Orellanine

Orellanine or Orellanin is a pyridine N-oxide and a crystalline alkaloid that is found naturally in some lifeforms, specifically certain fungi.

It has been found in at least 34 Cortinariaceae. [1]

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History

In Poland during the 1950s there was a small epidemic where over 100 people became ill. What caused the illness remained a mystery until 1952 when Polish physician Dr. S. Grzymała discovered that everyone suffering from the illness, which had by now claimed several lives, had eaten the mushroom Cortinarius orellanus.^[1]

In 1955 he isolated a substance from the fungus. He named it orellanine after the Latin name of the toadstool. Given orally to research animals, he produced the same reaction as in humans. [2]

In 1973 orellanine was discovered in the toadstool Cortinarius rubellus.

Chemistry

The chemical constitution of orellanine remained unknown until the Polish chemists Antkowiak and Gessner in the last half of the 1970s discovered that it belongs to a group of compounds called bipyridines, a double ring structure where both rings are principally a pyridine ring (a heterocyclic ring with one nitrogen atom). In the most stable form of orellanine, the nitrogen atoms are positively charged.[3]

An interesting feature of orellanine is its ability to bind aluminium ions to organic complexes.[4]

Toxicity

Bipyridines with positively charged nitrogen atoms were already known to be poisonous before the structure of orellanine was elucidated. The herbicides paraquat and diquat are toxic not only to plants, but also to animals including humans. Bipyridines with charged nitrogen atoms confound important redox reactions in organisms, ‘stealing’ one or two electrons and sometimes bypass the electrons into other and often undesirable redox reactions. The terminal product can be peroxide or superoxide ions, the latter of which is harmful to the cells. It is likely that orellanine works in the same way, although the process from disturbed redox reactions to the serious clinical kidney damage has not been properly resolved.

In humans, a characteristic of poisoning by the nephrotoxin orellanine is the long latency; the first symptoms usually do not appear until 2-3 days after ingestion and can in some cases take as long as 3 weeks. The first symptoms of orellanine poisoning are similar to the common flu (nausea, vomiting, stomach pains, headaches, myalgia, etc), these symptoms are followed by early stages of renal failure (immense thirst, frequent urination, pain on and around the kidneys) and eventually decreased or nonexistent urine output and other symptoms of renal failure occur. If left untreated death will follow.

The lethal dose of orellanine in mice is 12 to 20 mg per kg body weight,^[2][3] where it must be noted that this is the dose which leads to death within two weeks. From cases of orellanine-related mushroom poisoning in humans it seems that the lethal dose for humans is considerably lower.

Treatment

Although there is no known antidote against orellanine poisoning, early hospitalization can sometimes prevent serious injury and usually prevent death. Research is ongoing. Some treatments make use of anti-oxidant therapy and corticosteroids to help victims recover from their renal failure.^[4]

References

See also

• Lethal webcaps
• Cortinarius