Omega-labeled fatty acids

The last carbon of the chain is called the M-carbon (omega-carbon), so the attached phenyl group is an co-phenyl group, (a) Oxidation of co-phenyl-labeled fatty acids occurs two carbons at a time. Fatty acids having an even number of carbon atoms are degraded to phenyl acetate and "acetate." (b) Oxidation of cophenyl-labeled fatty acids that contain an odd number of carbon atoms yields benzoate and "acetate."... 

Oxidation is a cyclical pathway which removes a C2 (acetyl) unit form the fatty acyl-CoA on each cycle. The designation [3 derives from the traditional system of labelling atoms within fatty acid molecules where the carbon attached to the carboxyl group is a and the methyl carbon is always CO (omega) ... 

Table 5 shows the marketing and label strategies for some current marine omega-3 products sold in Halifax, Canada. Obviously samples No. 1 and No. 6 are natural oils. Perhaps No. 5 is simply winterized oil, a process demonstrated in Table 6 for menhaden oil, which follows from the tendency for DHA to be in the 2-position of fish oil triacylglycerols (81). EPA is reputed to be somewhat less specihc. In the absence of 20 1 and 22 1, the outer 1- and 3-positions may, in some molecules, present two saturated fatty acids from 14 0, 16 0, and 18 0 in one triacylglycerol molecule, which leads to the stearine composition of Table 6. 

Analysis of fatty acids (FAs) may be required for a variety of reasons. It maybe important in food process control, quality assurance, detection of adulteration, or for regulatory reasons such as labeling. In the biological field, information on the FA composition in blood and tissues may be important for nutritional and health reasons—especially for FAs of functional significance (e.g., long-chain omega-3 acids)— or for the diagnosis of some metabolic diseases. 

Stearic acid (octadecanoic acid) is a waxy solid that is a component of animal and vegetable fats (see illustration). Stearic acid is used in cosmetics, as a dietary supplement, and to make candles. Arachidic acid (eicosanoic acid) is found in peanut oil as well as in fish oil. Certain terminology can be used, particularly for fatty acids that are found in nature. The carboxylic acid end is polar, associated with water solubility, and is labeled the delta (A) end of the fatty acid. The methyl end is associated with being nonpolar and more soluble in oils and is labeled the omega (O) end (see the labels in 92). 

Additional nomenclature for the unsaturated fatty acids is used to identify the site of C=C units relative to the terminal methyl group (the omega end). Because the closest double bond to the methyl group in palmitoleic acid (96) is 7 carbon atoms away from the methyl, palmitoleic acid is called an omega-7 ((0-7 or n-7) fatty acid. For a-linolenic acid (99), the double bond closest to the methyl group is only 3 carbons away, so it is an omega-3 ((0-3 or n-3) fatty acid. Several other acids are suitably labeled. 

Linoleic acid has 18 carbons in its chain. The carbon next to the carbonyl is labeled a (alpha) and the others are labeled sequentially by Greek letters. By convention, the last carbon in the chain (whatever the chain length) is named after the last Greek letter, o) (omega). The bonds are numbered from the (0 end, and if there is a double bond at the 6th bond, as in linoleic acid, it s called a 0)-6 fatty acid... 

The fatty-acid profile of Omega-9 Oils is typically high in oleic, low in linolenic and relatively low in saturated fat. This allows for both a low-saturated fat and trans-fat free (per serving size of 15 mL) label claim in the United States. 

---