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Polyunsaturated fatty acid

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Polyunsaturated fatty acids are fatty acids that contain more than one double bond

Double bond

A double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that between two carbon atoms, can be found in alkenes. Many types of double bonds between two different elements exist, for example in...

in their backbone. This class includes many important compounds, such as essential fatty acid

Essential fatty acid

Essential fatty acids, or EFAs, are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them...

s and those that give drying oil

Drying oil

A drying oil is an oil that hardens to a tough, solid film after a period of exposure to air. The oil hardens through a chemical reaction in which the components crosslink by the action of oxygen . Drying oils are a key component of oil paint and some varnishes...

s their characteristic property.

Polyunsaturated fatty acids can be classified in various groups by their chemical structure:

Methylene-Interrupted Polyenes

These fatty acids have 2 or more cis double bonds that are separated from each other by a single methylene

Methylene

Methylene is a chemical species in which a carbon atom is bonded to two hydrogen atoms. Three different possibilities present themselves:* the -CH2- substituent group: e.g., dichloromethane ....

group. (This form is also sometimes called a divinylmethane pattern.)

Methylene- interrupted double bonds
-C-C=C-C-C=C-

The essential fatty acids are all omega-3 and -6 methylene-interrupted fatty acids. See more at Essential fatty acids—Nomenclature

Omega-3

align=center| Omega-3 fatty acid
Omega-3 fatty acid
N−3 fatty acids are essential unsaturated fatty acids with a double bond starting after the third carbon atom from the end of the carbon chain....

s
Common name	Lipid name	Chemical name
Hexadecatrienoic acid (HTA)	16:3 (n-3)	all-cis 7,10,13-hexadecatrienoic acid
Alpha-linolenic acid Alpha-linolenic acid α-Linolenic acid is an organic compound found in many common vegetable oils. In terms of its structure, it is named all-cis-9,12,15-octadecatrienoic acid. In physiological literature, it is given the name 18:3 .... (ALA)	18:3 (n-3)	all-cis-9,12,15-octadecatrienoic acid
Stearidonic acid Stearidonic acid Stearidonic acid is an ω-3 fatty acid, sometimes called moroctic acid. It is biosynthesized from alpha-linolenic acid by the enzyme delta-6-desaturase. Natural sources of this fatty acid are the seed oils of hemp, blackcurrant, corn gromwell and echium, and the cyanobacterium Spirulina.... (SDA)	18:4 (n-3)	all-cis-6,9,12,15,-octadecatetraenoic acid
Eicosatrienoic acid (ETE)	20:3 (n-3)	all-cis-11,14,17-eicosatrienoic acid
Eicosatetraenoic acid Eicosatetraenoic acid Eicosatetraenoic acid, ETA, designates any straight chain 20:4 fatty acid.Two isomers, both of them essential fatty acids, are of particular interest:* all-cis 5,8,11,14-eicosatetraenoic acid is an ω-6 fatty acid with the trivial name arachidonic acid... (ETA)	20:4 (n-3)	all-cis-8,11,14,17-eicosatetraenoic acid
Eicosapentaenoic acid Eicosapentaenoic acid Eicosapentaenoic acid is an omega-3 fatty acid. In physiological literature, it is given the name 20:5. It also has the trivial name timnodonic acid... (EPA, Timnodonic acid)	20:5 (n-3)	all-cis-5,8,11,14,17-eicosapentaenoic acid
Heneicosapentaenoic acid (HPA)	21:5 (n-3)	all-cis-6,9,12,15,18-heneicosapentaenoic acid
Docosapentaenoic acid Docosapentaenoic acid Docosapentaenoic acid designates any straight chain 22:5 fatty acid.Two isomers are of particular interest* all-cis-7,10,13,16,19-docosapentaenoic acid is an ω-3 fatty acid with the trivial name clupanodonic acid, commonly called DPA. It is an intermediary between eicosapentaenoic acid and... (DPA, Clupanodonic acid)	22:5 (n-3)	all-cis-7,10,13,16,19-docosapentaenoic acid
Docosahexaenoic acid Docosahexaenoic acid Docosahexaenoic acid is an omega-3 fatty acid that is a primary structural component of the human brain and retina. In chemical structure, DHA is a carboxylic acid with a 22-carbon chain and six cis double bonds; the first double bond is located at the third carbon from the omega end... (DHA, Cervonic acid)	22:6 (n-3)	all-cis-4,7,10,13,16,19-docosahexaenoic acid
Tetracosapentaenoic acid	24:5 (n-3)	all-cis-9,12,15,18,21-tetracosapentaenoic acid
Tetracosahexaenoic acid (Nisinic acid)	24:6 (n-3)	all-cis-6,9,12,15,18,21-tetracosahexaenoic acid

Omega-6

align=center|Omega-6 fatty acid
Omega-6 fatty acid
n−6 fatty acids are a family of unsaturated fatty acids that have in common a final carbon–carbon double bond in the n−6 position, that is, the sixth bond, counting from the methyl end.The biological effects of the n−6 fatty acids are largely mediated by their conversion to n-6 eicosanoids...

