Shroom doom: NMR reveals fatal attraction

Your poison

Nuclear magnetic resonance spectroscopy, mass spectrometry and other techniques have been used to demonstrate that the consumption of toxic mushrooms may have been responsible for a series of unexplained deaths in China during the last three decades.

There has been a series of unusual deaths in China's Yunnan province over the last 30 years. Apparently, more than 260 otherwise perfectly healthy individuals in this part of southwestern China died suddenly without apparent cause. Their deaths were written up as nothing more revealing than "sudden unexplained death". However, there were clues as to a possible cause of these deaths. The deaths occurred in clusters both in time and location. The majority occurred during the rainy period of June to August and in locations between 1800 and 2400 metres above sea level. Epidemiologists finally pinned down a possible cause that correlated with these factors in 2005 suggesting that the deaths were associated with collecting and eating wild mushrooms. Eventually, a specific but previously unknown species of mushroom was identified as the likely agent: Trogia venenata Zhu L. Yang.

Now, a team led by Ji-Kai Liu of the Chinese Center for Disease Control and Prevention, Beijing, China, has offered additional evidence that several unusual toxic amino acids found in extracts from suspect mushrooms possibly ingested by the victims of poisoning may be to blame. The scientists of the Kunming Institute of Botany and the Chinese Centre for Disease Control and Prevention have isolated and characterized three toxic compounds from the fruiting bodies of these mushroom in order to provide definitive evidence that T. venenata is the culprit. The fruiting body of a mushroom, is the visible spore-bearing cap of which many edible species are eaten. The compounds discovered by the team include the previously identified amino acid, gamma-guanidinobutyric acid, and two other unusual, unidentified toxic amino acids.

Crude and toxic

Crude extraction was carried out using liquid chromatography to isolate the toxic amino acids. Spectroscopy was then used to determine their structures. Subsequent synthesis of the compounds in the laboratory and comparison with the natural products pinned down the details. The team found that the two newly discovered amino acids have a terminal ethynyl group in common.

Tests in laboratory mice also confirmed the toxicity of the two amino acids. This coupled with analysis of blood samples from one victim of sudden unexplained death in the region revealed the presence of one of the toxic mushroom amino acids in their system. Although the details of the toxic compounds is only now being published a public awareness campaign in Yunnan Province has been ongoing since the mushroom Trogia venenata was first demonstrated as being the possible cause of the unexplained deaths. Indeed, the campaign has been rather successful and there were no further cases of "sudden unexplained death" during neither 2010 nor 2011.

What's your poison?

The team included Z.-Y. Zhou, K. Wei, T. Feng, F. Wang, G.-Q. Wang, Y. Qu, Z.-H. Li, Z.-J. Dong, H.-J. Zhu, Z.-L. Yang, J.-K. Liu of the State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, at the Chinese Academy of Sciences, Kunming, G.-Q. Shi, R. Fontaine and G. Zeng (CCDCP, Beijing). Fontaine is also based at the US Centers for Disease Control and Prevention in Atlanta, Georgia, Zhou at the South China Botanical Garden in Guangzhou.

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.