Conjugated linoleic acid structure

On the other hand, BF3 (see Basic Protocol 1), as well as other acidic catalysts, will change the double-bond configuration of fatty acids that contain conjugated dienes. As research on conjugated linoleic acid (CLA) and other conjugated fatty acids becomes more popular, it is essential not to provide misinformation about compositional analysis due to improper application of a methylation protocol (Li and Watkins, 1998). The basic catalysts perform better on lipids rich in fatty acids with unique conjugated diene structures. Isomerization and artifacts are not produced when sodium methoxide or TMG are used as transesterification agents... 

Figure 3.1. Chemical structures of linoleic acid (cis-9, cis-12 18 2 A), trans-10, cis-12 conjugated linoleic acid (B), rumenic acid (cis-9, trans-11 conjugated linoleic acid C) and vaccenic acid (trans-11 18 1 D).

M. Hossen and E. Hernandez Enzyme-catalyzed synthesis of structured phospholipids with conjugated linoleic acid. European Journal of Lipid and Science and Technology 107 (2005) 730-736. 

Structural Characterization of Conjugated Linoleic Acid Methyl Esters with Acetonitrile Chemical Ionization Tandem Mass Spectrometry... 

Turini, M.E., and Martin, J.-C. (2001) Sources, Functions, and Analysis of Conjugated Linoleic Acid and Its Metabolites, in Structured and Modified Lipids, (Gunstone, F.D., ed.) pp. 251-284, Marcel Dekker, New York. 

FIGURE 5.1 Structures of tl0cl2-conjugated linoleic acid and c9tl 1-conjugated linoleic acid. 

FIGURE 2,2 Structure of cA-9,franj-ll-octadecadienoate (9c,llt-18 2), the major natural conjugated linoleic acid (CLA). 

Lipids are essential components in the diet and nutritionists should be more active in arguing the positive aspects of these molecules. They are required in their own right and also for the important minor components such as carotenoids, tocols, and sterols which accompany the oils and fats. The first chapter in the book is an overview of the development of functional foods and this is followed by chapters devoted to materials which are either lipids or are compounds that are fat-soluble and co-occur with oils and fats. These include carotenoids, tocopherols, phytosterols, omega-3 (n-3) oils, diacylglycerols, structured lipids, sesame oil, rice bran oil, and oils or preparations containing palmitoleic acid, y-linolenic acid, stearidonic acid, or conjugated linoleic acid. These topics will be of interest to those who produce lipids and those who seek to incorporate them into appropriate foods, and this book is directed primarily to these two groups. 

CLA refers to a mixture of positional and geometric isomers of linoleic acid (cis-9, cis-12 octadecadienoic acid) with a conjugated double bond system. The structure of two CLA isomers is contrasted with linoleic and vaccenic acids in Figure 3.1. The presence of CLA isomers in ruminant fat is related to the biohydrogenation of polyunsaturated fatty acids (PUFAs) in the rumen. Ruminant fats are relatively more saturated than most plant oils and this is also a consequence of biohydrogenation of dietary PUFAs by rumen bacteria. Increases in saturated fatty acids are considered undesirable, but consumption of CLA has been shown to be associated with many health benefits, and food products derived from ruminants are the major dietary source of CLA for humans. The interest in health benefits of CLA has its genesis in the research by Pariza and associates who first demonstrated that... 

What is important though is that the double bonds are separated by one and only one single bond. Remember the unsaturated fatty acid, linoleic acid, that you met in Chapter 3 Another fatty acid with even more unsaturation is arachidonic acid. None of the four double bonds in this structure are conjugated since in between any two double bonds there is an sp3 carbon. This means there is no p orbital available to overlap with the ones from the double bonds. The saturated carbon atoms insulate the double bonds from each other. 

LH symbolizes another molecule of linoleic acid in micelles. 9- and IS-HPODE are the main hydroperoxides formed, possessing a conjugated dienic structure. 

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