Fatty acids families

Important essential fatty acids in the diet are linoleic acid (cis,cis-9,12-octadecadienoic acid, 18 2d9,12) and a-linolenic acid (all-cis-9,12,15-octadecatrienoic acid 18 3d9,12,15). The numbering in this conventional system begins with the carboxyl group. The "short hand," for example 18 2d9,12, indicates 18 carbon atoms, with two double bonds located between carbon atoms 9 and 10 and 12 and 13. There is an alternative system of numbering in which fatty acids are numbered from the methyl (or a>) terminal. In this case, linoleic acid is designated a>-6,9-octadecadienoic acid (18 2ft)6), and a-linolenic acid is o>-3,6,9-octadecatrienoic acid (18 3ft)3). This serves to designate two unsaturated fatty acid families, the ft)6 and the a families. 

By elimination of erucic acid from traditional high erucic acid rapeseed, the C22 fatty acid family also was eliminated. The replacement canola (low-erucic-acid rapeseed) had one less variety of fatty acids, and became a /3 crystallizer. 

TABLE 14. Melting Characteristics of the Octadecanoic Fatty Acid Family. 

TABLE 12. Members of Polyenoic Fatty Acid Families. ... 

FIGURE 10.2 Unsaturated fatty acid families and their importance in the formation of eicosanoids and long-chain PUPA (LCPUFA). 

The polyunsaturated fatty acids family is widely distributed throughout nature. They have several double bonds in the principal chain. Common dienoic acids are ds-,ds-9,12-octadecadienoic acid (lioleic acid), /ra s-,/ra s-9,12-octadecadienoic acid (line-laidic acid), 5,9-heneicosadienoic acid, 5,9-do-cosadienoic acid, and 5,9-tricosadienoic acid. 

Some synthetic pesticides and drugs have a phenyl or a naphthyl ring attached to the principal chain of fatty acids. The phenoxy acid pesticides, which are derivatives of formic, acetic, propionic, or butyric acids, belong to the synthetic fatty acids (SFAs) family. These acids are usually referred to as phenoxy acids and not as fatty acids, although they should be included in the fatty acids family, because they are derivatives of fatty acids. One such example is (2-methyl-4-chlorophenoxy)acetic acid (Figure 16). 

An example of the thio fatty acid family is tetrad-ecylthioacetic acid (CH3-(CH2)i3-S-CH2-COOH). 

Essential fatty aids (EFA) are required for the structure of cell membranes, reproduction, growth, and the regulation of cell function via a group of hormone-like derivatives, the eicosanoids. These properties of EFA are more important than other nonessential functions [19]. EFA can be allocated to two fatty acid families according to the position of the first double bound from the methyl end at carbon 3 or carbon 6, the most important representatives being linoleic acid (C18 2 co-6) and a-linolenic acid (C18 3 0)-3). In contrast, oleic acid (C18 1 (o-9) and its derivatives with the first double bound at carbon 9 can be synthesized in the body and are not essential. 

The A6 desaturation of unsaturated acyl-CoA is the first reaction involved in the normal biosynthesis of all polyunsaturated fatty acids families in animal microsomes. Due to this key position it can regulate the biosynthesis of the fatty acids of the series. The reaction is modified by competition with substrates and products, ATP, and acyl-CoA acceptors. 

PUFA) present in brain are arachidonic acid (20 4 A5,8,11,14) of the linoleic acid series and especially docosahexaenoic acid (22 6 A4,7,10,13,16,19) of the linolenic acid series. The higher levels of 22 6 in brain, in comparison with other tissues, suggest a special function of the n-3 fatty acid family in nervous system. 

The possibility that the modification of the cooperativity was due to direct action of some fatty acid family was excluded since no correlation could be established between the value of n and the amount of the members of any of the fatty acid families (n - 3),... 

It is evident from the pathway shown in Figure 2 that there is competition between the n-9, n-6 and n-3 fatty acid families for metabolism. The A -desaturase reaction is rate limiting in this pathway (British Nutrition Foundation, 1992). The preferred substrate for A -desaturase is a-linolenic acid, followed by linoleic acid followed by oleic acid (British Nutrition Foundation, 1992). However, because linoleic acid is much more prevalent in most human diets than a-linolenic acid (see Section F.2 on fatty acid intakes in humans), the metabolism of n-6 fatty acids is quantitatively more important. Note, too, that... 

Essentially, as described in Chapter 2, this class of lipid species as a member among the modified fatty acid family can be readily ionized in the negative-ion mode of ESI-MS to produce deprotonated molecular ions (i.e., [M-H] ) as demonstrated [54], Product-ion ESI-MS analysis of their deprotonated molecular ions after CID shows the following fragmentation pattern [54] ... 

Humans are unable to insert a double bond at the n-3 position of a fatty add of 18 carbons in length or a cis double bond at the n-6 position of a fatty acid chain therefore, co-3 and co-6 fatty adds are essential nutrients. a-Iinolenic and linoleic acids are the precursors of other polyimsaturated fatty adds of the co-3 and co-6 fatty acids family. The fiver is the primary site for the metabolism of essential fatty acids and where the synthesis of arachidonic acid (20 4co-6) from finoldc acid and EPA (20 5co-3) and DHA (22 6co-3) from a-linolenic acid takes place. However, other tissues experience metabolism of these fatty adds. For instance, the desaturase enzymes ocxnn in the endoplasmatic reticulum tissues of the intestinal mucx)sa, brain, and retina."" The metabolism of co-6 fatty acids involves the synthesis of... 

Long and short spacings of the NIE and CIE LCO and POSBO blends were determined by powder X-ray diffraction (XRD). Diffraction patterns of natural fats produce broader peaks than pure compounds (e.g., tristearin) owing to the presence of multiple fatty acid families within the unit cells (Timms, 1980) and the presence of oil. Lard has been reported to be a P-tending fat, whereas PO has been reported to be a P -tending fat (deMan et al., 1991 Wiedermann, 1978). 

The fact that the A6-desaturase can introduce its double bond at position 6 into the first member of each fatty acid family (n-3, n-6, n-7 and n-9) has extremely important consequences. All four precursors can compete for desaturation by the same enzyme as illustrated in Figure 5.2. The affinity of the substrates for the A6-desaturase is in the order 18 3 > 18 2 > 18 1. In man and many other mammals, the most important metabolic pathway is the one in which linoleic acid is converted into arachidonic acid. Normally, the diet contains sufficient linoleic acid for this pathway to be able continually to supply the quantity of arachidonic acid needed by body tissues. There are circumstances when this is not so, however ... 

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