Linoleic acid (LA) is an
organic compound with the formula HOOC(CH2)7CH=CHCH2CH=CH(CH2)4CH3. Both
alkene groups (−CH=CH−) are
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]
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,
F. Sacc, working at the laboratory of
Justus von Liebig, isolated linoleic acid from linseed oil.[8][9] In 1886,
K. Peters determined the existence of two double bonds.[10] Its essential role in human diet was discovered by
G. O. Burr and others in 1930.[11] Its chemical structure was determined by
T.P. Hilditch and others in 1939, and it was synthesized by R. A. Raphael and F. Sondheimer in 1950.[12]
Linoleic acid is a component of quick-
drying oils, which are useful in
oil paints and
varnishes. These applications exploit the lability of the doubly
allylicC−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.
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]
^Simopoulos, Artemis P. (2008). "The importance of the omega-6/omega-3 fatty acid ratio in cardiovascular disease and other chronic diseases". Experimental Biology and Medicine. 233 (6): 674–688.
doi:
10.3181/0711-mr-311.
PMID18408140.
S2CID9044197.
^F. Sacc (1844) "Ueber das Leinöl, seine physicalischen und chemischen Eigenscharften und seine Oxydationsproducte". Liebig Annalen, volume 51, pages 213-230.
^R. A. Raphael and Franz Sondheimer (1950): "The synthesis of long-chain aliphatic acids from acetylenic compounds. Part III. The synthesis of linoleic acid". Journal of the Chemical Society (Resumed), article 432,
doi:
10.1039/jr9500002100
^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.
^Letawe, C.; Boone, M.; Pierard, G.E. (March 1998). "Digital image analysis of the effect of topically applied linoleic acid on acne microcomedones". Clinical and Experimental Dermatology. 23 (2): 56–58.
doi:
10.1046/j.1365-2230.1998.00315.x.
PMID9692305.
S2CID28594076.
^Ando, Hideya; Ryu, Atsuko; Hashimoto, Akira; Oka, Masahiro; Ichihashi, Masamitsu (March 1998). "Linoleic acid and α-linolenic acid lightens ultraviolet-induced hyperpigmentation of the skin". Archives of Dermatological Research. 290 (7): 375–381.
doi:
10.1007/s004030050320.
PMID9749992.
S2CID23036319.
^Darmstadt, Gary L.; Mao-Qiang, M.; Chi, E.; Saha, S.K.; Ziboh, V.A.; Black, R.E.; Santosham, M.; Elias, P.M. (2002). "Impact of topical oils on the skin barrier: possible implications for neonatal health in developing countries". Acta Paediatrica. 91 (5): 546–554.
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PMID12113324.
^"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.
^Oomah, B. Dave; Busson, Muriel; Godfrey, David V; Drover, John C. G (1 January 2002). "Characteristics of hemp (Cannabis sativa L.) seed oil". Food Chemistry. 76 (1): 33–43.
doi:
10.1016/S0308-8146(01)00245-X.
^Nawirska-Olszańska A, Kita A, Biesiada A, Sokół-Łętowska A, Kucharska AZ. (2013). "Characteristics of antioxidant activity and composition of pumpkin seed oils in 12 cultivars". Food Chemistry. 139 (1–4): 155–161.
doi:
10.1016/j.foodchem.2013.02.009.
PMID23561092.{{
cite journal}}: CS1 maint: multiple names: authors list (
link)
^Wu, Hao; Shi, John; Xue, Sophia; Kakuda, Yukio; Wang, Dongfeng; Jiang, Yueming; Ye, Xingqian; Li, Yanjun; Subramanian, Jayasankar (2011). "Essential oil extracted from peach (Prunus persica) kernel and its physicochemical and antioxidant properties". LWT - Food Science and Technology. 44 (10): 2032–2039.
doi:
10.1016/j.lwt.2011.05.012.
^M. K. Nutter, E. E. Lockhart and R. S. Harris (1943). "The chemical composition of depot fats in chickens and turkeys". Journal of the American Oil Chemists' Society. 20 (11): 231–234.
doi:
10.1007/BF02630880.
S2CID84893770.