Linoleic acid

linoleiclinoleatelinoleic acid metabolismlinoleoyl6linoleic acids(9''Z'',12''Z'')-octadeca-9,12-dienoic acid(C 18 H 32 O 2 )-Omega 69,12-Octadecadienoic acid
Linoleic acid (LA) is a polyunsaturated omega-6 fatty acid and is one of two essential fatty acids for humans, who must obtain it through their diet.wikipedia
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Omega-6 fatty acid

omega-6omega-6 fatty acidsω-6
Linoleic acid (LA) is a polyunsaturated omega-6 fatty acid and is one of two essential fatty acids for humans, who must obtain it through their diet.
Linoleic acid (18:2, n−6), the shortest-chained omega-6 fatty acid is categorized as an essential fatty acid because the human body cannot synthesize it.

Essential fatty acid

essential fatty acidsessentialEssential fatty acid deficiency
Linoleic acid (LA) is a polyunsaturated omega-6 fatty acid and is one of two essential fatty acids for humans, who must obtain it through their diet.
Only two fatty acids are known to be essential for humans: alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid).

Polyunsaturated fatty acid

polyunsaturated fatty acidspolyunsaturatedPUFA
Linoleic acid (LA) is a polyunsaturated omega-6 fatty acid and is one of two essential fatty acids for humans, who must obtain it through their diet.

Fatty acid

fatty acidsfree fatty acidsfree fatty acid
Linoleic acid is a fatty acid. Linoleic acid is a polyunsaturated fatty acid used in the biosynthesis of arachidonic acid (AA) and thus some prostaglandins, leukotrienes (LTA, LTB, LTC), and thromboxane (TXA).
Two essential fatty acids are linoleic acid (LA) and alpha-linolenic acid (ALA).

Polyunsaturated fat

polyunsaturatedpolyunsaturated fatty acidspolyunsaturated fats
Linoleic acid is a polyunsaturated fatty acid used in the biosynthesis of arachidonic acid (AA) and thus some prostaglandins, leukotrienes (LTA, LTB, LTC), and thromboxane (TXA).
The illustration below shows the omega-6 fatty acid, linoleic acid.

Arachidonic acid

arachidonic acid metabolismarachidonatearachidonic
Linoleic acid is a polyunsaturated fatty acid used in the biosynthesis of arachidonic acid (AA) and thus some prostaglandins, leukotrienes (LTA, LTB, LTC), and thromboxane (TXA).
However, it does become essential if a deficiency in linoleic acid exists or if an inability to convert linoleic acid to arachidonic acid occurs.

Hemp

industrial hemphemp seedhemp rope
It is abundant in many nuts, fatty seeds (flax seeds, hemp seeds, poppy seeds, sesame seeds, etc.) and their derived vegetable oils; comprising over half (by weight) of poppy seed, safflower, sunflower, corn, and soybean oils.
About 73% of the energy in hempseed is in the form of fats and essential fatty acids, mainly polyunsaturated fatty acids, linoleic, oleic, and alpha-linolenic acids.

Sunflower oil

sunflowersunflower seed oilsunflowers
It is abundant in many nuts, fatty seeds (flax seeds, hemp seeds, poppy seeds, sesame seeds, etc.) and their derived vegetable oils; comprising over half (by weight) of poppy seed, safflower, sunflower, corn, and soybean oils.
Sunflower oil is primarily composed of linoleic acid, a polyunsaturated fat, and oleic acid, a monounsaturated fat.

Flax

linseedflaxseedLinum usitatissimum
It is abundant in many nuts, fatty seeds (flax seeds, hemp seeds, poppy seeds, sesame seeds, etc.) and their derived vegetable oils; comprising over half (by weight) of poppy seed, safflower, sunflower, corn, and soybean oils. The word "linoleic" derives from the Greek word linon (flax).
As a percentage of total fat, flaxseeds contain 54% omega-3 fatty acids (mostly ALA), 18% omega-9 fatty acids (oleic acid), and 6% omega-6 fatty acids (linoleic acid); the seeds contain 9% saturated fat, including 5% as palmitic acid.

