12.3 Earthly Goods Rain Forest Medicine


For millions of years, rainforests have girdled the globe. Some of them are incredibly ancient: Remnant rainforests in northeastern Australia are more than 100 million years old. They are the deep reservoirs of life on this planet and are homes to half of the world's species. In them, 99% of the biomass consists of plants. Early European naturalists recognized the potential for new products contained in this abundant ecosystem.

The rainforests are biodiversity run amok. The largest rainforest in the world is in South America and is traversed by the largest river in the world, the Amazon. A forest without equal, the Amazon teems with more varieties of plants and animals than any other place on earth. Plant life is stunningly diverse: One of every four plants on earth grows in Amazonia (the basin of the Amazon river). Three factors influence diversity: the amount of solar energy--abundant at the equator; climate stability--no harsh seasons such as we have here, and sheer size--the bigger the habitat, the more the diversity. Habitat size is suffering from human intrusion: Tropical logging is destroying the world's rainforests at an astonishing rate.

Rain forest destruction proceeds at a rapid pace. Logging and conversions to cattle ranching are among the most immediate reasons. For many Third World countries, their ancient rainforests are a source of short term income. Indigenous peoples who have lived in them for centuries see their surroundings as food, medicine, spirituality, and shelter. Debt-burdened governments see the forests as a one-time quick source of cash earning export products.

Each year, an area about the size of Indiana is deforested. In forty years, much of it will be gone. With that loss, the biodiversity is forever lost. One current estimate is the species are being lost at the rate of a species every four hours.

A majority of the world's insects live in the Amazon rain forest, Why hasn't this insect horde destroyed all of the forest greenery? The answer explains the importance of rainforest plants to modern medicine.



Plants protect themselves by producing an astonishing array of chemicals that are toxic to insects, thereby deterring predation. When ingested by humans, these same plants--and their chemical weapons--may act in a variety of ways on the body: they may be nutritious, poisonous, or even hallucinogenic. In some cases, they are therapeutic. One of the most valuable commodities from the rainforest is cure for human disease.

Of special interest in this discussion are secondary metabolites produced by plants. Chemically, you would recognize them as alkaloids, terpenes, steroids, flavonoids, tannins, and so on. Amongst these are substances that kill viruses, block cancer, combat neurological disease, combat depression or stroke, and even lower blood serum cholesterol. The study of natural drugs and their chemical constituents is called pharmacognosy. Be sure to learn this term!



Stories of poison tipped arrows soon reached Europe after Columbus's second expedition in 1493. Horrifying accounts of death and paralysis attracted enormous interest.

Blowguns are fashioned from the 'blowgun tree', a member of the nutmeg family. A long branch is selected, split in half, the center is reamed out, and is reassembled with a resin and tightly wrapped with roots from the philodendron tree. The slender darts are made from palm leaf stalks and are sharpened with pirahana teeth. The 'business end' is dipped in curare mixtures or dart poison.

The arrow is discharged with a sharp puff of air; a skilled user can hit a small monkey at 90 feet. Blowguns were used by Indians in the southeastern United States, but they did not have such a rich pharmacopeia at their disposal.



Chemicals from plants that have medicinal value are called phytochemicals. The largest group amongst these chemicals are the alkaloids, compound that always contain a nitrogen atom and which in pH are bases. A single plant may contain fifty alkaloids. These include caffeine, nicotene, and cocaine. Alkaloids are secondary compounds (secondary compounds appear not to be necessary for a plant's essential functions) and appear in 45% of tropical plants. The use of alkaloids is very ancient. They can be identified by their bitter taste. One of these is curare which we will discuss shortly. Indians in Columbia derived curare from the skin of frogs.

A famous alkaloid is opium, derived from the poppy plant. Its principal ingredient is morphium; now known as morphine.



Bark from the Cinchona tree was an ancient Andes Indian treatment for 'intermittent fevers.' Legend says they learned about it from jaguars who cured fevers by gnawing on the bark of the quina tree. The Inca made a tea from the bark. Quinine derived from that bark was the first big success in the search for medicinals from tropical plants.

By 1820, two Frenchman isolated quinine, and the rush was on. Harvesting in South America soon (no pun intended) outstripped the bark supply. Seeds were secretly taken from South America. British botanists failed to make them grow, but Dutch growers had better success. They transplanted the best of the cinchona trees to Java and quickly created a monopoly which lasted until World War II. Early in that war, seeds and cuttings were returned to the Americas to be later harvested and used by the Allies.

In 1944, quinine was synthesized in the laboratory, leading to more synthetic quinine alternatives. In recent times, malaria plasmodium have become resistant to many of the synthetics, and there has been a return to the original naturally produced quinine which is in fact a combination of closely related chemical substances.

Quinine changed history: It enabled Europeans to colonize malaria infested equatorial areas around the world when prescribed prophylactically as a preventive.



