Linoleic acid

Source: Wikipedia, the free encyclopedia.
Not to be confused with
alpha-linolenic acid, lipoic acid, or linolelaidic acid
.

Linoleic acid
Names
Preferred IUPAC name
(9Z,12Z)-Octadeca-9,12-dienoic acid
Other names
cis,cis-9,12-Octadecadienoic acid
C18:2 (Lipid numbers)
Identifiers
3D model (
JSmol
)
3DMet
1727101
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard
 100.000.428 Edit this at Wikidata
EC Number
  • 200-470-9
57557
IUPHAR/BPS
KEGG
UNII
  • InChI=1S/C18H32O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20/h6-7,9-10H,2-5,8,11-17H2,1H3,(H,19,20)/b7-6-,10-9- checkY
    Key: OYHQOLUKZRVURQ-HZJYTTRNSA-N checkY
  • InChI=1/C18H32O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20/h6-7,9-10H,2-5,8,11-17H2,1H3,(H,19,20)/b7-6-,10-9-
    Key: OYHQOLUKZRVURQ-HZJYTTRNBX
  • CCCCC/C=C\C/C=C\CCCCCCCC(=O)O
Properties
C18H32O2
Molar mass 280.452 g·mol−1
Appearance Colorless oil
Density 0.9 g/cm3[1]
Melting point −12 °C (10 °F)[1]
−6.9 °C (19.6 °F)[2]
−5 °C (23 °F)[3]
Boiling point 229 °C (444 °F) at 16 mmHg[2]
230 °C (446 °F) at 21 mbar[3]
230 °C (446 °F) at 16 mmHg[1]
0.139 mg/L[3]
Vapor pressure 16 Torr at 229 °C[citation needed]
Acidity (pKa) 4.77 at 25°C[4]
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
1
0
Flash point 112 °C (234 °F)[3]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Linoleic acid (LA) is an

cis. It is a fatty acid sometimes denoted 18:2 (n-6) or 18:2 cis-9,12. A linoleate is a salt or ester of this acid.[5]

Linoleic acid is a

free fatty acid.[6] It is one of two essential fatty acids for humans, who must obtain it through their diet,[7]
and the most essential, because the body uses it as a base to make the others.

The word "linoleic" derives from

Latin linum 'flax', and oleum 'oil', reflecting the fact that it was first isolated from linseed oil
.

History

In 1844,

T.P. Hilditch and others in 1939, and it was synthesized by R. A. Raphael and F. Sondheimer in 1950.[12]

In physiology

Main articles: Fatty acid desaturase and Fatty acid synthesis

The consumption of linoleic acid is vital to proper health, as it is an essential fatty acid.[13]

Metabolism and eicosanoids

Linoleic acid (LA: C
18H
32O
2; 18:2, ω-6) is a precursor to arachidonic acid (AA: C
20H
32O
2; 20:4, ω-6) with elongation and unsaturation.[13] AA is the precursor to some prostaglandins,[14] leukotrienes (LTA, LTB, LTC), thromboxane (TXA)[15] and the N-acylethanolamine (NAE) arachidonoylethanolamine (AEA: C
22H
37NO
2; 20:4, ω-6),[16] and other endocannabinoids and eicosanoids.[17]

The metabolism of LA to AA begins with the conversion of LA into gamma-linolenic acid (GLA), effected by Δ6-desaturase.[18] GLA is converted to dihomo-γ-linolenic acid (DGLA), the immediate precursor to AA.

LA is also converted by various lipoxygenases, cyclooxygenases, cytochrome P450 enzymes (the CYP monooxygenases), and non-enzymatic autoxidation mechanisms to mono-hydroxyl products viz., 13-Hydroxyoctadecadienoic acid, and 9-Hydroxyoctadecadienoic acid; these two hydroxy metabolites are enzymatically oxidized to their keto metabolites, 13-oxo-octadecadienoic acid and 9-oxo-octadecdienoic acid. Certain cytochrome P450 enzymes, the CYP epoxygenases, catalyze oxidation of LA to epoxide products viz., its 12,13-epoxide, vernolic acid, and its 9,10-epoxide, coronaric acid. These linoleic acid products are implicated in human physiology and pathology.[19]

FAAH, the enzyme that breaks down AEA and other endocannabinoids, and the compound linoleoyl-ethanol-amide (C
20H
37NO
2; 18:2,n-6), an N-acylethanolamine,[clarification needed] - the ethanolamide of linoleic acid (LA: C
18H
32O
2; 18:2, n-6) and its metabolized incorporated ethanolamine (MEA: C
2H
7NO),[20] is the first natural inhibitor of FAAH, discovered.[21][22]

Uses and reactions

Linoleic acid is a component of quick-

allylic C−H groups (−CH=CH−CH2−CH=CH−) toward oxygen in air (autoxidation). Addition of oxygen leads to crosslinking and formation of a stable film.[23]

Reduction of the carboxylic acid group of linoleic acid yields linoleyl alcohol.[24]

Linoleic acid is a surfactant with a critical micelle concentration of 1.5 x 10−4 M @ pH 7.5.[citation needed]

Linoleic acid has become increasingly popular in the beauty products industry because of its beneficial properties on the skin. Research points to linoleic acid's anti-inflammatory, acne reductive, skin-lightening and moisture retentive properties when applied topically on the skin.[25][26][27][28]

Linoleic acid is also used in some bar of soap products.