s
Common name	Lipid name	Chemical name
Linoleic acid Linoleic acid Linoleic acid is an unsaturated n-6 fatty acid. It is a colorless liquid at room temperature. In physiological literature, it has a lipid number of 18:2...	18:2 (n-6)	all-cis-9,12-octadecadienoic acid
Gamma-linolenic acid Gamma-Linolenic acid γ-Linolenic acid is a fatty acid found primarily in vegetable oils... (GLA)	18:3 (n-6)	all-cis-6,9,12-octadecatrienoic acid
Eicosadienoic acid	20:2 (n-6)	all-cis-11,14-eicosadienoic acid
Dihomo-gamma-linolenic acid Dihomo-gamma-linolenic acid Dihomo-γ-linolenic acid is a 20-carbon ω−6 fatty acid. In physiological literature, it is given the name 20:3 . DGLA is a carboxylic acid with a 20-carbon chain and three cis double bonds; the first double bond is located at the sixth carbon from the omega end. DGLA is the elongation product... (DGLA)	20:3 (n-6)	all-cis-8,11,14-eicosatrienoic acid
Arachidonic acid Arachidonic acid Arachidonic acid is a polyunsaturated omega-6 fatty acid 20:4.It is the counterpart to the saturated arachidic acid found in peanut oil, Arachidonic acid (AA, sometimes ARA) is a polyunsaturated omega-6 fatty acid 20:4(ω-6).It is the counterpart to the saturated arachidic acid found in peanut oil,... (AA)	20:4 (n-6)	all-cis-5,8,11,14-eicosatetraenoic acid
Docosadienoic acid	22:2 (n-6)	all-cis-13,16-docosadienoic acid
Adrenic acid Docosatetraenoic acid Docosatetraenoic acid designates any straight chain 22:4 fatty acid. One isomer is of particular interest:...	22:4 (n-6)	all-cis-7,10,13,16-docosatetraenoic acid
Docosapentaenoic acid Docosapentaenoic acid Docosapentaenoic acid designates any straight chain 22:5 fatty acid.Two isomers are of particular interest* all-cis-7,10,13,16,19-docosapentaenoic acid is an ω-3 fatty acid with the trivial name clupanodonic acid, commonly called DPA. It is an intermediary between eicosapentaenoic acid and... (Osbond acid)	22:5 (n-6)	all-cis-4,7,10,13,16-docosapentaenoic acid
Tetracosatetraenoic acid	24:4 (n-6)	all-cis-9,12,15,18-tetracosatetraenoic acid
Tetracosapentaenoic acid	24:5 (n-6)	all-cis-6,9,12,15,18-tetracosapentaenoic acid

Omega-9

align=center|Omega-9 fatty acid
Omega-9 fatty acid
n−9 fatty acids are a family of unsaturated fatty acids which have in common a final carbon–carbon double bond in the n−9 position; that is, the ninth bond from the end of the fatty acid.-Background:Some n−9s are common components of animal fat and vegetable oil...

s, mono- and polyunsaturated
Common name	Lipid name	Chemical name
Oleic acid Oleic acid Oleic acid is a monounsaturated omega-9 fatty acid found in various animal and vegetable fats. It has the formula CH37CH=CH7COOH. It is an odorless, colourless oil, although commercial samples may be yellowish. The trans isomer of oleic acid is called elaidic acid... ^†	18:1 (n-9)	cis-9-octadecenoic acid
Eicosenoic acid Eicosenoic acid Eicosenoic acid is a monounsaturated omega-9 fatty acid found in a variety of plant oils.... ^†	20:1 (n-9)	cis-11-eicosenoic acid
Mead acid Mead acid Mead acid is an omega-9 fatty acid, first characterized by James F. Mead. Like some other omega-9 polyunsaturated fatty acids animals can make Mead acid de novo. Its elevated presence in the blood is an indication of essential fatty acid deficiency...	20:3 (n-9)	all-cis-5,8,11-eicosatrienoic acid
Erucic acid Erucic acid Erucic acid is a monounsaturated omega-9 fatty acid, denoted 22:1 ω-9. It has the formula CH37CH=CH11COOH. It is prevalent in rapeseed, wallflower seed, and mustard seed, making up 40-50% of their oils... ^†	22:1 (n-9)	cis-13-docosenoic acid
Nervonic acid Nervonic acid Nervonic acid is a monounsaturated omega-9 fatty acid. Nervonic acid has been identified as important in the biosynthesis of nerve cell myelin... ^†	24:1 (n-9)	cis-15-tetracosenoic acid
^†Monounsaturated Monounsaturated fat In biochemistry and nutrition, monounsaturated fats or MUFA are fatty acids that have one double bond in the fatty acid chain and all of the remainder of the carbon atoms in the chain are single-bonded...

