Α-Linolenic acid

This article is about α-Linolenic acid. For other uses, see Linolenic acid.

α-Linolenic acid, also known as alpha-linolenic acid (ALA) (from Greek alpha meaning "first" and linon meaning flax), is an n−3, or omega-3, essential fatty acid. ALA is found in many seeds and oils, including flaxseed, walnuts, chia, hemp, and many common vegetable oils.

α-Linolenic acid

Names
Preferred IUPAC name (9Z,12Z,15Z)-Octadeca-9,12,15-trienoic acid[1]
Other names ALA; LNA; Linolenic acid; cis,cis,cis-9,12,15-Octadecatrienoic acid; (9Z,12Z,15Z)-9,12,15-Octadecatrienoic acid; Industrene 120
Identifiers
CAS Number	463-40-1 Y
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:27432 Y
ChEMBL	ChEMBL8739 Y
ChemSpider	4444437 Y
DrugBank	DB00132 Y
ECHA InfoCard	100.006.669
IUPHAR/BPS	1049
PubChem CID	5280934
UNII	0RBV727H71 Y
CompTox Dashboard (EPA)	DTXSID7025506
InChI InChI=1S/C18H30O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20/h3-4,6-7,9-10H,2,5,8,11-17H2,1H3,(H,19,20)/b4-3-,7-6-,10-9- Y Key: DTOSIQBPPRVQHS-PDBXOOCHSA-N Y InChI=1/C18H30O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20/h3-4,6-7,9-10H,2,5,8,11-17H2,1H3,(H,19,20)/b4-3-,7-6-,10-9- Key: DTOSIQBPPRVQHS-PDBXOOCHBH
SMILES O=C(O)CCCCCCC\C=C/C\C=C/C\C=C/CC CC/C=C\C/C=C\C/C=C\CCCCCCCC(=O)O
Properties
Chemical formula	C18H30O2
Molar mass	278.436 g·mol−1
Density	0.9164 g/cm3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

In terms of its structure, it is named all-cis-9,12,15-octadecatrienoic acid.^[2] In physiological literature, it is listed by its lipid number, 18:3 (n−3). It is a carboxylic acid with an 18-carbon chain and three cis double bonds. The first double bond is located at the third carbon from the methyl end of the fatty acid chain, known as the n end. Thus, α-linolenic acid is a polyunsaturated n−3 (omega-3) fatty acid. It is a regioisomer of gamma-linolenic acid (GLA), an 18:3 (n−6) fatty acid (i.e., a polyunsaturated omega-6 fatty acid with three double bonds).

Etymology

The word linolenic is an irregular derivation from linoleic, which itself is derived from the Greek word linon (flax). Oleic means "of or relating to oleic acid" because saturating an omega-6 double bond of linoleic acid produces oleic acid. Similarly saturating one of linolenic acid's double bonds produces linoleic acid.

Dietary sources

See also: Vegetable oil § Composition of fats

Seed oils are the richest sources of α-linolenic acid, notably those of hempseed, chia, perilla, flaxseed (linseed oil), rapeseed (canola), and soybeans. α-Linolenic acid is also obtained from the thylakoid membranes in the leaves of Pisum sativum (pea leaves).^[3] Plant chloroplasts consisting of more than 95 percent of photosynthetic thylakoid membranes are highly fluid due to the large abundance of ALA, evident as sharp resonances in high-resolution carbon-13 NMR spectra.^[4] Some studies state that ALA remains stable during processing and cooking.^[5] However, other studies state that ALA might not be suitable for baking as it will polymerize with itself, a feature exploited in paint with transition metal catalysts. Some ALA may also oxidize at baking temperatures.^[6] ALA percentages in the table below refer to the oils extracted from each item.

