Scientists are studying a bizarre menagerie of creatures including frogs, toads, snakes, flies, leeches and sharks in the search for new medicines.

Chemicals found in their bodies may help treat a range of human ailments, including high blood pressure, difficult to cure infections and even cancer, they believe.The idea of tapping nature for pharmaceuticals is not new. A quarter of Western prescription drugs are based on plant-derived substances and five of the world's top 30 drugs come from fungi.

But now the "bio-prospecting" net is being cast wider.

According to speakers at a "Drugs from Nature" conference here, the potential of the animal kingdom is huge.

Amphibians alone produce an "awe-inspiring" number and diversity of compounds in glands on their skin, said Dr. Barry Clarke of London's Natural History Museum.

He believes chemicals from frogs and toads may have particular value in treating skin and respiratory infections.

Special interest is centered on how certain creatures with only a rudimentary immune system manage to survive in a hostile environment, teeming with pathogenic bacteria and fungi.

The key appears to be the production of a series of complex molecules called peptides, which provide a potent defense system against potentially lethal microbes.

Peptides isolated from the African clawed toad, called magainins, are already being tested in the United States by Magainin Pharmaceuticals.

Scientists at Tokyo University are working on a peptide called sapecin found in the blood-like substance, hemolymph, in fly larvae. Sapecin appears to be a powerful antibiotic which protects young maggots from which the billions of bacteria which swarm in their natural habitat-- rotten meat.

Sharks, too, may have an in-built anti-microbial system, this time based on a novel steroid compound called squalamine which appears to protect them from infection.

In some disease areas, animal-based drugs have already arrived.

ACE inhibitors, a new class of heart drugs, were originally derived from the venom of the Brazilian pit viper. Drug designers have refined the original product and synthesized a version that could be given by mouth.

The first such oral ACE inhibitor, marketed by Bristol-Meyers Squibb as Capoten, has been on the market since 1981, and last year it racked up global sales of $1.8 billion.

View Comments

Other venoms may also prove of medicinal value, Professor Eugene Grishin of the Russian Academy of Sciences believes, since they affect a host of cellular systems. And the chemical venom pool is immense, with 20 different toxins isolated from just one species of scorpion.

One creature with a long history of medical use which may be about to make a comeback is the leech.

Used for centuries for blood-letting and the removal of "diseased blood," the leech contains a variety of chemicals in its saliva which stop blood from clotting.

Ciba-Geigy has now developed a genetically-engineered version of one of these compounds, hirudin, which pharmaceutical analysts expect to reach the market in 1996.

Join the Conversation
Looking for comments?
Find comments in their new home! Click the buttons at the top or within the article to view them — or use the button below for quick access.