Researchers Turn to Rain Forests for AIDS, Cancer Cures
Researchers at the New York Botanical Garden have turned to rain forest medicine men for help in their search for a medicinal plant that might yield a cure for AIDS.
Michael Balick and Douglas Daly, botanists at the garden’s Institute for Economic Botany in the Bronx, use the knowledge of South Americans and Central Americans to identify plant varieties that have seemed, over the generations, to have curative powers.
Balick and Daly collect samples from these plants and send them back to the National Cancer Institute in Bethesda, Md., where extracts from the samples are tested for effectiveness against AIDS and cancer.
The Institute of Economic Botany is one of three research groups chosen by the cancer institute to provide plant samples from the world’s rain forests. The University of Missouri has a contract for work in Africa and Madagascar; the University of Illinois has a contract for Asian rain forests.
The rain forest collection program is part of the cancer institute’s effort to extract medicines from natural substances. It also finances projects that collect marine organisms and fungi for testing against AIDS and cancer.
Since 1986, the Botanical Garden’s Institute of Economic Botany has been sending 1,500 plant samples a year to the cancer institute. Sifting through the 110,000 plant species that grow in the American tropics is no small task.
“Indigenous peoples have been looking at these plants for thousands of years,” Daly said. “It’s an ethno-botanical pre-screen. They know which plants have an effect on the human body. They can save us a lot of effort.”
The Amazon’s herbal healers have known for a long time that a tea made from artemisia leaves will kill internal parasites and that the root of the cockspur can be used for snakebite. They suggest the Spanish elder, with its sassafras-like odor, for curative baths.
Balick said the value of this pre-screening has been borne out by comparing samples collected at random to others collected with the help of a local healer. Of the 18 collected at random, only one plant showed activity against the AIDS virus. Of 20 species pre-screened by healers, five were active against the virus.
The focus on the rain forest as a source of medicines seems obvious. “Two thirds of the diversity of life is in the tropics,” Balick said, and more than 25% of prescription medicines today are derived from plants.
“Only 1,100 of the world’s 250,000 species of higher (seed-bearing or cone-bearing) plants have been thoroughly examined for medicinal potential,” Balick said. “That’s less than 1%.”
“The way we see it, plants have been experimenting with chemistry a lot longer than we have,” Daly said.
Tests on tropical plant samples at the cancer institute showed that the rain forest research may be on the right track. “We’ve seen some interesting activities from the so-called higher plants,” said Gordon Cragg, chief of the cancer institute’s natural products branch.
Of particular interest is Michellamine B, extracted from a vine that grows in Cameroon. Cragg said it has shown activity against the AIDS virus in lab tests.
Samples sent to the lab are soaked in water or alcohol to extract many of their natural chemicals. This extract is then applied to human cells formed in the lymph tissues infected with the AIDS virus. If the extract contains an effective anti-viral agent, it will protect the cells. Instead of dying, the cells will multiply.
The researchers must then determine which of the chemicals in the extract was protecting the lymphocyte cells and isolate that chemical. Then they can test the drug for toxicity on animals. If the drug passes the animal tests, the Food and Drug Administration will allow human clinical trials.
Animal toxicity studies have been started on Michellamine B, Cragg said. “If everything goes well--if it passes the toxicology and all that--I would imagine that it might be ready for clinical studies a year or two later.”
