Rooting for new antimicrobial drugs.

Scientists scouring the natural world for medicines have come up with another promising prospect. A compound isolated from the root of an African tree can kill fungi and bacteria, reports Kurt Hostettmann of the University of Lausanne in Switzerland. He and his colleagues are developing the chemical as a fungicide for treating infections and protecting crops.

The compound comes from the tree Bobgunnia madagascariensis, which grows throughout tropical Africa. Traditional medicine practitioners use the roots to treat leprosy and syphilis and also to kill termites. Knowing this, Hostettmann and his colleagues collected root samples to see if they could find any biologically active compounds.

A yellow substance coats the roots, appearing to protect the tree against fungi in the soil, Hostettmann says. The researchers tested extracts of the root bark, including the yellow substance, and other parts of the tree against various types of fungi and found that only the root-bark extract kills microbes.

Physicians are currently testing the compound, which is in the diterpene family, as a topical antifungal medication for people. If the compound becomes commercially viable, manufacturers could isolate it from cultivated trees. However, "for 50 grams of the compound, you must kill six trees," Hostettmann says. "We will probably be able to synthesize it."