Common name	Alternate name	Linnaean name	% ALA†(of oil)	ref.
Chia	chia sage	Salvia hispanica	64%	[7]
Kiwifruit seeds	Chinese gooseberry	Actinidia chinensis	62%	[7]
Perilla	shiso	Perilla frutescens	58%	[7]
Flax	linseed	Linum usitatissimum	55%	[7]
Lingonberry	cowberry	Vaccinium vitis-idaea	49%	[7]
Camelina	camelina	Camelina sativa	37%	[8]
Purslane	portulaca	Portulaca oleracea	35%	[7]
Cuckoo flower	mayflower	Cardamine pratensis	35%	[9]
Cranberry	American cranberry	Vaccinium macrocarpon	35%	[9]
Sea buckthorn	seaberry	Hippophae rhamnoides L.	32%	[10]
Raspberry	raspberry	Rubus idaeus	31%	[9]
Blueberry	bilberry	Vaccinium myrtillus L.	29%	[9]
Hemp	cannabis	Cannabis sativa	20%	[7]
Walnut	English walnut / Persian walnut	Juglans regia	10.4%	[11]
Rapeseed	canola	Brassica napus	10%	[2]
Soybean	soya	Glycine max	8%	[2]
			†average value

Metabolism

Flax is a rich source of α-linolenic acid.

α-Linolenic acid can be obtained by humans only through their diets. Humans lack the desaturase enzymes required for processing stearic acid into A-linoleic acid or other unsaturated fatty acids.

Dietary α-linolenic acid is metabolized to stearidonic acid, a precursor to a collection of polyunsaturated 20-, 22-, 24-, etc fatty acids (eicosatetraenoic acid, eicosapentaenoic acid, docosapentaenoic acid, tetracosapentaenoic acid, 6,9,12,15,18,21-tetracosahexaenoic acid, docosahexaenoic acid).^[12] Because the efficacy of n−3 long-chain polyunsaturated fatty acid (LC-PUFA) synthesis decreases down the cascade of α-linolenic acid conversion, DHA synthesis from α-linolenic acid is even more restricted than that of EPA.^[13] Conversion of ALA to DHA is higher in women than in men.^[14]

Stability and hydrogenation

Compared to many other oils, α-linolenic acid is more susceptible to oxidation. It becomes rancid more quickly in air. Oxidative instability of α-linolenic acid is one reason why producers choose to partially hydrogenate oils containing α-linolenic acid, such as soybean oil.^[15] Soybeans are the largest source of edible oils in the U.S., and, as of a 2007 study, 40% of soy oil production was partially hydrogenated.^[16]

Hydrogenation of ALA-containing fats can introduce trans fats. Consumers are increasingly avoiding products that contain trans fats, and governments have begun to ban trans fats in food products. These regulations and market pressures have spurred the development of soybeans low in α-linolenic acid. These new soybean varieties yield a more stable oil that often do not require hydrogenation for many applications.^[17]

Health

ALA consumption is associated with a lower risk of cardiovascular disease and a reduced risk of fatal coronary heart disease.^[18][19] Dietary ALA intake can improve lipid profiles by decreasing triglycerides, total cholesterol, high-density lipoprotein, and low-density lipoprotein.^[20] A 2021 review found that ALA intake is associated with a reduced risk of mortality from all causes, cardiovascular disease, and coronary heart disease but a slightly higher risk of cancer mortality.^[21]

History

In 1887, linolenic acid was discovered and named by the Austrian chemist Karl Hazura of the Imperial Technical Institute at Vienna (although he did not separate its isomers).^[22] α-Linolenic acid was first isolated in pure form in 1909 by Ernst Erdmann and F. Bedford of the University of Halle an der Saale, Germany,^[23] and by Adolf Rollett of the Universität Berlin, Germany,^[24] working independently, as cited in J. W. McCutcheon's synthesis in 1942,^[25] and referred to in Green and Hilditch's 1930s survey.^[26] It was first artificially synthesized in 1995 from C6 homologating agents. A Wittig reaction of the phosphonium salt of [(Z-Z)-nona-3,6-dien-1-yl]triphenylphosphonium bromide with methyl 9-oxononanoate, followed by saponification, completed the synthesis.^[27]

See also

• Canola oil
• Flax seed oil
• gamma-Linolenic acid
• Drying oil
• Essential fatty acid
• List of n−3 fatty acids
• Essential nutrient
• Wheat germ oil

