A toxin produced by certain Ecuadorian poison dart frogs has been identified as the likely cause of Alexei Navalny’s death in prison, according to a multinational postmortem. Scientists from Germany, France, the Netherlands, Sweden and the UK analyzed tissue samples from the Russian opposition leader, who died on February 16, 2024, and said traces of the chemical epibatidine were found. In a joint statement at the Munich Security Conference they said poisoning was “highly likely the cause of his death” and accused Russia of deliberately administering the substance.
Epibatidine is a potent alkaloid found in the skin of some dart frogs native to the Ecuadorian foothills, including Anthony’s dart frog (Epipedobates anthonyi) and the phantasmal dart frog (Epipedobates tricolor). The phantasmal frog is listed as threatened by the International Union for Conservation of Nature. These frogs accumulate toxic alkaloids from their insect prey and concentrate them in their brightly colored skin as a defense against predators. While many amphibian toxins exist — such as the paralysis-inducing batrachotoxin — epibatidine-bearing species were not historically used to tip hunting darts in the way some other frogs were.
Epibatidine was first isolated in the 1970s by American chemist John W. Daly, who extracted under a milligram from phantasmal frogs for analysis. The compound attracted pharmacological interest because of its powerful analgesic effects; it is approximately 200 times more potent than morphine. However, epibatidine’s therapeutic use was abandoned because its window between effective and lethal doses is very narrow. At toxic levels it can trigger seizures and paralyze the respiratory muscles, causing asphyxiation.
Given the frogs’ remote South American habitat, investigators consider it unlikely that bulk quantities of natural toxin would have been transported to Russia. Instead, experts and former Russian scientists say the substance was probably synthesized in a laboratory. Vil Mirzayanov, a Russian analytical chemist who exposed Soviet-era chemical weapons programs, noted that Russia’s State Research Institute of Organic Chemistry and Technology (GosNIIOKhT) has previously worked with natural toxins and agents such as ricin and fentanyl. Mirzayanov and others said Russia’s security services, which maintain advanced laboratories, would be capable of synthesizing and administering such a poison.
Russia has denied responsibility for Navalny’s death. The opposition leader had been flown to Germany in 2020 after what Western labs called nerve-agent poisoning; Moscow denied involvement at that time as well. Navalny’s widow, Yulia Navalnaya, called the new findings “science-proven” evidence of murder and said President Vladimir Putin was responsible.
The five countries that conducted the analysis have referred Russia to the Organisation for the Prohibition of Chemical Weapons (OPCW) for breaching the Chemical Weapons Convention. Edited by: Jess Smee