Oleic acid is a fatty acid that occurs naturally in various

animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...

and

vegetable fats and oils Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or ...

. It is an odorless, colorless oil, although commercial samples may be yellowish. In chemical terms, oleic acid is classified as a

monounsaturated In nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such compounds, most commonly those that occur in living beings or in food. The term often refers specifically to triglycerides (triple est ...

omega-9 fatty acid Omega-9 fatty acids (ω−9 fatty acids or ''n''−9 fatty acids) are a family of unsaturated fatty acids which have in common a final carbon–carbon double bond in the omega−9 position; that is, the ninth bond from the methyl end of the fat ...

, abbreviated with a

lipid number In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, fr ...

of 18:1 ''cis''-9, and a main product of Δ9 desaturase. It has the formula CH₃(CH₂)₇CH=CH(CH₂)₇COOH. The name derives from the Latin word ''oleum'', which means oil. It is the most common fatty acid in nature. The salts and esters of oleic acid are called oleates.

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. Triglycerides of oleic acid comprise the majority of olive oil (about 70%). Olive oil exceeding 2% free oleic acid is graded unfit for human consumption. It also makes up 59–75% of

pecan oil Pecan oil is an edible pressed oil extracted from the pecan nut. Pecan oil is neutral in flavor and takes on the flavor of whatever seasoning is being used with it. Pecan oil contains 9.5% saturated fat, which is less than in olive oil (13.5%), p ...

, 61% of

canola Close-up of canola blooms Canola flower Rapeseed oil is one of the oldest known vegetable oils. There are both edible and industrial forms produced from rapeseed, the seed of several cultivars of the plant family Brassicaceae. Historically, ...

oil, 36–67% of peanut oil, 60% of

macadamia oil Macadamia oil (or macadamia nut oil) is the non-volatile oil collected from the nuts of the macadamia (''Macadamia integrifolia''), a native Australian plant. It is used in food as a frying or salad oil, and in cosmetic formulations as an emollien ...

, 20–80% of sunflower oil,(NDB ID: 04678, 04584) 15–20% of grape seed oil,

sea buckthorn oil Sea buckthorn oil is a red–orange oil derived from sea buckthorn plants. The most commonly used species for this purpose is '' Hippophae rhamnoides''. Species belonging to this genus accumulate lipids in the mesocarp (the fruit pulp), so th ...

, 40% of

sesame oil Sesame oil is an edible vegetable oil derived from sesame seeds. The oil is one of the earliest-known crop-based oils. Worldwide mass modern production is limited due to the inefficient manual harvesting process required to extract the oil. ...

, and 14% of

poppyseed oil Poppyseed oil (also poppy seed oil and poppy oil) is an edible oil obtained from poppy seeds (specifically seeds of ''Papaver somniferum'', the opium poppy). Poppy seeds yield 45–50% oil. Like poppy seeds, poppyseed oil is highly palatable, ...

. High oleic variants of plant sources such as sunflower (~80%) and canola oil (70%) also have been developed. Karuka contains 52.39% oleic acid. It is abundantly present in many animal fats, constituting 37 to 56% of chicken and turkey fat, and 44 to 47% of lard. Oleic acid is the most abundant fatty acid in human

adipose tissue Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular ...

, and second in abundance in human tissues overall, following palmitic acid.

Production and chemical behavior

The biosynthesis of oleic acid involves the action of the enzyme

stearoyl-CoA 9-desaturase Stearoyl-CoA desaturase (Δ-9-desaturase) is an endoplasmic reticulum enzyme that catalyzes the rate-limiting step in the formation of monounsaturated fatty acids (MUFAs), specifically oleate and palmitoleate from stearoyl-CoA and palmitoyl-CoA ...

acting on stearoyl-CoA. In effect, stearic acid is dehydrogenated to give the monounsaturated derivative, oleic acid. Oleic acid undergoes the reactions of carboxylic acids and alkenes. It is soluble in aqueous base to give

soap Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are use ...

s called oleates. Iodine adds across the double bond. Hydrogenation of the double bond yields the saturated derivative stearic acid.

Oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

at the

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betwee ...

occurs slowly in air, and is known as

rancidification Rancidification is the process of complete or incomplete autoxidation or hydrolysis of fats and oils when exposed to air, light, moisture, or bacterial action, producing short-chain aldehydes, ketones and free fatty acids. When these processes o ...

in foodstuffs and as drying in coatings. Reduction of the carboxylic acid group yields oleyl alcohol.