Amazonian indigenous peoples refused to reveal the manufacture of curare or acknowledge its source. By the 1930s, botanists had narrowed the search to a handful of plants, but were still stuck with just a gooey black paste that had the power to paralyze so perfectly. The secret was unveiled by an American, Richard Gill--a medical school dropout. His story is one of adventure and loss of his discovery to others.

Gill risked everything to find the secret of curare. He claimed success in 1938. The son of a physician, he quit his own medical education and headed for South America. He sought the chemical basis of curare as a treatment for Parkinson's disease and multiple sclerosis.

Why? What were his reasons? Nerves transmit messages from one nerve cell to another, or nerve cell to muscle cells by special chemicals called neurotransmitters. Curare works by blocking the receptor sites for these chemicals. Thus, the nerves send the message but the muscles cannot receive them. He reasoned that a drug such as curare would be helpful in the treatment of multiple sclerosis.

In one of those strange twists of fate, Gill himself was diagnosed with multiple sclerosis. While disabling him to a degree, it intensified his efforts to learn the chemical basis of curare. Gill learned the Quich language and culture. He learned the ingredients of the complex 'brew' of curare used by Indians, and finally identified the active ingredient as from the Chondodendron family of plants. Back in the United States, the reaction of the large pharmaceutical firms was cautious.

Trials on patients with spastic paralysis only gave momentary relief, not a cure. It was tried on a nine-year-old boy with spastic paralysis. The boy's arms and legs were drawn up in a rigid contortion, useless and immobile. Within minutes of being injected with curare, the boy's limbs became flaccid and flexible. But, when it wore off, they contracted again. Relief was only fleeting.

Now, in another twist of fate, Gill's discovery was appropriated by others. Curare was tried (successfully) in controlling convulsions in electroshock therapy. From this, in 1942, it was tried (with stunning success) to provide complete muscular relaxation with general anaesthesia. The major drug companies were now interested and Gill was quickly brushed aside, to be just a footnote in the history of curare. He died in 1938.



The rubber tree, native to the Amazon, was first discovered and used by the local Indians. Not only did they eat the seeds, but they dipped their feet in the latex and dried them over the fire, thus creating the first custom-made sneakers.

Latex is produced naturally by Hevea as a defense against insects. When they invade the bark, the latex immobilizes their mandibles and kills them.

All major industrial attempts to use the latex failed until Charles Goodyear discovered the vulcanization process in 1839.

As a result of the discovery of vulcanization, the demand for rubber rose astronomically--from thirty-one tons in 1827 to twenty-six hundred tons in 1857. Amazonia was supplying the rubber for most of the world's car tires by the turn of the century, and soon rubber was running a close second to coffee as Brazil's main source of currency.

(My note: Coffee has a convoluted history, too. Coffee is native to Ethiopia, in Africa where natives chewed the leaves and ate the fruit--to pep them up and blunt their hunger pangs. The Arabs invented the brewing process and it spread throughout the Islamic world. Coffee was brought to Europe by the Dutch. A single bush made its way to a royal hothouse in Paris; from there, it was smuggled into South America in a floral bouquet. Thus, Brazil got its coffee plants as England got its rubber trees . . . but that is getting ahead of our story.)

Latex rubber brought wealth to Manaus in Brazil and Iquitos in Peru. The rubber barons in Manaus built a European style city, complete with a lavish opera house. Fashionable well-to-do shipped their dirty laundry to Paris. An enterprising British botanist ended it all by shipping ripe rubber tree fruit (with seeds) past unsuspecting customs officials. Only a few of the seeds germinated, but enough did to establish rubber plantations in British colonies of South East Asia. Trees selected for the best characteristics planted in neat, straight rows to facilitate production quickly garnered the world market.



Steroid hormone manufacture has its origins in the study of Aztec medicines. Successful manufacture of these compounds was initially from yams, a relative of the sweet potato. Mexico became the foundation and world leader in the steroid market until its government tried to nationalize production--and forced the industry out of the country. It was to be a chemical version of OPEC, but it ignored the resourcefulness of the pharmaceutical industry. They came up with alternatives, and the free market left Mexico a minor player in the diosgenin-based steroid industry.



Another serendipity in the drug saga from the rainforest involves the rosy periwinkle from Madagascar. Initially a diabetes treatment in Jamaica, Ely Lilly researchers discovered that it killed cancer cells. Alakaloids from the plant, also known as Vinca, became fabulously successful cancer drugs called vincristine and viblastine. They turned childhood leukemia and Hodgkin's disease from also sure killers to among the most treatable and least lethal of all cancers--and made Lilly lots of money. People in Madagascar got nothing: genetic property rights remain a contentious issue.

..... CJ '99


Duke and Vasquez Amazonian Ethnobotanical Dictionary Boca Raton: CRC Press, 1994.

Joyce, C. Earthly Goods Medicine Hunting in the Rainforest New York: Little Brown and Company, 1994.

Plotkin, M. Tales of a Shaman's Apprentice New York: Penguin Group, 1993.