References

1. Loreau O, Maret A, Poullain D, Chardigny JM, Sébédio JL, Beaufrère B, Noël JP (2000). "Large-scale preparation of (9Z,12E)-[1-¹³C]-octadeca-9,12-dienoic acid, (9Z,12Z,15E)-[1-¹³C]-octadeca-9,12,15-trienoic acid and their 1-¹³C all-cis isomers". Chemistry and Physics of Lipids. 106 (1): 65–78. doi:10.1016/S0009-3084(00)00137-7. PMID 10878236.
2. Beare-Rogers (2001). "IUPAC Lexicon of Lipid Nutrition" (PDF). Archived (PDF) from the original on 12 February 2006. Retrieved 22 February 2006.
3. Chapman, David J., De-Felice, John, Barber, James (May 1983). "Growth temperature effects on thylakoid membrane lipid and protein content of pea chloroplasts 1". Plant Physiol. 72 (1): 225–228. doi:10.1104/pp.72.1.225. PMC 1066200. PMID 16662966.
4. YashRoy R.C. (1987) 13-C NMR studies of lipid fatty acyl chains of chloroplast membranes. Indian Journal of Biochemistry and Biophysics vol. 24(6), pp. 177–178.https://www.researchgate.net/publication/230822408_13-C_NMR_studies_of_lipid_fatty_acyl_chains_of_chloroplast_membranes?ev=prf_pub
5. Manthey FA, Lee RE, Hall CA (2002). "Processing and cooking effects on lipid content and stability of alpha-linolenic acid in spaghetti containing ground flaxseed". J. Agric. Food Chem. 50 (6): 1668–71. doi:10.1021/jf011147s. PMID 11879055.
6. "OXIDATIVE STABILITY OF FLAXSEED LIPIDS DURING BAKING". Archived from the original on 16 October 2015. Retrieved 30 December 2012.
7. "Seed Oil Fatty Acids – SOFA Database Retrieval". Archived from the original on 9 November 2018. Retrieved 26 March 2018.
8. Juodka R, Nainiené R, Juškiené V, Juška R, Leikus R, Kadžiené G, Stankevičiené D (January 2022). "Camelina (Camelina sativa (L.) Crantz) as Feedstuffs in Meat Type Poultry Diet: A Source of Protein and n-3 Fatty Acids". Animals. 12 (3). Table 3. doi:10.3390/ani12030295. PMC 8833380. PMID 35158619.
9. Bederska-Łojewska D, Pieszka M, Marzec A, Rudzińska M, Grygier A, Siger A, Cieślik-Boczula K, Orczewska-Dudek S, Migdał W (December 2021). "Physicochemical Properties, Fatty Acid Composition, Volatile Compounds of Blueberries, Cranberries, Raspberries, and Cuckooflower Seeds Obtained Using Sonication Method". Molecules. 26 (24). Table 2. doi:10.3390/molecules26247446. PMC 8704999. PMID 34946523.
10. Li TS (1999). "Sea buckthorn: New crop opportunity". Perspectives on new crops and new uses. Alexandria, VA: ASHS Press. pp. 335–337. Archived from the original on 22 September 2006. Retrieved 28 October 2006.
11. "Omega-3 fatty acids". University of Maryland Medical Center. Archived from the original on 27 December 2009.
12. Breanne M Anderson, David WL Ma (2009). "Are all n-3 polyunsaturated fatty acids created equal?". Lipids in Health and Disease. 8 (33): 33. doi:10.1186/1476-511X-8-33. PMC 3224740. PMID 19664246.
13. Shiels M. Innis (2007). "Fatty acids and early human development". Early Human Development. 83 (12): 761–766. doi:10.1016/j.earlhumdev.2007.09.004. PMID 17920214.
14. Burdge GC, Calder PC (2005). "Conversion of alpha-linolenic acid to longer-chain polyunsaturated fatty acids in human adults" (PDF). Reproduction, Nutrition, Development. 45 (5): 581–597. doi:10.1051/rnd:2005047. PMID 16188209. Archived (PDF) from the original on 15 August 2017. Retrieved 4 November 2018.
15. Kinney, Tony. "Metabolism in plants to produce healthier food oils (slide #4)" (PDF). Archived from the original (PDF) on 29 September 2006. Retrieved 11 January 2007.
16. Fitzgerald, Anne, Brasher, Philip. "Ban on trans fat could benefit Iowa". Truth About Trade and Technology. Archived from the original on 27 September 2007. Retrieved 3 January 2007.
17. Monsanto. "ADM to process Monsanto's Vistive low linolenic soybeans at Indiana facility". Archived from the original on 11 December 2006. Retrieved 6 January 2007.
18. Sala-Vila A, Fleming J, Kris-Etherton P, Ros E (2022). "Impact of α-Linolenic Acid, the Vegetable ω-3 Fatty Acid, on Cardiovascular Disease and Cognition". Advances in Nutrition. 13 (5): 1584–1602. doi:10.1093/advances/nmac016. PMC 9526859. PMID 35170723.
19. Pan A, Chen M, Chowdhury R, et al. (December 2012). "α-Linolenic acid and risk of cardiovascular disease: a systematic review and meta-analysis". Am. J. Clin. Nutr. (Systematic review). 96 (6): 1262–73. doi:10.3945/ajcn.112.044040. PMC 3497923. PMID 23076616.
20. Hao Y, Bin Q, Min J, Wei L, Xiao-fei G, Na L, Zhi-xiang X, Fang-ling D, Tongcheng X, Duo L (2020). "Effects of α-linolenic acid intake on blood lipid profiles：a systematic review and meta-analysis of randomized controlled trials". Critical Reviews in Food Science and Nutrition. 61 (17): 2894–2910. doi:10.1080/10408398.2020.1790496. PMID 32643951. S2CID 220439436. Archived from the original on 14 December 2021. Retrieved 14 December 2021.
21. Naghshi S, Aune D, Beyene J, Mobarak S, Asadi M, Sadeghi O (2021). "Research Dietary intake and biomarkers of alpha linolenic acid and risk of all cause, cardiovascular, and cancer mortality: systematic review and dose-response meta-analysis of cohort studies". The BMJ. 375: n2213. doi:10.1136/bmj.n2213. PMC 8513503. PMID 34645650. Archived from the original on 14 December 2021. Retrieved 14 December 2021.
22. Hazura K (1887). "Über trocknende Ölsäuren IV. Abhandlung" [On drying oily acids 4th paper]. Monatshefte für Chemie (in German). 8: 260–270. doi:10.1007/BF01510049. S2CID 197767239. Archived from the original on 18 January 2021. Retrieved 1 November 2020. Linolenic acid is named on p. 265: "Für die Säure C₁₈H₃₂O₂ schlage ich den Namen Linolsäure, für die Säure C₁₈H₃₀O₂ den Namen Linolensäure vor." (For the acid C₁₈H₃₂O₂ I suggest the name "linolic acid"; for the acid C₁₈H₃₀O₂ [I suggest] the name "linolenic acid".) Linolenic acid is discussed on pp. 265-268.
23. See:

