AA is shown ia Eigure 1. These reactions make up a portion of what is known as the arachidonic acid cascade. Other Hpid products of the cascade iaclude the leukotrienes, lipoxins, and the hydroxyeicosatetraenoic acids (HETEs). Collectively, these substances are termed eicosanoids. 

Conjugation as well as geometric and positional isomerization occur when an alkadienoic acid such as linoleic acid is treated with a strong base at an elevated temperature. CycHc fatty acids result from isomerization of linolenic acid ia strong base at about 250°C (58). Conjugated fatty acids undergo the Diels-Alder reaction with many dienophiles including ethylene, propylene, acryUc acid, and maleic anhydride. 

Diethylenetriaminepentaacetic acid DFMO al-Difluoromethyl ornithine DFP Diisopropyl fluorophosphate DFX Desferrioxamine DGLA Dihomo-y-linolenic acid DH Delayed hypersensitivity DHA Docosahexaenoic acid DHBA Dihydroxybenzoic acid DHR Delayed hypersensitivity reaction... 

Reaction yields depend on the nature of the substrate. Linseed oil contains two polyunsaturated fatty acids 50% linolenic acid and 18% linoleic acid. The corresponding hydroperoxides are obtained with low yields. 

Potato LOX has the potential to be used as an alternative model to the mammalian enzyme because of its great availability(Lopez-Nicolas and others 2000). To date, three isoenzymes of potato LOX have been isolated. Several works have reported linoleic acid as the optimum substrate for potato LOX-1, 9-hydroperoxide being the main product of the reaction. Another LOX substrate, linolenic acid, has been reported as the preferred substrate for both potato LOX-2 and -3, which produce 13-hydroperoxide as the main product. 

The question arises whether inhibition of the desaturase for this particular pathway can be overcome. The answer is yes. The product of the A desaturase when desaturating linoleic acid is y-linolenic acid. Supplementation of the diet with y-linolenic acid, which bypasses the A desaturase reaction, has been used to increase the formation of dihomo-y-linolenic acid and arachidonic acid (Figure... 

The absorbance value now recorded is the amount of ozone absorbed by the system between the sample and reference cuvettes. Most of this is due to breakdown of ozone in the alkaline solution contained in the reaction vessel. If this solution is replaced by 1 N NaOH, absorbance at this point is much higher when the solution is 0,1 N HCl, absorbance is very low. This corresponds with the known rate of ozone breakdown as a function of pH ( 9 ), If linolenic acid (Sigma chemical, 99% pure, C18 3 (9c, 12c,... 

The amount of TBA reactant can be converted into moles of malondialdehyde by the extinction coefficient of 155 mM cm ozone (22), and the yield of this reaction, or ratio of malondialdehyde/ozone taken-up, is shown in Figure 9. Notice that the yield for ozone-treated linolenic acid varies with time of reaction from about 3% to over 30%. These results differ from those for lipid peroxidation reactions which also give rise to malondialdehyde but have yields of 2-5% (23). 

The speed of reaction of O3 with linolenic acid and DTT measured by this chemical system indicates that unsaturated fatty acid and sulfhydryls react nearly equally if present in the same concentration (100 yM) in an aqueous medium. The questions then are (a) are sulfhydryls and unsaturated fatty acids equally... 

The volatiles produced by the LOX pathway and autoxidation are typically volatile aldehydes and alcohols responsible for fresh and green sensorial notes. In the LOX pathway these volatile compounds are produced in response to stress, during ripening or after damage of the plant tissue. The pathway is illustrated in Scheme 7.2. Precursors of the LOX (EC 1.13.11.12) catalysed reactions are Cis-polyunsaturated fatty acids with a (Z,Z)-l,4-pentadiene moiety such as linoleic and a-linolenic acids that are typically oxidised into 9-, 10- or 13-hydro-peroxides depending on the specificity of the LOX catalyst. These compounds are then cleaved by hydroperoxide lyase (HPL) into mainly C, C9 and Cio aldehydes, which can then be reduced into the corresponding alcohols by alcohol dehydrogenase (ADH EC 1.1.1.1) (Scheme 7.2) [21, 22]. The production of volatile compounds by the LOX pathway depends, however, on the plants as they have different sets of enzymes, pH in the cells, fatty acid composition of cell walls, etc. 

Rapeseed oil and its fatty acids (stearic, palmitic, oleic, linoleic, and linolenic acids) were chosen as the samples of vegetable oil. The experiments were performed in the batch- and flow-type supercritical biomass conversion systems developed in our laboratory. For the batch-type system, a reaction vessel was made of Inconel-625 with a volume of 5 mL for the flow-type system, the supercritical treatment tube was constructed from Hastelloy stainless steel (HC 276) with length of 84 m and an id of 1.2 mm, with the total volume being about 95 mL. Detailed information about the equipment can be found elsewhere (13). 

Fell et al. presented a micellar two-phase system in which fatty acid esters can be hydroformylated [30]. Short fatty acids react in a mixture of water and the substrate without adding any surfactants. The rhodium/NaTPPTS catalyst system was able to conduct the reaction of methyl 10-undecenoate at 100°C with 30-bar synthesis gas pressure with a conversion of 99% without any surfactant. The reaction of linolenic acid ester was hindered by phase transfer problems which could be overcome by employing surfactants. The addition decreased the reaction time, so the same rhodium catalyst could achieve a conversion for linolenic methyl ester of 100%. The authors... 

An interesting system that is applied in the epoxidation of soybean oil is MTO immobilized on niobia combined with UHP as oxidant. The different components of soybean oil have been studied separately, and it was found that oleic acid can be epoxidized completely with 1 mol% MT0/Nb205 in 2 h at room temperature. When raising the temperature to 50°C and lowering the catalyst amount to 0.2 mol%, complete epoxidation is reached in as little as 10 min. In applying the same procedure to linoleic and linolenic acid, excellent yields of epoxidized product are obtained within 30 min. In attempts to reuse the catalyst in this reaction, it was found that the catalyst remains active for three runs, although no numerical data is provided to underline this [39, 76]. 

Write the formulas of the reaction, converting linolenic acid to its methyl ester. 

Molecular oxygen, as distinct from reactions involving radicals or singlet oxygen, is directly inserted into free fatty acids by lipoxygenase (LOX) enzymes. Lipoxygenases, both regio- and stereospecific enzymes, react on the 1,4-pentadienyl moieties such as those of linoleic and a-linolenic acids. 

Cw-polyenoic acids are present at low concentrations in milk fat, because of the biohydrogenation reactions that take place in the rumen. These acids are comprised almost exclusively of linoleic acid (9c, 12c-18 2), about 1.2 to 1.7% and a-linolenic acid (9c, 12c, 15c-18 3), about 0.9 to 1.2% (Table 1.2). These two fatty acids are essential fatty acids they cannot be synthesised within the body and must be supplied by the diet. In recent times, the usage of the term essential has been extended to include derivatives of these fatty acids, which are not synthesised in significant quantities (e.g., eicosapentaenoic acid, 20 5 and docosahexaenoic acid, 22 6). The proportion of a-linolenic acid appears to be affected by the cow s diet the concentration is higher in milk from pasture-fed cows than in milk from barn-fed cows (Hebeisen et al., 1993 Wolff et al., 1995). In the case of linoleic... 

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