Around 170 species of poison arrow frogs exist in the rainforests of South America, from which 400 toxins have been extracted and classified today. The frogs range from bright blue to startling yellow in colour, and one species has shot to scientific prominence since the isolation of its skin toxin 1974. The tiny red frog smaller than a fingernail may provide an invaluable implement in the modern medical toolkit in coming years.

What's in a frog?

Equadorian poison arrow frog

  Epibatidine, chemical name (chloropyridyl)-azabicycloheptane, is a toxin derived from the skin of the equadorian poison tree frog, Epipedobates Tricolor, and named in the honour of the frog. The frogs are red and green stripped, and the toxin they produce was used by the frogs themselves against predators, and also by native Indians to tip their arrows. The frogs were so toxic, arrow tips only had to be rubbed across the back of a frog to coat them with poison.
  The poison's toxicity causes paralysis even in the minute doses secreted by the frog and a dose of just 2 miligram can kill a person.

Biosynthesis of Epibatidine does not occur in the frog, and amazingly, the frogs are not affected by the poison. Over millions of years, the frogs have evolved to become resistant and use it to their advantage.

Why is epibatidine so important?

 Other than for coating the arrowheads of natives and causing their enemies to suffer a convulsive, paralysed, albeit painless death, it was discovered that the toxin also held potent analgesic (painkilling) effects, surpassing even opioids such as morphine.
  Most painkillers operate via the same pathway as morphine, and act on opioid receptors, whereas epibatidine has a similar structure to nicotine, and compete with nicotine receptors. This sparked interest, and research followed to derive non-toxic compounds with the same effect. Current research is concentrating on ABT-594, a promising analogue.
   Epibatidine is a alkaloid (nitrogen containing compound) consisting of 2 ring structures. The compound is displayed on the right.

For more on synthetic routes for epibatidine and derivatives, click here.

Molecule needs at least Java 1.2
3D model of Epibatidine

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