Nature's Pharmacy: Ancient Knowledge, Modern Medicine

Really Wild Remedies

Nearby, in Tanzania's Mahale Mountains National Park, a lethargic chimpanzee suffering from diarrhea and malaise slowly pulls a young shoot off a small tree called Vernonia amygdalina. She peels away the shoot's bark and leaves with her teeth, and begins chewing on the succulent pith. Swallowing the juice, she spits out most of the fibers, then continues to chew and swallow a few more stalks for half an hour.

Recovered within 24 hours, both of these females resume business as usual. They were both suffering the effects of an intestinal parasite infection. And, in case you haven't guessed, they both ate from the same tree.

Zoopharmacognosy
Back by popular demand, the revival of herbal medicine among industrialized nations is challenging the modern pharmacological market while captivating the interest of scientists in numerous fields. Tired, perhaps, of expensive, highly synthetic drugs, we look to traditional healers in faraway places to share their time-tested therapies. The majority of the world's population, in fact, still relies on traditional medicines to some degree for their basic health care. Some scientists feel this is a valid method of finding cures for certain diseases. Others believe we should head straight for the jungle and see what leafy remedies animals are munching on. After all, isn't it possible that people learned about self-healing by watching their wild neighbors? "The probability that animals may have something to teach us about the medicinal use of plants is quite high," says primatologist Michael Huffman at the Kyoto University of Japan. Actually, the idea's hardly been ignored. In fact, an entirely new field, sometimes called "zoopharmacognosy," has evolved from the onslaught of diverse research on self-medicative behavior in animals over the past two decades. Animal behavorists, ecologists, pharmacologists, anthrophologists, geochemists, and parasitologists have all contributed to this truly multi-faceted discipline.

Huffman is one of the pioneers of zoopharmacognosy, thanks to his observations in 1987 of an animal -the chimp described earlier- attempting to heal herself. Intrigued by her speedy recovery and curious about the cause of her illness, Huffman analyzed the chimp's dung and found the intestinal parasite Oesophagostomum stephanostomumto be the most likely explanation for her symptoms. What's more, he found lower levels of the worm in another female chimp's excretions 20 hours after she ate the bitter pith from a Vernonia tree. This prompted him to collaborate with researchers in Japan, Canada, France and the United Kingdom to find out what, if anything, the plant contained that might have killed the worms.

Huffman and his colleagues made an important discovery: They isolated an entirely new class of compounds from the pith, one of which, vernonioside B1, was found to possess antiparasitic, antitumor, and antibacterial properties. What's more, the leaves contain high levels of a well-known class of poisonous compounds found only in minute amounts in the pith. While these substances are also antiparasitic, they are likely toxic to the chimps. Vernonia amygdalinais not a regular part of the chimpanzee diet, and when it is eaten, it's often in small amounts, by chimps that appear ill. For these resons, Huffman believes that they consume the plant for its medicinal rather than nutritional benefits. His work was the first to verify illness in an animal that showed improvement after eating a known medicinal plant. Interestingly, Vernonia amygdalinahas more than 25 known medicinal uses among people of sub-Saharan Africa, about half of them for intestinal and parasitic ailments. People have learned to use the pith, leaves, and roots, probably because the more toxic compounds have been selectively bred out of the Vernonia that is cultivated in gardens.

Reproductive Remedies.
Animals may have "stumbled" upon a wealth of ways to control reproduction, and scientists believe recent discoveries are only the tip of the iceberg. According to World Wildlife Fund scientist Holly Dublin, African elephants (Loxodanta africana)seek a particular species of tree, possibly to induce labor. Dublin followed a pregnant elephant for more than a year in East Africa, and observed that the elephant followed a strictly uniform diet and pattern of daily behavior until near the end of gestation. At that time, the elephant walked 17 miles in one day -many more than her usual three- and ate a tree of the Boraginaceae family from leaves to trunk! Four days later she gave birth to a healthy calf. Dublin found that Kenyan women brew tea from the leaves of this tree to induce labor. She believes this is more than just coincidence, as does University of Wisconsin anthropologist Karen Strier about her own research. Stier found that, at different times, muriqui monkeys (Brachyteles arachnoides)of Brazil go out of their way to eat leaves of Apulia leiocarpaand Platypodium elegans,and the fruit of Enterlobium contortisiliquim(monkeys ear). The first two plants contain isoflavanoids which are componds similar to estrogen. Ingesting the leaves may increase estrogen levels in the body, thereby decreasing fertility. Alternatively, eating monkey's ear may increase the monkey's chances of becoming pregnant because the plant contains a precursor to progesterone (the "pregnancy hormone") called stigmasterol.

Self-medication in animals remains a field with endless unexplored avenues. The highly debated subject prompts questions such as "Do animals really know how to cure their own ailments?" and "How did this behavior begin?" Washington University biologist Jane Phillips-Conroy, who studied self-medication in baboons, says, "Just because a monkey eats a particular plant doesn't mean he knows it's medicinal. We need more definitive studies like those of Huffman, with actual proof that particular plants are effective against particular illnesses."

Scientists agree that understanding the process of self-medication in animals has many important implications for humans. Huffman emphasizes the tangible benefits and need for conserving the habitats in which medicinal plants flourish along with the animals that use them. "Some are interested in just finding new patentable chemical compounds [for use in human medicines], but that's only one part of it," he comments. "These animals live in an environment where they're faced every season with the threat of reinfection by parasites. They may have found ways to control these infections without creating resistance to the chemicals or other means they use, and we have much to learn about how they do this."

Further exploration in the field of zoopharmacognosy would teach us more about behavior, botany, and medicine, all areas in which we may apply our knowledge to benefit future generations - but without wildlife or habitats, there will be little to study. According to Huffman, "With growing chemoresistance to the Western world's current arsenal of antibiotics and anthelmintics [antiparasitics], we cannot afford to let that potential source of knowledge disappear."

Reprinted by kind permission of ZooGoer 27(1) 1998. Copyright 1998 Friends of the National Zoo. All rights reserved. "Http://www.fomz.org/zoogoer/zg1998/27(1)remedy.htm"

African Elephants courtesy of Michael Bright. Intelligence in Animals.U.S.A.:The Reader's Digest Association, Inc., 1997.

Mother and baby chimpanzees courtesy of Susan McGrath. How Animals Talk.National Geographic Society, 1987. pp.30-1.