Saving What Remains

MEDICINAL PLANTS

July 22, 2007



Plants have broader uses than as just food and a genetic reservoir. Increasingly, rainforest plants and to a lesser extent, rainforest animals, are the source of compounds useful for medicinal purposes. The rainforest has been called the ultimate chemical laboratory with each rainforest species experimenting with various chemical defenses ensure survival in the harsh, world of natural selection. They have been synthesizing these compounds for millions of years to protect against predators, infection, pests, and disease. This makes rainforest species an excellent reservoir of medicines and chemical templates with which researchers can create new drugs.

Rainforest plants have already provided tangible evidence of their potential with remedies to all sorts of medical problems from childhood leukemia to toothaches. 70% of the plants identified as having anti-cancer characteristics by the US National Cancer Institute are found only in the tropical rainforest. Some examples of plants, which are responsible for 25% of the drugs used by Western medicine, that have been used for drugs, are included in this table.

Despite all their promise, as of the mid-1990s fewer than 5% of tropical forest plant species (and 0.1% of animal species) had been examined for their chemical compounds and medicinal value. Once a plant with the desired qualities is discovered, it is rigorously analyzed for its chemical structure, then going clinical trials for effectiveness and safety before getting final approval from the US FDA. Nevertheless, using rainforest species for derivation and synthesis of medicinal compounds is becoming a mainstream process. In 1983 there were no U.S. pharmaceutical firms involved in research of such plants. By the mid-1990s there were well over 100 corporations and U.S. government agencies are studying rainforest plants for their medicinal capacities.

One such organization, the U.S. National Cancer Institute maintains screening of rainforest species for anti-cancer and anti-HIV effects. Because there are so many plant species, institute researchers concentrate on close relatives of plants already known to produce useful compounds. Another method is to choose plants that display characteristics indicating they have an effect on animals, like preventing deterring insect pests. Many chemicals toxic to insects show bio-activity in humans meaning they may have drug promise.

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Rainforest plants have long been recognized for their potential to provide healing compounds. Indigenous peoples of the rainforest have used medicinal plants for treating a wide variety of health conditions while western pharmacologists have derived a number of drugs from such plants. However, as forests around the world continue to fall -- the Amazon alone has lost more than 200,000 miles of forest since the 1970s -- there is a real risk that pharmaceutically-useful plants will disappear before they are examined for their chemical properties. Increasingly, it is becoming a race against time to collect and screen plants before their native habitats are destroyed. One near miss occurred recently with a compound that has shown significant anti-HIV effects,

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Indigenous uses of plants can also offer hints of potentially useful plants. For thousands of years, Indigenous groups have extensively used rainforest plants for their health needs. They have experimented with a wide range of plants. The peoples of Southeast Asian forests used 6,500 species, while Northwest Amazonian forest dwellers used at least 1300 species for medicinal purposes. The success rate for discovering medicinal plants from traditional use is high because rainforest peoples, notably shamans, have been experimenting with various combinations and dosages for generations. A recent study in Samoa found that 86% of the plants used by local healers yielded biological activity in humans.

The National Cancer Institute can rapidly screen compounds for activity against 60 cancer types. When the compound shows promise, chemists isolate the molecules responsible for the activity and then compare the molecular structure with that of known chemicals. Sometimes the molecule already has been identified, but is not used medicinally; at other times the molecule will be altered to produce the desired action. If the molecule has potential as a drug, it is tested for certain characteristics including safety, effectiveness, and side effects. If it passes those tests, a corporation or government agency must finance bringing the drug to market—a process that costs more than $800 million and may take 12 years. Before reaching the public market, the drug must go through rigorous clinical trials. According to the Global Bioscience Development Institute, for every 10,000 to 20,000 compounds screened for possible activity in the basic research stage, about 250 make it as far as pre-clinical testing. Of those, five drug candidates make it as far as clinical trials, and only one becomes an actual FDA-approved drug. Thus the process of bringing a rainforest drug, or any, pharmaceutical product to market is long and costly.

Nevertheless, commercial sales from such drugs typically take in huge sums: the two chemicals derived from rosy periwinkle bring in revenues of US$160 million per year. Large companies usually benefit the most from such projects while the local peoples and shamans get little in return. For example, virtually no money from vincristine and vinblastine derived from the rosy periwinkle made it back to the country of origin, Madagascar. However, once the drug patent expired, Madagascar was able to begin exporting tons of crude periwinkle annually.

In the past such exploitation, known as biopiracy, was the rule. While drug companies raked in millions in revenue, the community that found the plant producing the drug was left with token baseball hats, beads, or aspirin as compensation. One of the biggest biopiracy coups occurred last century when the British smuggled (at least Brazilians allege) rubber tree seeds out of Brazil to their colony of Malaysia, ending the lucrative Amazonian monopoly on rubber.

Recently a bitter patent battle has erupted between the Inter-American Foundations, a US development agency, and COICA, an organizations representing Indigenous peoples from the Amazon region, over Ayahuasca or yag. Yag is the celebrated hallucinogenic, derived from a rainforest liana and other plants, which is used ceremonially by Amazonians. The biopiracy incident was initiated in 1986 when an American visiting Ecuador took a sample of yag without permission and acquired a patent from the US government. Today the American has started the International Plant Medicine Corporation and working with yag to develop psychiatric and cardiac pharmaceuticals. COICA says the American has no right to patent, without permission, a plant compound that has been used for generations by Indigenous peoples. Complicating the debate, is the refusal of the US Senate to ratify the UN Convention on Biodiversity, which has been ratified by more than 100 countries including Ecuador, where the Yag sample was acquired. The UN agreement includes the recognition of intellectual property rights of Indigenous peoples.

This exploitation without compensation has been the trend, although today, more of the revenues are returned to the Indigenous peoples. Most tropical countries are ill-suited for the analysis of species for medicinal value and lack the funds to sponsor such activities so drug research and development will likely continue to be dominated by industrialized countries. However compensation for the country of the product's origin must be addressed if the source of these products -- the tropical rainforest—is to be preserved.

Several pharmaceutical companies have agreed to share revenues with local people. The drug Prostialin, isolated in 1984 from a Samoan rainforest tree, has exhibited strong activity against HIV in tests. With its discovery, the National Cancer Institute has guaranteed that part of the royalties from the sale of the drug will be returned to the Samoans. As a result the fiftieth national park of Samoa has been established to encourage local healers to use medicinal plants a in sustainable way, in order to pass their knowledge on to the next generation. Similarly, in 1991, Merck and Company recently invested $1 million in Costa Rica's INBIO project to assist in the cataloging and screening effort. The institute will collect and identify organisms, sending samples from the most promising species to Merck laboratories for medicinal assay. If the compounds prove useful and the resulting drugs make it to market, the Costa Rican government is guaranteed some of the royalties, which will be set aside for conservation projects. A similar agreement is in the works between Bristol-Myers Squibb and the government of Suriname.

Kratom leaves being dried. Photo by Rhett A. Butler

Review questions:

  • Why are plants a good source for medicines?
  • What is biopiracy?

Continued: Medicinal plants (continued)