Fatty acids positional isomers

In a partially hydrogenated fat, the number of fatty acid isomers is dramatically increased by the appearance of geometrical isomers (i.e., cis and trans configurations) and various positional isomers (i.e., different positions of double bonds within the fatty acid chain). Thus the in-... 

Complete resolution and quantitation by HPLC of mixtures of monohydroxy fatty acids containing positional isomers of various chain lengths is a technical problem, because their separation occurs according to both chain length and the position of the hydroxyl group on both reverse-phase and silica adsorption HPLC columns. 

The acetal ester does not trimerize and can be stored for years before hydrolysis and use34. The deuterium-labelled fats have been needed in multigram quantities for studies of the metabolism of configurational and positional fatty acid isomers in humans. 

During the course of transformation of the unsaturated fatty acids to saturated fatty acids, positional isomers of unsaturated fatty acids are produced. These unsaturated fatty acid isomers are known as trans-fatty acids (62), as shown in Figure 6. 

Emken EA. Nutrition and biochemistry of trans and positional fatty acid isomers in hydrogenated oils. Ann Rev Nutr 1984 4 339-376. 

In summary, it appears that the positional isomers of docosenoic acid are equivalent in their cardiopathogenic properties, and to date there is no convincing evidence that real differences exist when fish oils or rapeseed oils, with the same concentration of docosenoic fatty acid isomers are fed to rats. 

Lipoxygenation of PUFA can result in a range of positional hydroxyl fatty acid isomers that have been shown to exhibit a range of bioactivities. When AA is the main PUFA substrate, a range of HETE are formed (Figure 3.3). 

Dutton, H. and Emken, E.A. (1979) Geometrical and Positional Fatty Acid Isomers, American Oil Chemists Society, Champaign. 

Correa, R.A., Ferras, V., Medvedovici, A., Sandra, P., Ceme, K., and David, F. (1999) Positional and Configurational Separation of Fatty Acid Isomers by Micro Reversed-Phase Liquid Chromatography with an Ag -containing Mobile Phase, J. Chromatogr. A... 

Fatty acid atoms position Isomer Trivial name... 

Table I lists all the polyunsaturated fatty acids, including positional isomers, which have been detected in higher protists. Doubtless the list will be considerably extended with time, when more authors adopt the painstaking approach of Kom to the analysis of the fatty acids of protists, as exhibited in his study of Euglena. Kom (1964b) detected fifty-one difiFerent fatty acids in this flagellate alga, including thirteen which had not been detected previously in algae.

There are a myriad of possible isomers, including positional and geometrical isomers of the double bond(s) as well as stmctural isomers resulting from head-to-head or head-to-tad alignment of the reacting fatty acids. 

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