The Poisonous Potential of Muscarine in Mushrooms

Mushrooms display an incredible diversity in shapes, colors, and sizes. In autumn, many enthusiasts head into the woods to forage for tasty varieties, preparing them in various dishes. However, it's vital to identify poisonous mushrooms, as distinguishing them from safe options can be crucial for survival. But just how hazardous are these fungi?

A team from Friedrich Schiller University Jena and the Leibniz Institute for Natural Product Research and Infection Biology—Hans Knöll Institute (Leibniz-HKI) recently conducted research on this topic, unveiling their findings on muscarine in Angewandte Chemie International Edition.

Muscarine is a toxin found in several mushrooms, most notably in the fly agaric (Amanita muscaria), from which it derives its name. However, much higher levels of muscarine can be found in fiber cap and fool's funnel mushrooms.

Led by Dirk Hoffmeister, a professor at the University of Jena’s Institute of Pharmacy, the research revealed that muscarine exists not only in its toxic form but also as a harmless precursor that becomes dangerous when the mushrooms are damaged.

Initially discovered 150 years ago, muscarine has now been shown to be stored in the fool's funnel mushroom (Clitocybe rivulosa) as 4-phosphomuscarin, a less toxic variant. Sebastian Dorner, a doctoral researcher in Hoffmeister’s team, indicated that pure muscarine might have effects different from those observed in mushrooms containing it.

The fool's funnel mushroom, often mistaken for the edible champignon, releases its toxic muscarine only when it is damaged—whether through cutting, cooking, or digestion. In contrast, some mushrooms contain active muscarine right from the start. This combination of inactive and active forms of muscarine increases the risk associated with certain types of fungi.

Muscarine interferes with the action of the neurotransmitter acetylcholine, leading to symptoms such as excessive salivation, sweating, nausea, diarrhea, circulatory failure, and potentially fatal cardiac issues. Whether ingested as an active toxin or as an inactive precursor, accurately identifying edible mushrooms remains a critical factor for safe and enjoyable foraging.