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Fatty acid
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Upper classes: LB LBF

(9Z,12Z) -Octadecadienoic acid
Structural Information
Systematic Name (cis-9,cis-12) -Octadecadienoic acid
Common Name
  • (9Z,12Z) -Octadecadienoic acid
  • Linoleic acid
Symbol LA / C18:2n-6 / C18:2 omega 6
Formula C18H32O2
Exact Mass 280.240230268
Average Mass 280.44548000000003
Physicochemical Information
Melting Point -5°C
Boiling Point 229°C to 230°C at 16mmHg
Density d20
Optical Rotation
Refractive Index 1.4711 at 20°C
Solubility soluble in acetone, alcohol, ether and petroleum ether. Matthews_NL et al. NicolaidesNet al.
Source Constituent of the essential fatty acids (vitamin F) and of various microorganisms; oils of cottonseed, soybean, peanut, corn, sunflower and poppy seed.
Chemical Synthesis
Metabolism Linoleic acid (18:2n-6) is synthesized from oleic acid (18:1n-9) by desaturation of Delta 12-desaturase, and alpha -linolenic acid (18:3n-3) is formed from linoleic acid by desaturation reaction of Delta 15-desaturase. Since both Delta 12- and 15-desaturases are present in plant cells but not in animal cells, linoleic and alpha -linolenic acid are not biosynthesized in animal cells in vivo. When ingested by animals, linoleic acid is desaturated, elongated to form gamma -linolenic acid (18:3n-6), dihomo- gamma -linolenic acid (20:3n-6), arachidonic acid (20:4n-6) and adrenic acid (22:4n-6). Docosapentaenoic acid (22:5n-6) is synthesized from adrenic acid in significant amounts only under conditions of prolonged n-3 fatty acid deficiency., No interconversion between the n-6 and n-3 series in mammals. Nutritionally, it is important to note that different foods contain different proportions of n-6/n-3 and therefore the n-6/n-3 ratio in tissue lipids change significantly depending on the choice of foods. Okuyama_H et al. Although plants synthesize and store linoleic acid and alpha -linolenic acid as well as saturated and monounsaturated fatty acids in grains, the proportions of these fatty acids in different vegetable oils differ greatly. Safflower and sunflower oil contain high levels of linoleate, while perilla and linseed oil are rich in alpha -linolenic acid.
Biological Activity There are two groups of essential fatty acids for mammals, the n-6 (or omega 6) and the n-3 (or omega 3). Linoleic acid (LA) is one of the n-6 essential fatty. Animals deficient in LA show the growth retardation, skin lesions, reproductive failure, fatty liver and polydipsia Paulsrud_JR et al.. Dietary supplementation of either linoleate, gamma -linoleate or arachidonate prevents such symptoms completely. Its physiological functions appear to be mediated mainly through the hormone-like eicosanoids (prostaglandins, leukotriens and thromboxanes et al.) derived from arachidonic acid which is biosynthesized from LA. LA is also shown to be involved in control of the water impermeability of the skin and regulation of cholesterol synthesis and transport.
Genetic Information
Spectral Information
Mass Spectra
UV Spectra
IR Spectra
NMR Spectra
Other Spectra
Chromatograms Gas liquid chromatogram
(provided by Dr. Akiko Horiuchi).
Reported Metabolites, References
Biospecies ID Compound Name Reference Comment
n.a. LBF18206SC05 See above. Matthews_NL et al. 1941
n.a. LBF18206SC05 See above. Nicolaides_N et al. 1958
n.a. LBF18206SC05 See above. Okuyama_H et al. 1996
n.a. LBF18206SC05 See above. Paulsrud_JR et al. 1972

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