Poisonous mushroom blamed for unexplained deaths in China

Feb 13, 2012, 3:05 GMT

Berlin - A previously unknown poisonous mushroom is the culprit in scores of mysterious deaths in China, according to a team of Chinese researchers who reported their findings in the German journal Angewandte Chemie (Applied Chemistry).

Over the past 30 years, more than 260 otherwise perfectly healthy people in the south-western Chinese province of Yunnan have died suddenly and for no apparent reason. The phenomenon, termed 'sudden unexplained death,' usually occurs during the rainy season from June to August at locations between 1,800 and 2,400 metres above sea level.

In 2005, epidemiological studies suggested that eating mushrooms could be a risk factor. Subsequent studies confirmed the suspicion that consumption of a previously unknown type of mushroom, named 'Trogia venenata Zhu L. Yang' after its discoverer, was responsible for the deaths.

The researchers, from the Kunming Institute of Botany and the Chinese Centre for Disease Control and Prevention, said they had now isolated and characterized three toxic amino acids from the fruiting bodies of the mushrooms in order to further prove their hypothesis: ¿-guanidinobutyric acid, which was already known, as well as two unusually toxic and previously unknown amino acids.

A crude extract from the mushroom was separated by liquid chromatography and the toxic amino acids were isolated, the research team reported. Their structure was identified with the help of various spectroscopic procedures, the compounds were synthesized in a laboratory and compared with natural compounds. The newly discovered amino acids have a terminal ethynyl group in common, a triple bond between two carbon atoms, the researchers said.

The toxicity of both amino acids was demonstrated in tests with mice. The researchers also analyzed a blood sample from a victim of 'sudden unexplained death' and said they had detected one of the toxic mushroom amino acids.

According to the researchers, all observations to date indicate that the Trogia venenata mushroom is the cause of the unexplained deaths. A campaign warning inhabitants of Yunnan against eating the mushroom has had successful results, they said: No further cases of 'sudden unexplained deaths' were recorded in 2010 and 2011.