Image: DAVID R. PARKS
From the plant-choked jungles of Malaysia to the coral reefs of the Caribbean, scientists are combing the planet for cures to our most intractable maladies. Such bioprospecting is tedious work¿on average only one in thousands of natural compounds tested shows pharmaceutical promise, and only a handful of those ever make it to market. Yet despite the high risk of failure, researchers press on, driven by the realization that with millions of years of experience under her belt, Nature is the ultimate chemist.
Indeed, nearly half of all human pharmaceuticals now in use were originally derived from natural sources. Perhaps the most famous example is aspirin, which evolved from a compound found in the bark and leaves of the willow tree and was later marketed by Bayer starting in 1899. Some 50 years later, scientists identified anticancer compounds in the rosy periwinkle (right), which pharmaceutical heavyweight Eli Lilly subsequently produced for the treatment of leukemia and Hodgkin¿s disease. Other well-known examples include the cancer-fighting Taxol, isolated from the Pacific yew tree, and Aggrastat, an anticoagulant based on the venom of the saw-scaled viper from Africa.
Today many other compounds taken from Nature's medicine cabinet are showing promise (see sidebar). And with thousands of species as yet untapped for their chemical potions, it's tempting to compare bioprospectors to the proverbial kids in a candy store. But in fact, those sweet rewards sometimes come at tremendous cost. Researchers are increasingly finding themselves at odds with traditional healers in many parts of the world, who have long made use of plants and animals to treat various ailments, and with Nature herself, who does not typically part with anything without ecological consequences.
That there is a need for new drugs to combat AIDS, Alzheimer's and other ailments, however, goes without saying. In addition, researchers are under mounting pressure to find compounds to replace those that have become less effective. With bacterial resistance on the rise, for example, the world desperately needs new antibiotics. The same holds true for cancer drugs, which can lose their potency in a patient over time. And Nature may still be the best place to hunt for such lifesaving compounds.
With about 10 million species inhabiting the earth, how do scientists determine which ones contain potential panaceas? In many cases they are screening randomly¿a process that yields on average one useful drug for every 20,000 samples analyzed. But other researchers employ a different strategy, consulting indigenous people when possible. According to Conservation International, studies have shown that plants identified by locals are in fact up to 60 percent more likely to have pharmaceutical potential than their randomly collected counterparts.
Recently plants and sessile or slow-moving marine invertebrates such as sponges, corals and sea slugs have attracted particular attention because for these organisms, running away from a predator is not an option. Instead they have chemical defenses. And with a little tweaking, the potent toxins they produce¿as well as those manufactured by certain poisonous snakes, frogs and land invertebrates¿can actually save lives.