    • Erdmann E, Bedford F (1909). "Über die im Leinöl enthaltene Linolensäure" [On linolenic acid [that's] contained in flax oil]. Berichte der Deutschen Chemischen Gesellschaft (in German). 42: 1324–1333. doi:10.1002/cber.190904201217. Archived from the original on 26 January 2021. Retrieved 31 October 2020. On p. 1329 they distinguish one of the isomers of linolenic acid: "Wir bezeichnen diese in Leinöl vorhandene Linolensäure, welche das feste Hexabromid liefert, zum Unterschied von einer später zu erwähnenden Isomeren als α-Linolensäure." (We designate this linolenic acid, which the solid hexabromide [of linolenic acid] provides, as α-linolenic acid in order to distinguish [it] from an isomer [that will be] mentioned later.)
    • Erdmann E, Bedford F, Raspe F (1909). "Konstitution der Linolensäure" [Structure of linolenic acid]. Berichte der Deutschen Chemischen Gesellschaft (in German). 42: 1334–1346. doi:10.1002/cber.190904201218. Archived from the original on 1 February 2021. Retrieved 31 October 2020. The structure of α-linolenic acid appears on p. 1343.
24. Rollett, A. (1909). "Zur Kenntnis der Linolensäure und des Leinöls" [[Contribution to our] knowledge of linolenic acid and flax oil]. Zeitschrift für physiologische Chemie. 62 (5–6): 422–431. doi:10.1515/bchm2.1909.62.5-6.422. Archived from the original on 18 March 2020. Retrieved 1 July 2019.
25. J. W. McCutcheon (1955). "Linolenic acid". Organic Syntheses; Collected Volumes, vol. 3, p. 351.
26. Green TG, Hilditch TP (1935). "The identification of linoleic and linolenic acids". Biochem. J. 29 (7): 1552–63. doi:10.1042/bj0291552. PMC 1266662. PMID 16745822.
27. Sandri, J., Viala, J. (1995). "Direct preparation of (Z,Z)-1,4-dienic units with a new C6 homologating agent: synthesis of α-linolenic acid". Synthesis. 1995 (3): 271–275. doi:10.1055/s-1995-3906. S2CID 196696819.