Ozonolysis In organic chemistry, ozonolysis is an organic reaction where the unsaturated bonds of alkenes (), alkynes (), or azo compounds () are cleaved with ozone (). Alkenes and alkynes form organic compounds in which the multiple carbon–carbon b ...

of oleic acid is an important route to azelaic acid. The coproduct is nonanoic acid: :H₁₇C₈CH=CHC₇H₁₄CO₂H + 4"O" → HO₂CC₇H₁₄CO₂H + H₁₇C₈CO₂H Esters of azelaic acid find applications in lubrications and plasticizer.

Related compounds

The

trans isomer Trans- is a Latin prefix meaning "across", "beyond", or "on the other side of". Used alone, trans may refer to: Arts, entertainment, and media * Trans (festival), a former festival in Belfast, Northern Ireland, United Kingdom * ''Trans'' (fil ...

of oleic acid is called

elaidic acid Elaidic acid is a chemical compound with the formula , specifically the fatty acid with structural formula HO(O=)C–(CH2–)7CH=CH–(CH2–)8H, with the double bond (between carbon atoms 9 and 10) in ''trans'' configuration. It is a colorle ...

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. A reaction that converts oleic acid to elaidic acid is called elaidinization. Another naturally occurring isomer of oleic acid is

petroselinic acid Petroselinic acid is a fatty acid that occurs naturally in several animal and vegetable fats and oils. It is a white powder and is commercially available. In chemical terms, petroselinic acid is classified as a monounsaturated omega-12 fatty ac ...

. 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. In ethenolysis, methyl oleate, the ''methyl ester'' of the acid, converts to

1-decene Decene is an organic compound with the chemical formula . Decene contains a chain of ten carbon atoms with one double bond, making it an alkene. There are many isomers of decene depending on the position and geometry of the double bond. Dec-1- ...

and methyl 9- decenoate: : CH₂=CH₂ → CH₃(CH₂)₇CH=CH₂ + MeO₂C(CH₂)₇CH=CH₂

Dietary sources

Uses

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. Small amounts of oleic acid are used as an

excipient An excipient is a substance formulated alongside the active ingredient of a medication, included for the purpose of long-term stabilization, bulking up solid formulations that contain potent active ingredients in small amounts (thus often referred ...

in pharmaceuticals, and it is used as an emulsifying or solubilizing agent in aerosol products.

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 Pulmonary edema, also known as pulmonary congestion, is excessive liquid accumulation in the tissue and air spaces (usually alveoli) of the lungs. It leads to impaired gas exchange and may cause hypoxemia and respiratory failure. It is due t ...

. Oleic acid is used as a soldering flux in stained glass work for joining lead came.

Nanoparticles

Oleic acid is widely used in the solution phase synthesis of

nanoparticle A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 10 ...

s, functioning as a to control the size and morphology of nanoparticles.

Health effects

Oleic acid is the topmost

monounsaturated fat Monounsaturated fats are fatty acids that have one double bond in the fatty acid chain with all of the remainder carbon atoms being single-bonded. By contrast, polyunsaturated fats have more than one double bond. Molecular description Fatty acid ...

in the human diet. Monounsaturated fat consumption has been associated with decreased low-density lipoprotein (LDL) cholesterol, and possibly with increased

high-density lipoprotein High-density lipoprotein (HDL) is one of the five major groups of lipoproteins. Lipoproteins are complex particles composed of multiple proteins which transport all fat molecules (lipids) around the body within the water outside cells. They are t ...

(HDL) cholesterol. Oleic acid may be responsible for the hypotensive ( blood pressure reducing) effects of olive oil that is considered a health benefit. A 2017 review found that diets enriched in oleic acid are beneficial for regulating body weight. The United States FDA has approved a health claim on reduced risk of coronary heart disease for high oleic (> 70% oleic acid) oils. 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 ''alpha''-Linolenic acid (ALA), also known as α-Linolenic acid (from Greek language, Greek ''alpha'' meaning "first" and ''linon'' meaning flax), is an omega-3 fatty acid, ''n''−3, or omega-3, essential fatty acid. ALA is found in many seeds ...

) content. 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 Trans fat, also called trans-unsaturated fatty acids, or trans fatty acids, is a type of unsaturated fat that naturally occurs in small amounts in meat and milk fat. It became widely produced as an unintentional byproduct in the industrial pr ...

References

External links

FATTY ACIDS: STRAIGHT-CHAIN MONOENOIC
(The AOCS Lipid Library)
9-octadecenoic acid
(NIST Chemistry Webbook) {{Authority control 5α-Reductase inhibitors Fatty acids Excipients Insect pheromones Insect ecology Insect repellents Alkenoic acids