Vernolic acid (leukotoxin B[1]) is a
long chain fatty acid that is
monounsaturated and contains an
epoxide. It is the R,R-cis epoxide derived from the C12–C13 alkene of
linoleic acid.[2] Vernolic acid was first definitively characterized in 1954.[3] It is a major component in vernonia oil, which is produced in abundance by the genera Vernonia and Euphorbia and is a potentially useful biofeedstock.
Occurrence
Vernonia oil is extracted from the seeds of the Vernonia galamensis (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.
Vernonia oil has been proposed as a precursor to
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.[5]
In its application as an
epoxy oil,[6] 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 comparable to partially epoxidized linseed or soybean oil.[7]
Toxicity
In a variety of mammalian species, vernolic acid is made by the metabolism of
linoleic acid by
cytochrome P450epoxygenase 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.[8][9] 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).[10][9] 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).
^Metzger, J. O.; Bornscheuer, U. (2006). "Lipids as renewable resources: current state of chemical and biotechnological conversion and diversification". Applied Microbiology and Biotechnology. 71 (1): 13–22.
doi:
10.1007/s00253-006-0335-4.
PMID16604360.
S2CID28601501.
^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.
^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.
^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.
PMID10775319.