Oleic acid is a

fatty acid In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an ...

that occurs naturally in various

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

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 monounsaturated omega-9 fatty acid, abbreviated with a lipid number of 18:1 ''cis''-9, and a main product of Δ9-desaturase. It has the formula . 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. 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

triglyceride A triglyceride (from '' tri-'' and '' glyceride''; also TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of body fat in humans and other vertebrates ...

s, 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, cholesteryl esters, and wax esters.

Triglyceride A triglyceride (from '' tri-'' and '' glyceride''; also TG, triacylglycerol, TAG, or triacylglyceride) is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of body fat in humans and other vertebrates ...

s of oleic acid comprise the majority of

olive oil Olive oil is a vegetable oil obtained by pressing whole olives (the fruit of ''Olea europaea'', a traditional Tree fruit, tree crop of the Mediterranean Basin) and extracting the oil. It is commonly used in cooking for frying foods, as a cond ...

(about 70%). It also makes up 59–75% of pecan oil, 61% of canola oil, 36–67% of peanut oil, 60% of macadamia oil, 20–80% of sunflower oil,(NDB ID: 04678, 04584) 15–20% of grape seed oil, sea buckthorn oil, 40% of sesame oil, and 14% of poppyseed oil. 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. Free oleic acid occurs in oils and fats as a product of the breakdown of triglycerides. Olive oil exceeding 2% free oleic acid is graded unfit for human consumption. See . It is a chemical signal use by some ants. Oleic acid is the most abundant fatty acid in human adipose tissue, and second in abundance in human tissues overall, following palmitic acid.

Production and chemical behavior

The

biosynthesis Biosynthesis, i.e., chemical synthesis occurring in biological contexts, is a term most often referring to multi-step, enzyme-Catalysis, catalyzed processes where chemical substances absorbed as nutrients (or previously converted through biosynthe ...

of oleic acid involves the action of the enzyme stearoyl-CoA 9-desaturase acting on stearoyl-CoA. In effect, stearic acid is dehydrogenated to give the monounsaturated derivative, oleic acid. Oleic acid undergoes the typical reactions of

carboxylic acids In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

and alkenes. It is soluble in aqueous base to give

soap Soap is a salt (chemistry), salt of a fatty acid (sometimes other carboxylic acids) used for cleaning and lubricating products as well as other applications. In a domestic setting, soaps, specifically "toilet soaps", are surfactants usually u ...

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

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

at the double bond occurs slowly in air, and is known as rancidification in foodstuffs and as drying in coatings. Reduction of the carboxylic acid group yields oleyl alcohol. Ozonolysis of oleic acid is an important route to azelaic acid. The coproduct is nonanoic acid: : Esters of azelaic acid find applications in lubrication and plasticizers. Neutralizing oleic acid with ethanolamines gives the protic ionic liquid monoethanolamine oleate.

Related compounds

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. 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. In ethenolysis, methyl oleate, the ''methyl ester'' of the acid, converts to 1-decene and methyl 9- decenoate: : Several

organometallic Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...

oleates exist: * Cobalt oleate * Copper oleate

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

Health effects

Oleic acid is the most common monounsaturated fat in the human diet (~90% of all monounsaturated fats). Monounsaturated fat consumption has been associated with decreased low-density lipoprotein (LDL) cholesterol, and possibly with increased high-density lipoprotein (HDL) cholesterol. Oleic acid may be responsible for the hypotensive (

blood pressure Blood pressure (BP) is the pressure of Circulatory system, circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term ...

reducing) effects of

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) 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.

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 Wood extracts