Medicinal Effects of Plants

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As our hunter-gatherer ancestors searched for edible foods, they discovered plants that produced unusual effects on their minds and bodies. In time, they learned to identify and use these plants to treat specific illnesses, to stimulate their minds, and to produce hallucinations. Each generation, the knowledge was refined and then passed on to the next generation. Hunter-gatherer societies that still exist today often use several hundred plants to treat illnesses and to alter the mind.

aeValleha We now know that the active ingredients in medicinal plants evolved as chemical defenses against herbivores, especially insects. As many as 100,000 such molecules exist. These unusual molecules, evolved to alter the bodies of insects, have profound effects on human bodies as well. Consider aspirin, a miracle drug used for the treatment of pain, fever, inflammation, and headaches. Salicin, a molecule similar to aspirin, occurs naturally in the leaves of myrtle (a Mediterranean bush), the leaves and bark of willow trees, the oil of winter-green, and several other plants. We have evidence, in the form of written prescriptions found in Egypt, that myrIle leaves were used to treat uterine pains as many as 3.500 years ago. Hip pocrates, of ancient Greece. prescribed myrtle leaves to reduce fever.

 Later, in wc. 30. the Romans used wile:, low leaves to treat inflammation. in the Middle Ages. a derivative of sailor.' was used to treat headaches. We still use salicin, in the form of aspirin, to treat pains, fever, inflammation, and headaches. Consider another example—digitalis, a drug that strengthens heart contractions and synchronizes the beat. In t785. a British physician reported that ingestion of dried leaves from the foxglove plant eased dropsy, a disorder in which fluid accumulates in the legs because the heart tails to pump blood adequately. The doctor explained, "t was told that this use of foxglove had long been kept a secret by an old woman in Shropshire, who had sometimes made cures after the more regular practitioners had failed.

 " The active ingredient in foxglove is digitalis. Today. drug companies and re-searchers seek medicinal plants in a:I corners of the world. With more than 450,000 plant species to examine, the search must necessarily be focused on plants with high probability of yield-in• useful drugs. How do%ive identify such plants? By consulting indigenous healers—local people whose ancestors have lived in the area for genera-_"The leaves and flowers of this plant (Cornutia pyramidata) are used to treat skin rashes.

 The knowledge such healers possess is quite remarkable. Samoan healers treat yellow fever (a viral disease) with brews made by steeping the wood of a certain tree in water. Researchers have discovered that the active ingredient in this brew is effective against the virus that causes AIDS. In Thailand, healers use

the roots of a plant related to ginger to ease stomach pains and other gastrointestinal disorders.

 A chemical in this plant is now known to kill parasitic worms, such as tapeworm and hook-worm. In India, healers treat snake-bites and mental illness with the roots of a climbing shrub called Indian snakeroot. The active ingredient in these roots is reserpine, now prescribed throughout the world for high blood pressure. In Peru, the Jivaro Indians use sap from a particular tree to make wounds heal more rapidly. The active ingredient in this sap is now being tested for its healing properties.

 Materials isolated from plants now account for about 25% of all prescriptions issued in North America. Some of these drugs are listed in table 13.A. How do we thank the local healers, in various isolated regions of the world, for this invaluable knowledge? Many drug companies and research groups are now arranging to provide these peoples with a share of the royalties earned from the drugs. Many of these cultures, however, value their land and its forests more than they value money. Hence, in many places, such as Costa Rica and Samoa, the royalties from drugs are used to preserve local forests.