Oleic acid is a
fatty acid that occurs naturally in various
animal and
vegetable fats and oils. It is an odorless, colorless oil, although commercial samples may be yellowish due to the presence of impurities. In chemical terms, oleic acid is classified as a
monounsaturatedomega-9 fatty acid, abbreviated with a
lipid number of 18:1
cis-9, and a main product of
Δ9-desaturase.[2] It has the formula CH3−(CH2)7−CH=CH−(CH2)7−COOH.[3][page needed] The name derives from the Latin word oleum, which means oil.[4] It is the most common fatty acid in nature.[5] The salts and esters of oleic acid are called oleates. It is a common component of oils, and thus occurs in many types of food, as well as in soap.
Occurrence
Fatty acids (or their salts) often do not occur as such in biological systems. Instead fatty acids such as oleic acid occur as their
esters, commonly
triglycerides, which are the greasy materials in many natural oils. Oleic acid is the most common monounsaturated fatty acid in nature. It is found in fats (triglycerides), the phospholipids that make membranes,
cholesterol esters, and
wax esters.[6]
Oleic acid undergoes the typical reactions of carboxylic acids and
alkenes. It is soluble in
aqueous base to give
soaps called oleates. Iodine adds across the double bond. Hydrogenation of the double bond yields the
saturated derivative
stearic acid.
Oxidation at the
double bond occurs slowly in air, and is known as
rancidification in foodstuffs and as
drying in coatings.
The
trans isomer of oleic acid is called
elaidic acid or trans-9-octadecenoic acid. These isomers have distinct physical properties and biochemical properties. Elaidic acid, the most abundant trans fatty acid in diet, appears to have an adverse effect on health.[17] A reaction that converts oleic acid to elaidic acid is called
elaidinization.
Another naturally occurring isomer of oleic acid is
petroselinic acid.
In chemical analysis, fatty acids are separated by gas chromatography of their methyl ester derivatives. Alternatively, separation of unsaturated isomers is possible by
argentation thin-layer chromatography.[18]
Oleic acid is used as a component in many foods, in the form of its triglycerides. It is a component of the normal human diet, being a part of animal fats and vegetable oils.
Oleic acid as its sodium salt is a major component of soap as an
emulsifying agent. It is also used as an
emollient.[51] Small amounts of oleic acid are used as an
excipient in pharmaceuticals, and it is used as an emulsifying or solubilizing agent in aerosol products.[52]
E.O. Wilson found that oleic acid is used by ants; when a dead ant's corpse begins to emit oleic acid, other ants in the
colony transport it away to the ant refuse pile.[53][54][55][56]
Niche uses
Oleic acid is used to induce lung damage in certain types of animals for the purpose of testing new drugs and other means to treat lung diseases. Specifically in sheep, intravenous administration of oleic acid causes acute lung injury with corresponding
pulmonary edema.[57]
Oleic acid is used as a soldering flux in stained glass work for joining
lead came.[58]
Health effects
Oleic acid is the most common
monounsaturated fat in the human diet (~90% of all monounsaturated fats).[59] Monounsaturated fat consumption has been associated with decreased
low-density lipoprotein (LDL) cholesterol, and possibly with increased
high-density lipoprotein (HDL) cholesterol.[60] Oleic acid may be responsible for the
hypotensive (
blood pressure reducing) effects of
olive oil that is considered a health benefit.[61] A 2017 review found that diets enriched in oleic acid are beneficial for regulating body weight.[62]
The United States
FDA has approved a health claim on reduced risk of coronary heart disease for high oleic (> 70% oleic acid) oils.[63] Some oil plants have cultivars bred to increase the amount of oleic acid in the oils. In addition to providing a health claim, the heat stability and shelf life may also be improved, but only if the increase in monounsaturated oleic acid levels correspond to a substantial reduction in polyunsaturated fatty acid (especially
α-linolenic acid) content.[64] When the saturated fat or trans fat in a
fried food is replaced with a stable high oleic oil, consumers may be able to avoid certain
health risks associated with consuming saturated fat and
trans fat.[65][66]
^Villarreal-Lozoya, Jose E.; Lombardini, Leonardo; Cisneros-Zevallos, Luis (2007). "Phytochemical constituents and antioxidant capacity of different pecan Carya illinoinensis (Wangenh.) K. Koch cultivars". Food Chemistry. 102 (4): 1241–1249.
doi:
10.1016/j.foodchem.2006.07.024.
