Guanitoxin

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Guanitoxin
Names
IUPAC name
(5S)-5-[(Dimethylamino)methyl]-1-{[hydroxy(methoxy)phosphoryl]oxy}-4,5-dihydro-1H-imidazol-2-amine
Identifiers
3D model (
JSmol
)
ChemSpider
KEGG
UNII
  • InChI=1S/C7H17N4O4P/c1-10(2)5-6-4-9-7(8)11(6)15-16(12,13)14-3/h6H,4-5H2,1-3H3,(H2,8,9)(H,12,13)/t6-/m1/s1
    Key: FYXHGVMFJYHPFX-ZCFIWIBFSA-N
  • CN(C)C[C@H]1CN=C(N1OP(=O)(O)OC)N
Properties
C7H17N4O4P
Molar mass 252.211 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Guanitoxin (GNT), formerly known as anatoxin-a(S) "Salivary"[a],[1] is a naturally occurring cyanotoxin commonly isolated from cyanobacteria (specifically of the genus Anabaena). It is a potent covalent acetylcholinesterase inhibitor, and thus a potent rapid acting neurotoxin which in cases of severe exposure can lead to death. Guanitoxin was first structurally characterized in 1989, and consists of a cyclic N-hydroxyguanine organophosphate with a phosphate ester moiety.[2]

Toxicity and treatment

The main mechanism of action for guanitoxin is by irreversibly inhibiting the active site of acetylcholinesterase leading to excess

lacrimation, chromodacryorrhea (in rats), urinary incontinence, muscular weakness, muscle twitching, convulsion, including opisthotonus, and respiratory distress and/or failure, and death.[4][5]

Treatment of afflicted case by atropine has attested to suppress the muscarinic mediated toxicity; which prevents the namesake salivation that similarly reacts to prevent the toxin's other poisoning symptoms which include lacrimation, urinary incontinence and defecation. Atropine will not, however, counter another mechanism of the compounds toxicity as it also mediates a nicotinic adverse toxicity affecting muscle tremors, fasciculation, convulsions and respiratory failure.[citation needed]

Stability and degradation

Guanitoxin is generally labile. It decomposes rapidly in basic solutions, but is relatively stable in neutral or acidic solutions (pH 3-5). When stored at -20˚C, it slowly undergoes hydrolysis giving (5S)-5-[(dimethylamino)methyl]-2-imino-1-imidazolidinol and monomethyl-phosphate, and more slowly, formation of (S)-1-(2-iminoimidazolidin-4-yl)-N,N-dimethylmethanamine. Furthermore, air evaporation of guanitoxin solutions resulted in significant hydrolysis to (5S)-5-[(dimethylamino)methyl]-2-imino-1-imidazolidinol.[2]

Scheme for guanitoxin degradation. Major microspecies at pH 7.4 are shown.

See also

  • Anatoxin-a – a cyanotoxin that shares some clinical exposure signs, and also relates to the same cyanobacteria genera, but with a different chemical structure and toxic mechanism of action
  • Paraoxon – A synthetic pesticide with an analogous mechanism of action

Footnotes

  1. ^ (The "(S)" its name stands for 'salivary' indicating its manner of affliction to distinguish it from a toxin having otherwise the same conventional name. cf. "See also" for aforementioned compound of shared nomenclature.)

References

  1. S2CID 211725815
    .
  2. ^
    ISSN 0002-7863
    .
  3. PMID 1770503
    .
  4. PMID 3087030
    .
  5. PMID 33227987
    .
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