Vernolic acid

Vernolic acid (leukotoxin) is a long chain fatty acid that is monounsaturated and contains an epoxide. It is the cis epoxide derived from the C12–C13 alkene of linoleic acid and exists both the (+)- and (−)- optical isomers.[1][2] It is an isomer of coronaric acid, the two enantiomeric forms resulting instead by epoxidation at the C9–C10 alkene.[3] Vernolic acid was first definitively characterized in 1954.[4] It is the key component in vernonia oil, which is produced in abundance by the genera Vernonia and Euphorbia and is a potentially useful biofeedstock.

Vernolic acid
Names
IUPAC name
(+)-(12S,13R)-Epoxy-cis-9-octadecenoic acid
Other names
Racemic:
  • Linoleic acid 12:13-oxide
  • cis-12-epoxyoctadeca-cis-9-enoic acid

Single-enantiomer (corresponding to IUPAC-name isomer):

  • (+)-(12S,13R)-epoxy-cis-9-octadecenoic acid
  • 12S,13R-EpOME
  • (9Z)-(12S,13R)-12,13-epoxyoctadecenoic acid
Identifiers
3D model (JSmol)
ChemSpider
UNII
Properties
C18H32O3
Molar mass 296.451 g·mol−1
Appearance Colorless oil
Melting point 23 to 25 °C (73 to 77 °F; 296 to 298 K)
Insoluble
Solubility in other solvents organic solvents
Hazards
Main hazards flammable
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Toxicity

In a variety of mammalian species, vernolic acid is made by the metabolism of linoleic acid by certain cytochrome P450 epoxygenase enzymes; under these circumstances it is termed leukotoxin because of its toxic effects on leukocytes and other cell types and of its ability to produce multiple organ failure and respiratory distress when injected into rodent animal models of the acute respiratory distress syndrome.[5][6] These effects appear due to the conversion of vernolic acid to its dihydroxy counterparts, 12S,13R- and 12R,13S-dihydroxy-cis-9-octadecenoic acids by soluble epoxide hydrolase (this dihydroxy mixture has been termed leukotoxin diol).[7][6] Some studies suggest but have not yet proven that vernolic acid is responsible for or contributes to multiple organ failure, respiratory distress, and certain other cataclysmic diseases in humans (see epoxygenase subsection on linoleic acid).

Vernonia oil

Vernonia oil is extracted from the seeds of the Vernonia galamensis (or ironweed), a plant native to eastern Africa. The seeds contain about 40 to 42% oil of which 73 to 80% is vernolic acid. The best varieties of V. anthelmintica contain about 30% less vernolic acid. Products that can be made from vernonia oil include epoxies for manufacturing adhesives, varnishes and paints, and industrial coatings. Its low viscosity recommends its use as a nonvolatile solvent in oil-based paints since it will become incorporated in the dry paint rather than evaporating into the air.[8]

This use of vernonia oil offers potential environmental benefits, since its use could reduce emissions associated with man-made chemicals.

In its application as an epoxy oil,[9] vernonia oil competes with soybean or linseed oil, which supply most of the market for these applications. Its low viscosity makes it more desirable than fully epoxidized linseed or soybean oils. It is more comparable to partially epoxidized linseed or soybean oil.[10]

Other plant sources

Vernolic acid is not commonly found in plants in significant quantities, but some plants which do contain it are Vernonia, Stokesia, Crepis (from the daisy family), and Euphorbia lagascae and Bernardia pulchella from the Euphorbiaceae.[11]

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References
  1. CID 6449780 from PubChem
  2. "CHEBI:38300 - (−)-vernolic acid". Chemical Entities of Biological Interest (ChEBI). European Bioinformatics Institute (EBI).
  3. CID 6246154 from PubChem
  4. Gunstone FD (1954). "Fatty acids. Part II. The nature of the oxygenated acid present in Vernonia anthelmintica (Willd.) seed oil". Journal of the Chemical Society. 1954: 1611–1616. doi:10.1039/JR9540001611.
  5. Linhartová I, Bumba L, Mašín J, Basler M, Osička R, Kamanová J, Procházková K, Adkins I, Hejnová-Holubová J, Sadílková L, Morová J, Sebo P (November 2010). "RTX proteins: a highly diverse family secreted by a common mechanism". FEMS Microbiology Reviews. 34 (6): 1076–112. doi:10.1111/j.1574-6976.2010.00231.x. PMC 3034196. PMID 20528947.
  6. Spector AA, Kim HY (April 2015). "Cytochrome P450 epoxygenase pathway of polyunsaturated fatty acid metabolism". Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids. 1851 (4): 356–65. doi:10.1016/j.bbalip.2014.07.020. PMC 4314516. PMID 25093613.
  7. Greene JF, Newman JW, Williamson KC, Hammock BD (April 2000). "Toxicity of epoxy fatty acids and related compounds to cells expressing human soluble epoxide hydrolase". Chemical Research in Toxicology. 13 (4): 217–26. doi:10.1021/tx990162c. PMID 10775319.
  8. Teynor TM, Putnam DJ, Oplinger ES, Oelke EA, Kelling KA, Doll JD (February 1992). "Vernonia". Alternative Field Crops Manual. Retrieved 2006-09-10.
  9. Mohamed AI, Mebrahtu T, Andebrhan T (1999). Janick J (ed.). "Variability in oil and vernolic acid contents in the new Vernonia galamensis collection from East Africa". Perspectives on New Crops and New Uses: 272–274. Retrieved 2006-09-10.
  10. Muturi P, Wang D, Dirlikov S (1994). "Epoxidized vegetable oils as reactive diluents I. Comparison of vernonia, epoxidized soybean and epoxidized linseed oils". Progress in Organic Coatings. 25: 85–94. doi:10.1016/0300-9440(94)00504-4.
  11. Cahoon EB, Ripp KG, Hall SE, McGonigle B (February 2002). "Transgenic production of epoxy fatty acids by expression of a cytochrome P450 enzyme from Euphorbia lagascae seed". Plant Physiology. 128 (2): 615–24. doi:10.1104/pp.010768. PMC 148923. PMID 11842164.
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