Minor fatty acids arachidonic acid

Physiological Function of n-6 DPA Reported to Date. Not only is the occurrence of n-6 DPA rare in the biosphere it is also a minor fatty acid in mammals. Of the n-6 essential fatty acids (EFA) for primates or humans, linoleic acid (LA, 18 2n-6) and arachidonic acid (AA, 20 4n-6) are the most prominent and important. Among the docosapolyenoic acids (22-carbon chain), which can cross the blood-brain barrier more than the eicosapolyenoic acids (20-carbon), DHA (an n-3 EFA) is the most important. In mammals, the levels of n-6 DPA in brain and retina increase in accordance with n-3 essential fatty acid deficiency (EFAD). Is the increase only compensatory for DHA or does n-6 DPA have any positive physiologic functions ... 

Arachidic acid produces 134 moles of ATP/mole, whereas arachidonic acid gives 126 moles of ATP/ mole of fatty acid. This difference in ATP quantities is rather minor. Therefore any biological difference caused by dietary saturated versus unsaturated fats being due to their ATP yields is unlikely. 

There are about 200 minor monoenoic, dienoic and polyenoic fatty acids in milk fat ranging in chain length from C10 to C24, and consisting of both positional and cisltrans isomers. A number have considerable nutritional significance for example, eicosapentaenoic acid (20 5,0.09%) and docosahex-aenoic acid (22 6,0.01%) are present in the metabolic pathway of the n-3 fatty acids, while arachidonic acid (20 4, 0.14%) is part of the n-6 pathway. 

Eicosanoids are a class of lipids that include the prostaglandins, thromboxanes, and leukotrienes. Eicosanoids derive their name from their common origin, that is, from C20 polyunsaturated fatty acids, the eicosaenoic acids, particularly arachidonic acid (all-cw-5,8,ll,14-eicosatetraenoic acid). Related trienoic and pentaenoic acids are minor precursors to some of these compounds. 

About half of all fatty acids are PUFAs. The major PUFA is linoleic acid (18 3) that is about 7 times more frequent than arachidonic (20 4) or doc-osahexaenoic acids (22 6) (J9). Many of the products that have been measured are largely from arachidonic acid that represents a minor constituent of the lipoproteins. Each oxidation product listed in Table 1 is considered in the following text, and apparent normal reference ranges for some of them are listed in Table 2 along with the source from which the information was derived. 

---