γ-Linolenic acid

This article is about γ-Linolenic acid. For alpha-linolenic acid, see α-Linolenic acid. For linoleic acid (no "n"), see Linoleic acid.
γ-Linolenic acid
Names
Preferred IUPAC name
(6Z,9Z,12Z)-Octadeca-6,9,12-trienoic acid
Other names
Gamma-linolenic acid, gamolenic acid, GLA
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.107.263
UNII
  • InChI=1S/C18H30O2/c1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20/h6-7,9-10,12-13H,2-5,8,11,14-17H2,1H3,(H,19,20)/b7-6-,10-9-,13-12- Y
    Key: VZCCETWTMQHEPK-QNEBEIHSSA-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/h6-7,9-10,12-13H,2-5,8,11,14-17H2,1H3,(H,19,20)/b7-6-,10-9-,13-12-
    Key: VZCCETWTMQHEPK-QNEBEIHSBP
  • O=C(O)CCCC\C=C/C\C=C/C\C=C/CCCCC
Properties
C18H30O2
Molar mass 278.436 g·mol−1
Appearance Colorless oil
Pharmacology
D11AX02 (WHO)
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

γ-Linolenic acid or GLA (INN: gamolenic acid) is an n−6, or omega-6, fatty acid found primarily in seed oils. When acting on GLA, arachidonate 5-lipoxygenase produces no leukotrienes and the conversion by the enzyme of arachidonic acid to leukotrienes is inhibited.

Chemistry

GLA is categorized as an n−6 (also called ω−6 or omega-6) fatty acid, meaning that the first double bond on the methyl end (designated with n or ω) is the sixth bond. In physiological literature, GLA is designated as 18:3 (n−6). GLA is a carboxylic acid with an 18-carbon chain and three cis double bonds. It is a regioisomer of α-linolenic acid, which is a polyunsaturated n−3 (omega-3) fatty acid, found in rapeseed canola oil, soybeans, walnuts, flax seed (linseed oil), perilla, chia, and hemp seed.

History

GLA was first isolated from the seed oil of evening primrose. This herbal plant was grown by Native Americans to treat swelling in the body. In the 17th century, it was introduced to Europe and became a popular folk remedy, earning the name king's cure-all. In 1919, Heiduschka and Lüft extracted the oil from evening primrose seeds and described an unusual linolenic acid, which they name γ-. Later, the exact chemical structure was characterized by Riley.[1]

Although there are α- and γ- forms of linolenic acid, there is no β- form. One was once identified, but it turned out to be an artifact of the original analytical process.[2]

Sources

Dietary sources

GLA is relatively rate in the human diet. It is present in small amounts in oats and barley.[3] According to the USDA Standard Release, it is present in hemp seeds (1.34% by mass), some vegetable oil products (0.59% in soft margarine), and some meats (0.1% in chicken skin).[4] USDA lists it as not found in canola, soybean, corn, coconut, or flaxseed oil, which is surprising given the reported presence in margarine and salad dressings.[5]

Spirulina lipid contains 18-21% GLA.[6] However, only 7.8% of Spirulina is lipid by dry mass, so the overall content by dry mass is closer to 1.23%.[7][8]

Human biosynthesis

The human body produces GLA from linoleic acid (LA). This reaction is catalyzed by Δ6-desaturase (D6D), an enzyme that allows the creation of a double bond on the sixth carbon counting from the carboxyl terminus. LA is consumed sufficiently in most diets, from such abundant sources as cooking oils and meats. However, a lack of GLA can occur when there is a reduction of the efficiency of the D6D conversion (for instance, as people grow older or when there are specific dietary deficiencies) or in disease states wherein there is excessive consumption of GLA metabolites.[9]

Concentrated sources

Significant amounts of GLA are found in specialty seed oils[10] such as evening primrose (Oenothera biennis) oil (EPO, 8–14%), blackcurrant seed oil (15–20%), borage seed oil (17-25%), Lithospermum purpurocaeruleum oil (18%), Onosmodium molle oil (20%), Symphaticum officinale oil (27%), and hemp seed oil (0.5–4.5%).[6] Normal safflower (Carthamus tinctorius) oil does not contain GLA, but a genetically modified GLA safflower oil available in commercial quantities since 2011 contains 40% GLA.[11] These concentrated sources are useful in the production of GLA dietary supplements.

Fungi are also prolific producers of GLA. Some fungi produce biomass with lipid levels comparable to seeds (up to 70% by dry mass). These fungi can therefore be grown industrially to obtain large amounts of GLA-rich (13.2–49%) fungal lipids.[6] The fungi Mucor circinelloides and Mucor plumbeus are prolific producers of GLA, efficient enough for industrial use.[12][13] Other useful fungi include Mortierella vinacea, Mortierella ramanniana, Mortierella isabellina, Rhizopus stolonifera, Rhizopus nigricans, Rhizopus oryzae, and Cunninghamella elegans.[6]

Source of eicosanoids

From GLA, the body forms dihomo-γ-linolenic acid (DGLA). This is one of the body's three sources of eicosanoids (along with AA and EPA.) DGLA is the precursor of the prostaglandin PGH1, which in turn forms PGE1 and the thromboxane TXA1. Both PGE11 and TXA1 are anti-inflammatory; thromboxane TXA1, unlike its series-2 variant, induces vasodilation, and inhibits platelet[14] consequently, TXA1 modulates (reduces) the pro-inflammatory properties of the thromboxane TXA2. PGE1 has a role in regulation of immune system function and is used as the medicine alprostadil.

