Arachidonic acid vegetable oils

CifiHjjOi. A fatly acid which is easily oxidized in air.-It occurs widely, in the form of glycerides, in vegetable oils and in mammalian lipids. Cholesieryl linoleale is an important constituent of blood. The add also occurs in lecithins. Together with arachidonic acid it is the most important essential fatty acid of human diet. 

Prostaglandins arise from unsaturated C20 carboxylic acids such as arachidonic acid (see Table 26 1) Mammals cannot biosynthesize arachidonic acid directly They obtain Imoleic acid (Table 26 1) from vegetable oils m their diet and extend the car bon chain of Imoleic acid from 18 to 20 carbons while introducing two more double bonds Lmoleic acid is said to be an essential fatty acid, forming part of the dietary requirement of mammals Animals fed on diets that are deficient m Imoleic acid grow poorly and suffer a number of other disorders some of which are reversed on feed mg them vegetable oils rich m Imoleic acid and other polyunsaturated fatty acids One function of these substances is to provide the raw materials for prostaglandin biosynthesis... 

Rats fed a purified nonlipid diet containing vitamins A and D exhibit a reduced growth rate and reproductive deficiency which may be cured by the addition of linoleic, a-linolenic, and arachidonic acids to the diet. These fatty acids are found in high concentrations in vegetable oils (Table 14-2) and in small amounts in animal carcasses. These essential fatty acids are required for prostaglandin, thromboxane, leukotriene, and lipoxin formation (see below), and they also have various other functions which are less well defined. Essential fatty acids are found in the stmctural lipids of the cell, often in the 2 position of phospholipids, and are concerned with the structural integrity of the mitochondrial membrane. 

The LA and ALA are mainly obtained from PUFA-rich vegetable oils. LA is found in high concentration in several oils including safflower, corn, and soybean, while ALA is found in linseed, canola, and soya bean.11 Although most of the n-6 requirement is obtained from dietary LA, small amounts of its longer chain metabolite arachidonic acid (AA) may be ingested from food of animal origin,... 

Prostaglandins arise from unsaturated C2o-carboxylic acids such as arachidonic acid (see Table 24.1). Mammals cannot biosynthesize arachidonic acid directly. They obtain linoleic acid (see Table 24.1) from vegetable oils in their diet and extend the carbon chain of linoleic acid from 18 to 20 carbons while introducing two more... 

Linoleic acid (LA) is a polyunsaturated fatty acid used in the biosynthesis of arachidonic acid (AA) and thus some prostaglandins. It is found in the lipids of cell membranes. It is abundant in many vegetable oils, comprising over half (by weight) of poppy seed, safflower, sunflower, and com oils. 

The fats of the diet serve as a source of the essential fatty acids—arachidonic, linoleic, and linolenic acid, but only linoleic acid is required preformed in the diet. Although meats provide fat, the vegetable oils are generally richer sources of the essential fatty acids than animals fat hence, no deficiency of fatty acids is likely to develop in a meatless diet unless there is impaired lipid absorption. 

Examples of dietary omega-6 FAs are linoleic add (C,g2) and arachidonic acid (C20 4)- The major dietary sources of linoleic acid are vegetable oils, and linoleic acid may be converted to arachidonic add in diverse cells prior to its conversion to prostaglandins of the 2 series. 

Essential fatty acids or polyunsaturated fatty acids include linoleic acid, Ot-linolenic acid (and probably arachidonic acid in children). They must be taken in the diet, and are found in fish and vegetable oils. They contain C03 or C06 bonds (see page 29). 

Polyunsaturated fatty acids are ultimately derived from plants, seed, leaves, and phytoplankton. Terrestrial food chains (i.e., edible plants and animal fat) contain primarily linoleic acid (Table 3, Fig. 2), an polyunsaturated fatty acid, and only very small amounts of cu-3 polyunsaturated fatty acids (nearly exclusively CK-linolenic acid). Fatty acids in land plants are not chain-elongated above the 18-carbon level. In mammalians, the polyunsaturated 18-carbon eu-6 linoleic acid will be converted to arachidonic acid (20 4, (o-6) by chain elongation and desaturation. As the three major families of unsaturated fatty acids (oleic acid, (o-9 linoleic acid, cu-6 and linolenic acid, cu-3) (Table 3) are metabolically nearly inconvertible in mammalians, phytoplankton and algae, which synthesize eicosapentaenoic acid (20 5, cu-3) and docosahexaenoic acid (22 6, cu-3), are the principal sources of the major cu-3 fatty acids. Only a-linolenic acid from vegetable oils is in principle able to be partially converted to eicosapentaenoic acid ([26] Fig. 2). 

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