Linoleic acid

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The chemical strucuture of linoleic acid showing physiological numbering (red) and chemical numbering (blue) conventions.

Linoleic acid (LA) is an unsaturated omega-6 fatty acid with the molecular formula C₁₈H₃₂O₂. It is a colorless liquid. In physiological literature, it is given the name 18:2(n-6). Its systematic chemical name is cis, cis-9,12-octadecadienoic acid.^[1] Chemically, linoleic acid is a carboxylic acid with an 18-carbon chain and two cis double bonds; the first double bond is located at the sixth carbon from the omega end. The structural formula is CH₃-CH₂-CH₂-CH₂-CH₂-CH=CH-CH₂-CH=CH-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-CH₂-COOH. Linoleic acid has a molar mass of 280.44548(1724) g/mol.

The word linoleic comes from the Greek word linon (flax). Oleic means of, relating to, or derived from oil or of or relating to oleic acid.

Linoleic acid is a polyunsaturated fatty acid used in the biosynthesis of prostaglandins and cell membranes and in other natural oils. These oils include vegetable oil, especially sunflower oil.

To be fully utilised by the body, LA must be converted into gamma-linolenic acid, a reaction catalysed by the enzyme delta-6-desaturase (D6D).

Linoleic acid is used in making soaps, emulsifiers, and quick-drying oils. Reduction of linoleic acid yields linoleyl alcohol.

Linoleic acid is a member of the group of essential fatty acids called omega-6 fatty acids, so called because they are an essential dietary requirement for all mammals. The other group of essential fatty acids is the omega-3 fatty acids, for example Alpha-linolenic acid. Omega-6 deficiency symptoms include dry hair, hair loss, [[1]] and poor wound healing[[2]]. It is easy to meet the daily requirement for these fatty acids (even for people consuming low fat diets) and most people get plenty of omega-6 fatty acids in their diet by consuming approximately a tablespoon of polyunsaturated plant oils per day.

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[edit] References

Cunnane SC &Anderson MJ. (1997). Pure linoleate deficiency in the rat: influence on growth, accumulation of n-6 polyunsaturates, and [1-14C]linoleate oxidation. Journal of Lipid Research. 38(4):805-12.

Ruthig DJ & Meckling-Gill KA. (1999). Both (n-3) and (n-6) fatty acids stimulate wound healing in the rat intestinal epithelial cell line, IEC-6. Journal of Nutrition. 129(10):1791-8.