Since very early on in human history, people have relied on medicinal plants to cure them of their various ills. Ethnobotany is the study of plant lore and agricultural customs of a people and is progressively being explored by pharmacologists for the development of drugs. Given their extensive range of knowledge of medicinal plants, indigenous people have traditionally been the ultimate resource for retrieving this information for purposes of application to modern medicine–the medicinal value of plants is very significant–no more so than today. Tropical rainforests are particularly endowed with plants possessing curative properties. These richly biodiverse environments provide a veritable trove of flora containing compounds of medicinal value, which indigenous people have utilized and benefited from for centuries.
Through the rigorous gauntlet of natural selection, rainforest plant species have been perfecting various chemical defenses to ensure survival over millions of years of evolution, and are proving to be an increasingly valuable reservoir of compounds and extracts of substantial medicinal merit. These plants have synthesized compounds to protect against parasites, infections and herbivores, creating acutely powerful chemical templates with which pharmacologists can create new drugs. Approximately one half of the anti-cancer drugs developed sine the 1960s are derived from plants. Another hundred pharmaceuticals also have their origins in flora.
As tropical rainforests are especially abundant sources of medicinal plants, they provide countless renewable and restorative benefits to their inhabitants. There is an incredible amount of information contained within indigenous cultures, given their history and many lifetimes of exposure to plant life of the forest. It has been reported that people in Southeast Asia used up to 6500 plant species for medicinal use, while in the Northern Amazon, 1300 species were known to have been employed for the same purpose.
Kaiapo shaman in Brazil. Photo by Sue Wren
More than ever, researchers in pharmacology are looking to tropical rainforests to supply cures to all that ails humanity. The collision of eastern knowledge and western technology has resulted in a unique synthesis of medical belief and practice, along with the development and processing of innovative and effective drugs. The problem modern science faces in benefiting from this incredible wealth of material and information is the problem of access. Many of the traditional methods and general knowledge of medicinal flora is being lost to time. As healers, shamans and tribal elders age and die, their knowledge is dying with them. Scientists are searching for ways to preserve this knowledge to test it against contemporary diseases.
So far, researchers have been fairly successful in this endeavor. Seventy percent of the plants identified as having anti-cancer characteristics by the National Cancer Institute in the United States are found in tropical rainforests and 25 percent of the drugs used by Western medicine are derived from rainforest plants. And yet, despite all their promise, fewer than five percent of tropical forest plant species have been examined for their chemical compounds and medicinal value. This leaves great potential for even more discovery, but also the potential for great loss as rainforests are felled around the globe and unstudied species are lost to extinction.
When scientists do unearth a new plant species with the desirable qualities, it is rigorously analyzed to determine its chemical structure. After numerous tests and analysis, the isolated plant compound or extract goes into clinical trials for safety and effectiveness before getting final approval from the FDA, at least for distribution and use in the United States. Despite the laborious process of development and distribution, using rainforest species for derivation and synthesis of medicinal compounds is becoming a mainstream practice.
In 1983, there were no pharmaceutical firms from the United States involved in research of such plants, while today, well over 100 companies and government agencies are pursuing the study of rainforest plants for their medicinal potential. The 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 popular method involves selecting plants that display characteristics indicative of effecting animals, especially those that deter insects. Many chemicals toxic to insects show bio-activity in humans, which usually suggests pharmacological promise.
Commercial drugs that make it to market are typically very profitable, for example, the two chemicals derived from rosy periwinkle bring in annual revenues of $160 million. The drawback of these significant profits is the lack of distribution between accountable parties throughout the development process. Large companies usually benefit the most from such projects, while the local peoples and shamans get little in return for the original supply of their knowledge.
In the case of the highly lucrative rosy periwinkle chemicals, vincristine and vinblastine, essentially no money made it back to the country of origin, Madagascar.
Rosy periwinkle, photo by Julie Larsen Maher / WCS
Once the drug patent expired however, Madagascar was able to begin exporting tons of crude periwinkle and finally share in the profits of this remarkable plant.
This trend of exploitation without compensation is known as biopiracy. This unfortunate practice used to be the rule, but recent developments are indicative of change as companies are becoming more socially conscious and indigenous people are becoming more savvy. Drug companies are beginning to work within countries of origin to ensure conservation of habitat for valuable species. It is in the economic interest of both sides to collaborate in order to preserve the environment where these species reside.
