Isomeric fatty acids

The clay-cataly2ed iatermolecular condensation of oleic and/or linoleic acid mixtures on a commercial scale produces approximately a 60 40 mixture of dimer acids and higher polycarboxyUc acids) and monomer acids (C g isomerized fatty acids). The polycarboxyUc acid and monomer fractions are usually separated by wiped-film evaporation. The monomer fraction, after hydrogenation, can be fed to a solvent separative process that produces commercial isostearic acid, a complex mixture of saturated fatty acids that is Hquid at 10°C. Dimer acids can be further separated, also by wiped-film evaporation, iato distilled dimer acids and trimer acids. A review of dimerization gives a comprehensive discussion of the subject (10). 

On the basis of th6 following nmr spectra, assign likely structures to the isomeric fatty acids, CC and DD, of formula C17H35COOH. 

Ru. Platinum, Pd, and Ni catalysts isomerize fatty acids. Platinum produces less isomerization than Pd and this advantage can be increased in an appropriate solvent, e.g., over Pd on carbon isomerization of cw-cyclododecene occurs, whereas over Pt on carbon saturation is observed, both reactions being conducted in CCl4 . ... 

Since hydrogenation is not carried to completion there is considerable scope for isomerization to occur. The mechanism by which this takes place has been described by Allen and Kiess (1955). They indicate that selective conditions tend to favor isomer formation. Both positional and geometric isomers are formed. In positional isomers, double bonds have wandered from their original position along the fatty acid carbon chain in geometric isomers the position of groups attached to carbon atoms have changed relative to each other in space from the natural cis to trans. Recently the nutritional properties of isomeric fatty acids have been questioned. Applewhite (1981) in a literature review has concluded that this concern is not substantiated by the available data. 

Bovine milk fat has been reported to contain 400 or more fatty acids (1). Caprine and ovine milk fats have not been as extensively examined but could be assumed to contain a similar number of fatty acids since the ruminal processes are similar in these two species. Humans have been consuming these fatty acids in meat and milk products since prehistory when ruminant species became food sources for mankind. The variety and chemical composition of milk lipids is truly amazing. Within the last hundred years many lipid classes, individual fatty acids, and isomeric fatty acids have been identified as analytical capabilities increased. Recent advances in technology have allowed the identification and characterization of specific isomers of fatty acids present in milk fat that contain single cis or trans double bonds (monoenes) and conjugated double bonds (CLA) with none, one, or two trans bonds. These techniques of gas chromatography and HPLC with silver ion columns are described in Volumes 1 and 2 of this series. 

Planner, R.D. and Gardner, H.W. Mass spectrometry of isomeric fatty acid hydroperoxides by chemical ionization via direct exposure probe. Lipids 20,126-131 (1985). 

The object of the work [72] was to produce, for the authors own use, highly polar SCOT capillary columns capable of separating isomeric fatty acid methyl esters several solid supports and techniques were tested. 

Solvents. Table 71 contains solvent mixtures suitable for fractionating the most important lipid classes. Besides these solvents, the following have also been often used the methyl esters of unsaturated, positionally isomeric fatty acids have been separated from one another by triple development at —15° C using toluene [142] triglycerides have been fractionated with chloroform-carbon tetrachloride-methanol-acetic acid (50 -I- 50 + 1.5 -1- 0.5) [6, 7]. The separation of lecithins on silica gel H, impregnated with silver nitrate [5], is very satisfactory using chloroform-methanol-water (65 -1- 25 + 4) [5] (see also [57, 88]). 

Hunter, J.E. (1992) Safety and health effects of isomeric fatty acids, in Fatty Acids in Foods and Their Health Implications, ed. C.K. Chow, Marcel Dekker, New York, pp. 857-868. 

Hudgins, L.C., Hirsch, J. and Emken, E.A. (1991) Correlation of isomeric fatty acids in human adipose tissue with clinical risk factors for cardiovascular disease. Am. Soc. Clin. Nutr. 53, 474-482. 

Cell suspension cultures of soya were incubated with mixtures of positional and geometrical isomers of [l- C]octadecenoic acids in order to determine enzymatic specificities for the incorporation of individual isomeric fatty acids into the glycerolipids, for instance triacylglycerols [60]. It is obvious from the data given in Table 3 that A9 isomers of both mixed substrates, (Z)-and f J-octadecenoic acids, are preferentially incorporated into the sn-2 position of the glycerol backbone, whereas a much lower percentage of these acyl moieties are esterified to the... 

Valeric Acid vo- lir-ikT n Pentanoic Acid, [valerian fr. Its occurrence in the roof of valerian] (1857) Any of four isomeric fatty acids or a mixture of these a liquid acid of disagreeable odor obtained from valerian or made synthetically and used in organic synthesis. 

When the diet contains a small, but normally adequate, amount of linoleic acid which is swamped by enormous amounts of other fatty acids in the diet (e.g. oleic acid or isomeric fatty acids, section 8.15.3). In this situation, the fatty acids in excess compete successfully with linoleic acid for the A6-desaturase and generate a series of polyunsaturated fatty acids that have no essential fatty acid activity and cannot substitute for the linoleic acid family. The effect of this competition is illustrated in Figure... 

Gurr, M.I. (1987) Isomeric fatty acids. Biochemical Society Transactions, 15, 336-338. 

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