9-Hydroxyoctadecadienoic acid

9-HODE9-hydroperoxy/hydroxyl-octadecadienoic acids
In addition, LA is converted by various lipoxygenases, cyclooxygenases, certain cytochrome P450 enzymes (the CYP monooxygenases), and non-enzymatic autoxidation mechanisms to mono-hydroxyl products viz., 13-Hydroxyoctadecadienoic acid and 9-Hydroxyoctadecadienoic acid; these two hydroxy metabolites are enzymatically oxidized to their keto metabolites, 13-oxo-octadecadienoic acid and 9-oxo-octadecdienoic acid.
9-Hydroxyoctadecadienoic acid (9-hydroxy-10(E),12(Z)-octadecadienoic acid or 9-HODE) has been used in the literature to designate either or both of two stereoisomer metabolites of the essential fatty acid, linoleic acid: 9(S)-hydroxy-10(E),12(Z)-octadecadienoic acid (9(S)-HODE) and 9(R)-hydroxy-10(E),12(Z)-octadecadienoic acid (9(R)-HODE); these two metabolites differ in having their hydroxy residues in the S or R configurations, respectively.

13-Hydroxyoctadecadienoic acid

13-HODE13-hydoxyperoxy/hydroxy-octadecadienoic
In addition, LA is converted by various lipoxygenases, cyclooxygenases, certain cytochrome P450 enzymes (the CYP monooxygenases), and non-enzymatic autoxidation mechanisms to mono-hydroxyl products viz., 13-Hydroxyoctadecadienoic acid and 9-Hydroxyoctadecadienoic acid; these two hydroxy metabolites are enzymatically oxidized to their keto metabolites, 13-oxo-octadecadienoic acid and 9-oxo-octadecdienoic acid.
15-lipoxygenase 1 (ALOX15), while best known for converting the 20 carbon polyunsaturated fatty acid, arachidonic acid, into a series of 15-hydroxylated arachidonic acid metabolites (see 15-hydroxyicosatetraenoic acid), actually prefers as its substrate the 18 carbon polyunsaturated fatty acid, linoleic acid, over arachidonic acid, converting it to 13-hydroperoxy-9Z,11E-octadecadienoic acid (13-HpODE).

Dihomo-γ-linolenic acid

Dihomo-gamma-linolenic acidDGLADGLA (20:3 ω-6)
GLA is converted to dihomo-γ-linolenic acid (DGLA), which in turn is converted to arachidonic acid (AA).
GLA, in turn, is a desaturation product (Delta 6 desaturase) of linoleic acid (18:2, ω−6).

Vernolic acid

Vernonia oil
Certain cytochrome P450 enzymes, the CYP epoxygenases, metabolize LA to epoxide products viz., its 12,13-epoxide, Vernolic acid and its 9,10-epoxide, Coronaric acid.
It is the cis epoxide derived from the C12–C13 alkene of linoleic acid and exists both the - and - optical isomers.

Coronaric acid

Certain cytochrome P450 enzymes, the CYP epoxygenases, metabolize LA to epoxide products viz., its 12,13-epoxide, Vernolic acid and its 9,10-epoxide, Coronaric acid.
Coronaric acid (isoleukotoxin) is a mono-unsaturated, epoxide derivative of the di-saturated fatty acid, linoleic acid (i.e. 9(Z),12(Z) octadecadienoic acid.

Soybean oil

soybeansoya oilsoy oil
It is abundant in many nuts, fatty seeds (flax seeds, hemp seeds, poppy seeds, sesame seeds, etc.) and their derived vegetable oils; comprising over half (by weight) of poppy seed, safflower, sunflower, corn, and soybean oils.
The major unsaturated fatty acids in soybean oil triglycerides are the polyunsaturates alpha-linolenic acid (C-18:3), 7-10%, and linoleic acid (C-18:2), 51%; and the monounsaturate oleic acid (C-18:1), 23%.

