Gyromitrin - Choose your mushrooms wisely

  • toxic hydrazine derivative found primarily in the cup fungi (mushrooms) Gyromitra esculenta, Gyromitra fastigiata, Gyromitra ambigua and Helvella lacunosa
    • these species are referred to as false morels, since they resemble in their appearance the true morels, which are yummy non-poisonous mushrooms belonging to the genus Morchella
    • both types of morels appear very early on in the springtime, so the rogue mushroom picker should exercise caution in his/her pickings (see also: lots and lots of other poisonous mushrooms)
  • volatile and water soluble, such that mushrooms containing it can usually be rendered safely edible by cuttin' 'em up into wee pieces and then boiling or pan-frying the bejesus of of 'em (releasing the toxin into the water or air, so cooks beware!)
  • metabolized (by hydrolysis) in the body first to methyl-N-formylhydrazine (MFH) and then on to something called monomethylhydrazine (MMH)
    • MMH is structurally similar to isoniazid (an antituberculous drug) and can be used as a friggin' rocket fuel (propellant, specifically) in bipropellant rocket engines (hydrazine, the parent form of MMH, is also a rocket fuel)
    • MFH is also way toxic, being capable of causing hemolysis, seizures, and liver necrosis (widespread cell death), which can lead to liver and kidney failure
    • MMH can cause seizures (often to the point of status epilepticus) by inhibiting the formation of GABA, the primary inhibitory neurotransmitter in the brain (less GABA means an increased propensity for the brain to become overexcited and throw a seizure)
    • it inhibits GABA formation by reacting with and so depleting pyridoxal-5-phosphate, which is the active form of vitamin B6 and a required coenzyme for the synthesis of GABA from glutamate by the enzyme glutamic acid decarboxylase (GAD)
      • can treat gyromitrin poisoning (at least the seizures) with pyridoxine (another form of vitamin B6) to antagonize it's GABA-related effects
    • MMH-induced seizures are resistant to benzos (just like seizures caused by isoniazid overdose)
  • has been shown to be carcinogenic in lab animals (even in very small doses) but there are no reports of it causing cancer in humans
Berger KJ, Guss DA. Mycotoxins revisited: Part II. J Emerg Med. 2005 Feb;28(2):175-83.

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