A new procedure that is being explored by researchers to track and classify useful medicinal plant species may negate some of the issues surrounding the acquisition of knowledge, bypassing some of the controversy. This method involves a practice called “text-mining,” in which old botanical works are scoured for references to medicinal plants. One such work, the Ambonese Herbal, is a 17th century medical text compiled by Gregory Everhard Rumpf, “Rumphius,” a German botanist. Rumphius worked for the Dutch East India Company and was stationed in Ambon, an island located in the archipelago of present-day Indonesia. He began collecting, drawing and cataloguing plants in 1657, continuing his work even after going blind in 1670. After numerous personal tragedies, Rumphius died in 1702, but not before producing seven volumes of comprehensive botanical records.
The Ambonese Herbal explains the medical uses of almost 1300 native species of the Malay archipelago where Rumphius was stationed. The records are based on his questioning of local people on traditional healing treatments. In the text’s preface, Rumphius complains of delays, difficulties and deficiencies in shipments of medicine from Europe. Investigating and then using local remedies was far more practical than waiting months for the next boat to arrive.
Rumphius’s work is one of many historical texts that documents what is know as “ethnomedical” information. Traditionally, determining which plants to screen for medicinal potential involved ethnomedical study, in which shamans or healers were consulted to identify valuable species. In recent years, this approach has given way to high-throughput screening, in which thousands of random specimens are methodically tested by robotic technicians. Both methods have shortcomings however; the knowledge of indigenous peoples is dying with the older healers, and the mechanized processing of these fragile and often outdated texts is not free of errors.
Eric Buenz, a researcher at the Mayo Clinic College or Medicine in Rochester, Minnesota, has proposed a new, hybridized approach that combined the best aspects of both sources. His test would give access to the hundreds of medicinal texts dating from ancient Greece and on that sit unread and unstudied in libraries around the world. In reviewing these texts and comparing the information with modern medical databases, it should be possible to identify promising species as candidates for further analysis and testing.
Buenz and his colleagues analyzed the first volume of the Ambonese Herbal to test the new procedure. After translating the text into English from its original Dutch and Latin, two reviewers went through the volume and extracted all medical references. Afterwards, they drew up a table listing each species, the symptoms for which the plant was prescribed, and thus, its likely pharmacological function and abilities. This list of species was then checked against the International Plant Names Index database to identify misspellings and synonyms. Following this step, each species was looked up in NAPRALERT, a database listing all known biochemical and ethnomedical references to plants, to see if any had been mentioned previously in medical literature.
This method allowed researchers to determine the accuracy of the information in the Ambonese Herbal and identify species worthy of further investigation. Of the 42 plant species described in Rumphius’s first volume as possessing medical benefits, 24 had biochemical matches in NAPRALERT. Of the remaining 18, nine species had ethno medical matches, meaning their potential use as medicines was already known, but had not yet been by modern science and pharmacology.
The next step for Buenz and his team of researchers is to broaden and automate the process of cross-checking. Book scanners have become cheaper and more efficient in recent years, and yet are gentle enough to handle old and delicate texts. The project’s goal is to achieve high throughput with bioinformatics, or, using computers to collect, classify, store and analyze biochemical and biological information. With the use of natural-language processing software to search for specific expressions and cross-referencing potential matches with medical and botanical databases, the text can be processed quite rapidly. Going through the first volume manually took the researchers four weeks. Buenz’s experimental automated system completed the same task in only a few hours.
The biggest challenges with using this kind of technology are wrestling with foreign and antiquated languages, old typefaces and variations in terminology, but translation systems and databases are improving all the time. Other methods of drug discovery will never be fully replaced by text-mining, but isolating and extracting the accumulated medical expertise hidden away in old texts could be a helpful shortcut to determining the best plants for pharmacological use.
With this novel combination of indigenous and scientific foundations and methodologies, access to this valuable information is being afforded with much greater ease and success. The cures scientists seek are likely be found in tropical rainforests. Whether this knowledge is acquired through Buenz’s method of digital bioprospecting or passed on through oral histories from tribal elders, the benefit to medicine and to humans is apparent. Regardless of the means, the capacity of tropical rainforests to provide renewable and essential compounds only increase their value and necessity of protection and preservation.
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One of the most amazing aspects of tribal peoples is their boundless knowledge of medicinal plants, but even more remarkable is how they could have acquired such knowledge.