Lipoxygenase

lipoxygenaseslipoxidase5-lipoxygenase
In addition, LA is converted by various lipoxygenases, cyclooxygenases, certain cytochrome P450 enzymes (the CYP monooxygenases), and non-enzymatic autoxidation mechanisms to mono-hydroxyl products viz., 13-Hydroxyoctadecadienoic acid and 9-Hydroxyoctadecadienoic acid; these two hydroxy metabolites are enzymatically oxidized to their keto metabolites, 13-oxo-octadecadienoic acid and 9-oxo-octadecdienoic acid.
Polyunsaturated fatty acids that serve as substrates for one or more of the lipoxygenases include the omega 6 fatty acids, arachidonic acid, linoleic acid, dihomo-γ-linolenic acid, and adrenic acid; the omega-3 fatty acids, eicosapentaenoic acid, docosahexaenoic acid, and alpha-linolenic acid; and the omega-9 fatty acid, mead acid.

TRPV1

capsaicin receptorheat sensorshuman vanilloid receptor VR1
The oxidized metabolic products of linoleic acid, such as 9-hydroxyoctadecanoic acid and 13-hydroxyoctadecanoic acid, have also been shown to activate TRPV1, the capsaicin receptor, and through this might play a major role in hyperalgesia and allodynia.
The metabolites of linoleic acid, including 13(S)-hydroxy-9Z,11E-octadecadienoic acid (13(S)-HODE), 13(R)-hydroxy-9Z,11E-octadecadienoic acid (13(R)-HODE, 9(S)-hydroxy-10(E),12(Z)-octadecadienoic acid (9(S)-HODE), 9(R)-hydroxy-10(E),12(Z)-octadecadienoic acid (9(R)-HODE), and their respective keto analogs, 13-oxoODE and 9-oxoODE (see 13-HODE and 9-HODE sections on Direct actions), activate peripheral and central mouse pain sensing neurons.

Safflower

safflower oilCarthamus tinctoriusCarthami Flos
It is abundant in many nuts, fatty seeds (flax seeds, hemp seeds, poppy seeds, sesame seeds, etc.) and their derived vegetable oils; comprising over half (by weight) of poppy seed, safflower, sunflower, corn, and soybean oils.
There are two types of safflower that produce different kinds of oil: one high in monounsaturated fatty acid (oleic acid) and the other high in polyunsaturated fatty acid (linoleic acid).

Epoxygenase

cytochrome P450 epoxygenase
Certain cytochrome P450 enzymes, the CYP epoxygenases, metabolize LA to epoxide products viz., its 12,13-epoxide, Vernolic acid and its 9,10-epoxide, Coronaric acid.
However, the CYP epoxygenases also metabolize other omega-6 fatty acids such as linoleic acid and the omega-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid.

Gamma-Linolenic acid

γ-linolenic acidgamolenic acid(6''Z'',9''Z'',12''Z'')-octadeca-6,9,12-trienoic acid
The first step in the metabolism of linoleic acid is performed by Δ 6 desaturase, which converts LA into gamma-Linolenic acid (GLA).
The human body produces GLA from linoleic acid (LA).

Fatty acid desaturase

desaturasedesaturasesdesaturation
The first step in the metabolism of linoleic acid is performed by Δ 6 desaturase, which converts LA into gamma-Linolenic acid (GLA).
Δ 6 and Δ 5 desaturases are required for the synthesis of highly unsaturated fatty acids such as eicosopentaenoic and docosahexaenoic acids (synthesized from α-linolenic acid); arachidonic acid and adrenic acid (synthesized from linoleic acid).

Sesame oil

sesame seed oilsesamegingelly oil
Sesame oil is composed of the following fatty acids: linoleic acid (41% of total), oleic acid (39%), palmitic acid (8%), stearic acid (5%) and others in small amounts.

Corn oil

corncorn oilscorn-oil
It is abundant in many nuts, fatty seeds (flax seeds, hemp seeds, poppy seeds, sesame seeds, etc.) and their derived vegetable oils; comprising over half (by weight) of poppy seed, safflower, sunflower, corn, and soybean oils.

Grape seed oil

grapeseed oilgrapeseed
A study of 21 grape cultivars showed variation of oil composition, especially for linoleic acid and tocopherols.

Olive oil

extra virgin olive oiloilextra-virgin olive oil
It consists mainly of oleic acid (up to 83%), with smaller amounts of other fatty acids including linoleic acid (up to 21%) and palmitic acid (up to 20%).