Conjugated fatty acids

Conjugated double bonds
-C=C-C=C-

align=center|Conjugated fatty acid
Conjugated fatty acid
Conjugated fatty acids are polyunsaturated fatty acids in which at least one pair of double bonds are separated by only one single bond, as in conjugated linoleic acid:The conjugation results in delocalization of electrons along the system.-See also:...

s have two or more conjugated double bonds
Conjugated system
In chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in compounds with alternating single and multiple bonds, which in general may lower the overall energy of the molecule and increase stability. Lone pairs, radicals or carbenium ions may be part of the...
Common name	Lipid name	Chemical name
Conjugated Linoleic Acid Conjugated linoleic acid Conjugated linoleic acids are a family of at least 28 isomers of linoleic acid found mainly in the meat and dairy products derived from ruminants. As the name implies, the double bonds of CLAs are conjugated, with only one single bond between them.... s (two conjugated double bonds)
Rumenic acid Rumenic acid Rumenic acid, also known as bovinic acid, is a conjugated linoleic acid found in the fat of ruminants and in dairy products. It is an omega-7 trans fat. Its lipid shorthand name is cis-9, trans-11 18:2 acid....	18:2 (n-7)	9Z,11E-octadeca-9,11-dienoic acid
	18:2 (n-6)	10E,12Z-octadeca-9,11-dienoic acid
Conjugated Linolenic Acids (three conjugated double bonds)
α-Calendic acid Calendic acid Calendic acid is an unsaturated fatty acid, named for the pot marigold , from which it is obtained. It is chemically similar to the conjugated linoleic acids; laboratory work suggests it may have similar health benefits.-Biosynthesis:Calendic acid is an omega-6 fatty acid...	18:3 (n-6)	8E,10E,12Z-octadecatrienoic acid
β-Calendic acid Calendic acid Calendic acid is an unsaturated fatty acid, named for the pot marigold , from which it is obtained. It is chemically similar to the conjugated linoleic acids; laboratory work suggests it may have similar health benefits.-Biosynthesis:Calendic acid is an omega-6 fatty acid...	18:3 (n-6)	8E,10E,12E-octadecatrienoic acid
Jacaric acid Jacaric acid Jacaric acid is a conjugated polyunsaturated fatty acid. The melting point of this fatty acid is 44 °C. It occurs naturally in the seeds of the Jacaranda mimosifolia which contain about 36% jacaric acid....	18:3 (n-6)	8E,10Z,12E-octadecatrienoic acid
α-Eleostearic acid	18:3 (n-5)	9Z,11E,13E-octadeca-9,11,13-trienoic acid
β-Eleostearic acid Beta-Eleostearic acid β-Eleostearic acid, or -octadeca-9,11,13-trienoic acid, is an organic compound with formula or H3C-33-7-OH. It is the all-trans conformational isomer of octadecatrienoic acid.-See also:...	18:3 (n-5)	9E,11E,13E-octadeca-9,11,13-trienoic acid
Catalpic acid Catalpic acid Catalpic acid is a conjugated polyunsaturated fatty acid. The melting point of this fatty acid is 32 °C. Catalpic acid occurs naturally in the seeds of Catalpa ovata and Southern Catalpa . Seeds of Catalpa species contain about 40% catalpic acid....	18:3 (n-5)	9Z,11Z,13E-octadeca-9,11,13-trienoic acid
Punicic acid Punicic acid Punicic acid is a polyunsaturated fatty acid, 18:3 . It is named for the pomegranate, , and is obtained from pomegranate seed oil....	18:3 (n-5)	9Z,11E,13Z-octadeca-9,11,13-trienoic acid
Other
Rumelenic acid	18:3 (n-3)	9E,11Z,15E-octadeca-9,11,15-trienoic acid
α-Parinaric acid	18:4 (n-3)	9E,11Z,13Z,15E-octadeca-9,11,13,15-trienoic acid
β-Parinaric acid	18:4 (n-3)	all trans-octadeca-9,11,13,15-trienoic acid
Bosseopentaenoic acid Bosseopentaenoic acid Bosseopentaenoic acid is a conjugated polyunsaturated fatty acid. Bosseopentaenoic acid can be extracted from the red coralline algae, Bossiella orbigniana....	20:5 (n-6)	5Z,8Z,10E,12E,14Z-eicosanoic acid

Other Polyunsaturates

Common name	Lipid name	Chemical name
Pinolenic acid Pinolenic acid Pinolenic acid is a fatty acid contained in the Korean Pine nut and the seeds of other conifers . The highest percentage of pinolenic acid is found in Siberian pine nuts and the oil produced by them....	18:3 (n-6)	(5Z,9Z,12Z)-octadeca-5,9,12-trienoic acid
Podocarpic acid	20:3 (n-6)	(5Z,11Z,14Z)-eicosa-5,11,14-trienoic acid

Function and effects

The biological effects of the ω-3 and ω-6 fatty acids are largely mediated by their mutual interactions, see Essential fatty acid interactions
Essential fatty acid interactions
The actions of the ω-3 and ω-6 essential fatty acids are best characterized by their interactions; they cannot be understood separately.Arachidonic acid is a 20-carbon ω-6 conditionally essential fatty acid...

for detail.