Experts identify toxic compound in deadly mushroom

HONG KONG (Reuters) - Scientists have said they had identified the toxin in a species of mushroom that killed seven people in Japan in recent years.

In an article published in Nature Chemical Biology on Monday, the researchers said they isolated the poisonous compound in the mushroom, Russula subnigricans, and confirmed its toxicity by feeding it to mice.

The toxin, cycloprop-2-ene carboxylic acid, has only four carbon atoms.

"We ascertained that this toxin causes severe rhabdomyolysis on mice ... which means that this toxin is the responsible toxin causing the mushroom poisoning," one of the researchers, Kimiko Hashimoto at Kyoto Pharmaceutical University, told Reuters.

Apart from the usual symptoms of poisoning, such as nausea, diarrhoea, speech impairment, convulsions, pupil contractions, stiff shoulders and backaches, the human victims in Japan also suffered rhabdomyolysis, which is rarely seen.

Rhabdomyolysis is the rapid breakdown of skeletal muscle tissue due to muscle injury. This leads to the release of the protein myoglobin into the bloodstream which harms the kidney.

Myoglobin was found in the urine of the Japanese victims.

Hashimoto said an adult person would die eating just two or three such mushrooms.

"Medical doctors who meet such cases should give care to protect the kidney. Rhabdomyolysis produces a large quantity of myoglobin, which is a heavy burden to the kidney. So, rhabdomyolysis leads to renal failure and then leads to death," Hashimoto wrote in an email to Reuters.