A multinational postmortem investigation has identified traces of the frog-derived toxin epibatidine in tissue samples from Alexei Navalny, and concluded that poisoning was “highly likely the cause of his death,” the scientists said in a joint statement at the Munich Security Conference. The Russian opposition leader died in prison on February 16, 2024. Laboratories in Germany, France, the Netherlands, Sweden and the UK took part in the analysis and accused Russian authorities of deliberately administering the substance.
Epibatidine is a potent alkaloid naturally present in the skin of certain Ecuadorian poison dart frogs, including Anthony’s dart frog (Epipedobates anthonyi) and the phantasmal dart frog (Epipedobates tricolor). Those species concentrate toxic compounds obtained from their insect prey in their bright skin as a predator deterrent; the phantasmal frog is listed as threatened by the IUCN. Although a number of amphibian toxins are known — for example the paralysis-inducing batrachotoxin — epibatidine-bearing frogs were not commonly reported as sources for hunting-dart poisons.
The compound was first isolated in the 1970s by American chemist John W. Daly, who obtained very small quantities from phantasmal frogs for study. Epibatidine drew pharmacological interest because of its powerful analgesic effects — roughly 200 times more potent than morphine — but development for medical use was abandoned because the margin between effective and lethal doses is extremely narrow. At toxic concentrations it can provoke seizures and paralyze the respiratory muscles, resulting in asphyxiation.
Investigators said it was improbable that large amounts of natural toxin from remote Ecuadorian frogs would have been transported to Russia. Instead, experts and former Russian scientists cited by the inquiry suggested the substance was likely synthesized in a laboratory. Vil Mirzayanov, a Russian analytical chemist who exposed Soviet-era chemical weapons programs, pointed to past work by Russia’s State Research Institute of Organic Chemistry and Technology (GosNIIOKhT) with natural toxins and agents such as ricin and fentanyl, and said Russia’s security services maintain advanced laboratories capable of producing and deploying such compounds.
Moscow has denied responsibility for Navalny’s death. The opposition leader was previously flown to Germany in 2020 after what Western laboratories identified as a nerve-agent poisoning; Russia rejected those accusations at the time. Navalny’s widow, Yulia Navalnaya, called the new findings “science-proven” evidence of murder and placed responsibility on President Vladimir Putin.
The five countries that conducted the epibatidine analysis have referred Russia to the Organisation for the Prohibition of Chemical Weapons (OPCW), alleging a breach of the Chemical Weapons Convention. Edited by: Jess Smee