Scientists believe they have found a potential antidote for a potent toxin found in the world’s most poisonous mushroom, the death cap.
The death cap mushroom, Amanita phalloides, is responsible for about 90% of mushroom-related deaths globally.
Its principal toxin is a peptide called α-Amanitin, a type of amatoxin which results in liver and kidney failure.
Chinese and Australian researchers have identified that indocyanine green, a dye currently approved in the US for use in medical imaging, appears to block the toxic effects of α-Amanitin.
The study’s corresponding author, Prof Qiaoping Wang of Sun Yat-Sen University in Guangzhou, China, said that previously no specific antidote existed for death caps “because we know little about how mushroom toxins kill cells”.
In tests in mice as well as human cell lines in the lab, the scientists found that indocyanine green was able to prevent liver and kidney damage that was induced by α-Amanitin. It also improved the probability of survival after poisoning.
“While the results are promising, further clinical experiments are needed to determine whether indocyanine green has similar effects in humans,” Wang said.
A fungi expert and the chief scientist at Sydney’s Royal Botanic Gardens, Prof Brett Summerell, who was not involved in the research, said death cap mushrooms were “extraordinarily dangerous and toxic” and were often mistaken for other mushrooms because of superficial similarities.
“The death cap can in the early growth stages resemble some of the straw mushrooms, which are … popular, particularly in a range of Asian cuisines,” Summerell said.
“In those early stages it can be quite difficult to differentiate the mushrooms,” he said. “It’s a white creamy colour. As they get a bit older you can start to get a greeny-yellow tinge to them in the death caps.”
“Death caps have an association with the roots of oak tree, so if you see something that’s under an oak tree, that’s really when you need to be careful and suspicious,” Summerell said.
While the toxins found in some other mushrooms can be degraded by heat, death cap toxins are “robust throughout cooking”, he added.
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“Mushroom poisoning is the main cause of mortality in food poisoning incidents worldwide,” the study’s authors note.
Αlpha-Amanitin exerts its toxic effects on cells by inhibiting specific enzymes required for protein production. To work, the toxin relies on a protein in the body called STT3B. Indocyanine green appears to work by inhibiting the function of STT3B.
The researchers found beneficial effects in mice treated with indocyanine green four hours after poisoning with α-Amanitin, but not in mice treated only eight or 12 hours after they were exposed to the toxin.
“This may be because [α-Amanitin] has caused irreversible damage … which is unable to be salvaged,” the researchers concluded. “This suggests that [indocyanine green] should be given as early as possible during treatment.”
The research was published in the journal Nature Communications.