^Moore, K. M.; Knauft, D. A. (1989). "The Inheritance of High Oleic Acid in Peanut". The Journal of Heredity. 80 (3): 252–3.
doi:
10.1093/oxfordjournals.jhered.a110845.
^Nutter, Mary K.; Lockhart, Ernest E.; Harris, Robert S. (1943). "The chemical composition of depot fats in chickens and turkeys". Oil & Soap. 20 (11): 231–4.
doi:
10.1007/BF02630880.
S2CID84893770.
^Kokatnur, MG; Oalmann, MC; Johnson, WD; Malcom, GT; Strong, JP (1979). "Fatty acid composition of human adipose tissue from two anatomical sites in a biracial community". The American Journal of Clinical Nutrition. 32 (11): 2198–205.
doi:
10.1093/ajcn/32.11.2198.
PMID495536.
^Toledo Hijo, Ariel A. C.; Maximo, Guilherme J.; Costa, Mariana C.; Cunha, Rosiane L.; Pereira, Jorge F. B.; Kurnia, Kiki A.; Batista, Eduardo A. C.; Meirelles, Antonio J. A. (2017). "Phase Behavior and Physical Properties of New Biobased Ionic Liquid Crystals". The Journal of Physical Chemistry B. 121 (14): 3177–3189.
doi:
10.1021/acs.jpcb.7b01384.
PMID28332847.
^Breuer, B.; Fock, H. P. (1987). "Separation of fatty acids or methyl esters including positional and geometric isomers by alumina argentation thin-layer chromatography". J. Chromatogr. Sci. 25 (7): 302–306.
doi:
10.1093/chromsci/25.7.302.
PMID3611285.
^Marinescu, Smaranda C.; Schrock, Richard R.; Müller, Peter; Hoveyda, Amir H. (2009). "Ethenolysis Reactions Catalyzed by Imido Alkylidene Monoaryloxide Monopyrrolide (MAP) Complexes of Molybdenum". J. Am. Chem. Soc. 131 (31): 10840–10841.
doi:
10.1021/ja904786y.
PMID19618951.
^
abc"US National Nutrient Database, Release 28". United States Department of Agriculture. May 2016. All values in this table are from this database unless otherwise cited or when italicized as the simple arithmetic sum of other component columns.
^"Avocado oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
^"Brazil nut oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
^"Canola oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
^"Coconut oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
^Callaway J, Schwab U, Harvima I, Halonen P, Mykkänen O, Hyvönen P, Järvinen T (April 2005). "Efficacy of dietary hempseed oil in patients with atopic dermatitis". The Journal of Dermatological Treatment. 16 (2): 87–94.
doi:
10.1080/09546630510035832.
PMID16019622.
S2CID18445488.
^"Palm oil, fat composition, 100 g". US National Nutrient Database, Release 28, United States Department of Agriculture. May 2016. Retrieved 6 September 2017.
^Orthoefer FT (2005). "Chapter 10: Rice Bran Oil". In Shahidi F (ed.). Bailey's Industrial Oil and Fat Products. Vol. 2 (6th ed.). John Wiley & Sons, Inc. p. 465.
doi:
10.1002/047167849X.
ISBN978-0-471-38552-3.
^Aladedunye, Felix; Przybylski, Roman (December 2013). "Frying stability of high oleic sunflower oils as affected by composition of tocopherol isomers and linoleic acid content". Food Chemistry. 141 (3): 2373–2378.
doi:
10.1016/j.foodchem.2013.05.061.
PMID23870970.