Deadly mushroom toxin identified: synthetic muscle-destroying compound also found in nature.

A toadstool toxin that spurs convulsions, nausea, impaired speech and muscle stiffness--and has led to several deaths in Japan in recent years--has been isolated and identified by a team of scientists. The small molecule is familiar to synthetic chemists but had never been isolated from a natural source, researchers report online May 24 in Nature Chemical Biology.

Acute poisoning that leads to a breakdown of skeletal muscle tissue--a syndrome known as rhabdomyolysis--is not often caused by a mushroom and is quite different from the effects of toxins produced by the notorious death cap and death angel, comments Petteri Nieminen of the University of Joensuu in Finland.

The toxicity of Russula subnigrieans, the species identified in the new study, has barely been looked at, Nieminen said. The work "might bring this type of poisoning more to the foreground of mushroom studies."

Led by Kimiko Hashimoto of Kyoto Pharmaceutical University and Masaya Nakata of Keio University in Yokohama, Japan, the research team first isolated the toxin, a difficult task because the compound tends to bind to other things. Various spectroscopic analyses established the toxin's structure: a small, 4-carbon molecule known as cycloprop-2-ene carboxylic acid.

The team found the mushrooms and the isolated compound were lethal to mice, bringing about the unusual rhabdomyolysis when ingested.