8 April 2019

Muscarine - mushroom hunting can be a dangerous sport

Natural toxin

Wild forms of mushrooms are often poisonous and visually mimic the edible ones, thus leading to mistaken harvesting, consumption and toxicities.

Muscarine is a toxic alkaloid found in certain mushrooms, particularly in Inocybe and Clitocybe species. It is associated with toxicity when poisonous mushrooms are ingested. Muscarine is first parasympathomimetic substance ever studied and causes profound parasympathetic activation that may end in convulsions and death.

Figure 1: Amanita muscaria   

Muscarine, a water-soluble toxin was first isolated from the mushroom species Amanita muscaria (Figure 1). High concentration of this natural toxin can be found in Inocybe, Clitocybespecies and deadly C. dealbata. Mushrooms in the genera Entoloma and Mycena have also been found to contain levels of muscarine, which can be dangerous if ingested.

Figure 2. The structural formula of muscarine. Click for interactive 3D image 

There are two mirror forms of muscarine, named: 2S-muscarine and 2R-muscarine. Muscarine mimics the function of the natural neurotransmitter acetylcholine in the muscarinic part of the cholinergic nervous system. The muscarinic acetylcholine receptors (AChRs) are named from M1-M5 belong to the family of G-protein-coupled receptors (‘G proteins’). They are involved with the various autonomic physiological functions of the human body.

Muscarinic toxicity presents with an unusual and unique constellation of symptoms but may also go unrecognized. The usual symptoms and signs associated with muscarinic stimulation are exhaustion, irritability, muscular cramps, salivation, frothing, sweating, lacrimation, blurring of vision, miosis, ptosis, bronchorrhea, cough, tachypnea, bronchospasm, bradycardia, hypotension, abdominal cramps, vomiting, and diarrhea. Clinical signs of cholinergic overstimulation usually develop between 0.5 and 2 hours after ingestion. In humans, the oral lethal dose of muscarine is estimated between 40 mg and 495 mg.

The specific antidote is atropine. Atropine is also an alkaloid and inhibits acetylcholine and thus muscarine by binding to muscarinic receptors. Other muscarinic antagonists are scopolamine and pirenzepine Mild muscarinic toxicities do not require any specific treatment and adequate hydration is good enough in its management.

SMILES: O[C@@H]1C[C@H](O[C@H]1C)C[N+](C)(C)C

References:

  • Erguven M, Yilmaz O, Deveci M, Aksu N, Dursun F, Pelit M, et al. Mushroom poisoning. Indian J Pediatr. 2007;74:847–52
  • George P, Hegde N. Muscarinic toxicity among family members after consumption of mushrooms. Toxicol Int. 2013;20(1):113-5.
  • Goldfrank LR. Mushrooms. In: Nelson LS, Lewin NA, Howland MA, Hoffman RS, Goldfrank LR, Flomenbaum NE, editors. Goldfrank's Toxicologic Emergencies. 9th ed. New York: McGraw-Hill; 2011. pp. 1522–36.
  • Stallard D, Edes TE. Muscarinic poisoning from medications and mushrooms. A puzzling symptom complex. Postgrad Med. 1989;85:341–5.

Pictures