Unlike AA and EPA, DGLA cannot yield leukotrienes. However, it can inhibit the formation of pro-inflammatory leukotrienes from AA.[15]

Although GLA is an n−6 fatty acid, a type of acid that is, in general, pro-inflammatory, it has anti-inflammatory properties. (See discussion at Essential fatty acid interactions: The paradox of dietary GLA.)

Topical use

In 2002, the UK Medicines and Healthcare products Regulatory Agency withdrew marketing authorisations for evening primrose oil as an eczema remedy.[16] The BMJ commented in 2003 that it had taken 20 years to demonstrate that the substance was of no use in atopic dermatitis, and called for more transparency in the research on which drug licensing decisions were taken.[17]

Notes and references

  1. ^ Yung-Sheng Huang, Vincent A. Ziboh (2001). Gamma-Linolenic Acid: Recent Advances in Biotechnology and Clinical Applications. AOCS Press. p. 259. ISBN 1-893997-17-0. Retrieved 2007-12-07.
  2. ^ Eckey, EW (1954). Vegetable Fats and Oils (volume 123 of American Chemical Society monograph series). Reinhold. p. 542.
  3. ^ Qureshi A.A.; Schnoes H.K.; Din Z.Z.; Peterson D.M.; et al. (1984). "Determination of the structure of cholesterol inhibitor II isolated from high-protein barley flour (HPBF)". Fed. Proc. 43 (7): 2626.
  4. ^ "Foods Highest in gamma-Linolenic Acid (GLA); per 100 grams". My Food Data.
  5. ^ "Fats and Oils Highest in gamma-Linolenic Acid (GLA)". My Food Data.
  6. ^ a b c d Latifi, Mojgan; Jalali Bidgoli, Foroozan; Hajihassani, Helia; Hassani, Danial; Ingvarsson, Pär K.; Farrokhi, Naser (9 July 2025). "Recent advances and future directions on GLA-producing organisms". Frontiers in Bioengineering and Biotechnology. 13. doi:10.3389/fbioe.2025.1567840.
  7. ^ Mendes, Rui L.; Reis, Alberto D.; Palavra, António F. (January 2006). "Supercritical CO2 extraction of γ-linolenic acid and other lipids from Arthrospira (Spirulina)maxima: Comparison with organic solvent extraction". Food Chemistry. 99 (1): 57–63. doi:10.1016/j.foodchem.2005.07.019.
  8. ^ Golmakani M.T.; Mendiola J.A.; Rezaei K.; Ibáñez E. (2012). "Expanded ethanol with CO
    2     and pressurized ethyl lactate to obtain fractions enriched in γ-Linolenic Acid from Arthrospira platensis (Spirulina)"    . J. Supercritical Fluids. 62: 109–115. doi:10.1016/j.supflu.2011.11.026. hdl:10261/43494.
  9. ^ Horrobin D.F. (From the Efamol Research Institute. Kentville. Nova Scotia. Canada) (1993). "Fatty acid metabolism in health and disease: the role of delta-6-desaturase". American Journal of Clinical Nutrition. 57 (5 Suppl): 732S–736S, discussion 736S–737S. doi:10.1093/ajcn/57.5.732S. PMID 8386433.
  10. ^ Flider, Frank J. (May 2005). "GLA: Uses and new sources" (PDF). INFORM. 16 (5): 279–282. Archived from the original (PDF) on 2014-01-12.
  11. ^ Nykiforuk, Cory L.; et al. (19 August 2011). "High level accumulation of gamma linolenic acid (C18:3Δ6,9,12 cis) in transgenic safflower (Carthamus tinctorius) seeds". Transgenic Research. 21 (2): 367–381. doi:10.1007/s11248-011-9543-5. PMID 21853296. S2CID 17870059.
  12. ^ Wu, Chen; Yang, Junhuan; Li, Shaoqi; Shi, Wenyue; Xue, Futing; Liu, Qing; Naz, Tahira; Mohamed, Hassan; Song, Yuanda (12 July 2023). "Construction of Eicosatetraenoic Acid Producing Cell Factory by Genetic Engineering of Mucor circinelloides". Fermentation. 9 (7): 653. doi:10.3390/fermentation9070653.
  13. ^ Mohamed, Hassan; Awad, Mohamed F.; Shah, Aabid Manzoor; Sadaqat, Beenish; Nazir, Yusuf; Naz, Tahira; Yang, Wu; Song, Yuanda (30 July 2022). "Coculturing of Mucor plumbeus and Bacillus subtilis bacterium as an efficient fermentation strategy to enhance fungal lipid and gamma-linolenic acid (GLA) production". Scientific Reports. 12 (1). doi:10.1038/s41598-022-17442-2.
  14. ^ King, Michael W. "Introduction to the Eicosanoids". The Medical Biochemistry Page. 1996–2013 themedicalbiochemistrypage.org, LLC. Retrieved 23 July 2013.
  15. ^ Belch JJ, Hill A (2000). "Evening primrose oil and borage oil in rheumatologic conditions". American Journal of Clinical Nutrition. 71 (1 Suppl): 352S–356S. doi:10.1093/ajcn/71.1.352s. PMID 10617996. DGLA itself cannot be converted to LTs but can form a 15-hydroxyl derivative that blocks the transformation of arachidonic acid to LTs. Increasing DGLA intake may allow DGLA to act as a competitive inhibitor of 2-series PGs and 4-series LTs and, thus, suppress inflammation.
  16. ^ Williams, H.C. (2003). "Evening primrose oil for atopic dermatitis: Time To Say Goodnight". BMJ. 327 (7428): 1358–9. doi:10.1136/bmj.327.7428.1358. JSTOR 25457999. PMC 292973. PMID 14670851.
  17. ^ Smith, R. (2003). "The drugs don't work". BMJ. 327 (7428): 0–h. doi:10.1136/bmj.327.7428.0-h.
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