Dietary sources

See also: Vegetable oil § Composition of fats

It is abundant in

almonds.[29][30]

Name % LA† ref.
Salicornia oil 75%
Safflower oil 72-78% [31]
Evening Primrose oil 65-80% [32]
Melon seed
oil		 70%
Poppyseed oil 70%
Grape seed oil 69.6%
Prickly Pear seed oil 63%
Artichoke oil 60%
Hemp oil 54.3% [33]
Wheat germ oil 55%
Cottonseed oil 54%
Corn oil 51.9% [34]
Walnut oil 51%
Soybean oil 50.9% [35]
Sesame oil 45%
Pumpkin seed oil 42-59% [36]
Rice bran oil 39%
Argan oil 37%
Pistachio oil 32.7%
Peach oil 29% [37]
Almonds 24%
Canola
oil		 17.8% [38]
Sunflower oil 20.5% [39]
Chicken fat 18-23% [40]
Peanut oil 19.6% [41]
Egg yolk 16%
Linseed oil (flax), cold pressed 14.2% [42]
Lard 10%
Palm oil 10%
Olive oil 8.4% [43]
Cocoa butter 3%
Macadamia oil 2%
Butter 2%
Coconut oil 2%
  †average val

Other occurrences

Cockroaches release oleic and linoleic acid upon death, which discourages other roaches from entering the area. This is similar to the mechanism found in ants and bees, which release oleic acid upon death.[44]

Health effects

Consumption of linoleic acid has been associated with lowering the risk of cardiovascular disease, diabetes and premature death.[45][46][47] There is high-quality evidence that increased intake of linoleic acid decreases total blood cholesterol and low-density lipoprotein.[48]

The American Heart Association advises people to replace saturated fat with linoleic acid to reduce CVD risk.[49]

See also

References

  1. ^ a b c The Merck Index, 11th Edition, 5382
  2. ^
    ISBN 978-1-4987-5429-3
    .
  3. ^ a b c d Record of CAS RN 60-33-3 in the GESTIS Substance Database of the Institute for Occupational Safety and Health
  4. ^ National Center for Biotechnology Information (2024). PubChem Compound Summary for CID 5280450, Linoleic Acid. Retrieved January 20, 2024 from https://pubchem.ncbi.nlm.nih.gov/compound/Linoleic-Acid.
  5. ^ "Fatty Acids". Cyber Lipid. Archived from the original on 28 October 2018. Retrieved 31 July 2017.
  6. PMID 19400700
    .
  7. S2CID 9044197
    .
  8. ^ F. Sacc (1844) "Ueber das Leinöl, seine physicalischen und chemischen Eigenscharften und seine Oxydationsproducte". Liebig Annalen, volume 51, pages 213-230.
  9. ^ F. Sacc (1845): "Expériences sur les propriétés physiques et chimiques de l'huile de Lin". SChweizer. Gesell. N. Dekschr., volume 7
  10. ^ (1886), Monatsch., volume 7, pages 522-
  11. ^ (1930: J Biol Chem, volume 86, pages 587-
  12. doi:10.1039/jr9500002100
  13. ^
    PMID 23674797
    .
  14. PMID 4723909
    .
  15. PMID 6326200
    .
  16. PMID 33671938
    .
  17. PMID 32121018
    .
  18. PMID 8386433
    .
  19. PMID 28531128
    .
  20. ^ PubChem. "Linoleoyl ethanolamide". pubchem.ncbi.nlm.nih.gov. Retrieved 29 October 2022.
  21. PMID 9822713
    .
  22. PMID 29789479
    .
  23. ISBN 978-3527306732
    .
  24. doi:10.15227/orgsyn.029.0080
    .
  25. ^ Diezel, W.E.; Schulz, E.; Skanks, M.; Heise, H. (1993). "Plant oils: Topical application and anti-inflammatory effects (croton oil test)". Dermatologische Monatsschrift. 179: 173.
  26. S2CID 28594076
    .
  27. S2CID 23036319
    .
  28. PMID 12113324
    .
  29. ^ "Nutrient Data Laboratory Home Page". USDA National Nutrient Database for Standard Reference, Release 20. U.S. Department of Agriculture, Agricultural Research Service. 2007. Archived from the original on 14 April 2016.
  30. PMID 25328170
    .
  31. ISBN 978-0-12-394786-4
    .
  32. ^ "Evening Primrose Oil for Menopause does it help". 26 January 2018.
  33. doi:10.1016/S0308-8146(01)00245-X
    .
  34. ^ "FoodData Central". fdc.nal.usda.gov.
  35. ^ "FoodData Central". fdc.nal.usda.gov.
  36. PMID 23561092.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  37. doi:10.1016/j.lwt.2011.05.012
    .
  38. ^ "FoodData Central". fdc.nal.usda.gov.
  39. ^ "FoodData Central". fdc.nal.usda.gov.
  40. S2CID 84893770
    .
  41. ^ "FoodData Central". fdc.nal.usda.gov.
  42. ^ "FoodData Central". fdc.nal.usda.gov.
  43. ^ "FoodData Central". fdc.nal.usda.gov.
  44. ^ "Earth News: Ancient 'smell of death' revealed". BBC. 9 September 2009.
  45. PMID 32020162
    .
  46. S2CID 208516015
    .
  47. S2CID 237255109
    .
  48. ^ "Systematic review of the evidence for relationships between saturated, cis monounsaturated, cis polyunsaturated fatty acids and selected individual fatty acids, and blood cholesterol concentration". foodstandards.gov.au. Retrieved 10 January 2023.
  49. S2CID 367602
    .

Further reading

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Linoleic_acid&oldid=1199907413"