Sidebar: Life from the Deadly
by John Tidwell
The Vodoun sorcerer finished praying and, with nose-plugs
still in place, poured the brownish mixture from his
mixing calabash into a small mason jar and handed it
to the young American squatting by the fire. The sorcerer’s
dark eyes twinkled as he watched Wade Davis turn the
jar in the first rays of dawn. This was it at last:
Zombi powder!
When Harvard ethnobotanist Wade Davis went to Haiti alone in 1982 and persuaded several Vodoun sorcerers to show him how to make a powder they said helped turn people into the “living dead,” he was not only hunting for a new kind of an anesthetic—he was also following a venerable tradition in Western science. Most of the time, plants and lower forms of life were the focus. But today bioprospectors are widening their scope to include the chemical weaponry of animals. “The new frontier for natural- product development right now is poisons,” says ethnobotanist Mark Plotkin. These come from such animals as Central and South American poison-dart frogs or from cone snails in the Philippines.
In recent years, biochemists have examined venoms from a huge variety of animal species from insects to amphibians and reptiles, seeking unique effects on the nervous and cardiovascular system. Whether for defense or hunting, millions of years of evolution have produced animal toxins to stop prey or predator quickly—and often permanently. Even more intriguing, many of these species have their own unique recipe, usually specific to the physiology of its target. According to University of Utah biochemist Baldomero Olivera, there are more than 500 species of marine cone snails in the Philippines, and each one uses a different configuration of deadly peptides (or short proteins) to catch fish. Other creatures, like John Daly’s poison-dart frogs, are thought to get their poisonous alkaloids, called batrachotoxins, from something they are eating (what that is remains a mystery).
Wade Davis discovered that the viscera of two tropical puffer-fish species, Diodon hysterix and Sphoeroides testudineaus, were a key ingredient in Haitian zombi powder. These fish are members of the family Tetradontiformes, which includes triggerfish, ocean sunfish, and porcupinefish, all known to sequester a deadly neurotoxin from a species of red algae. Like batrachotoxins, a pinhead-size amount can be lethal to human-size animals, and both kill by blocking nerve signals, causing paralysis and heart failure within seconds.
Although most compounds are still experimental, biochemists are able to turn these molecular swords into medical ploughshares, refining biological compounds into drugs that act to extend life rather than end it. A Canadian company called Thor Ventures wants to develop tetrodotoxin into a treatment for heroin addiction called Tetrodin. The poison of the five-inch giant Israeli scorpion (Leiurus quinquestratum), known as the “death stalker” throughout the Middle East, was found to contain a peptide called chlorotoxin, which targets cancerous glioma cells in the brain and stops them from spreading. The bite of the huge Cameroon red tarantula (Hysterocrates gigas) can immobilize prey as large as birds and small rodents. The toxin, which blocks calcium channels in nerves, is in preclinical development by Neurex, an American drug company, as a treatment for acute pain.
Olivera has discovered many venom peptides from cone snails that he has called conontoxins. These are currently the focus of clinical trials under the name Ziconotide, which is hoped to be non-addictive treatment for chronic pain. A team from the University of Melbourne led by Bruce Livett recently announced the patented discovery of one conotoxin, called ACV1. Early results suggest the potential painkiller may be 10,000 times more powerful than morphine, and some believe it is non-addictive.
Among other deadly bites, the toxin of the Colombian fer-de-lance viper was discovered to have anti-coagulant properties that could be used in stroke victims to prevent blood clots; the monacled cobra’s poison prevents immune cells from stripping myelin from nerve cells and could be used to treat multiple sclerosis. Even the dreaded Gila monster of the American Southwest has compounds in its venom that are being studied for the treatment of diabetes and other metabolic disorders.
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Very Special Toad
ZooGoer 31(5) 2002.
Copyright 2002 Friends of the National Zoo.
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