Aging Begins at 30

Plant Sources of Useful Drugs

What do aspirin, codeine, ipecac, reserpine, scopolamine, theophylline, and vinblastine have in common? They are all flowering plants or fern-derived drugs (as compared with those from microorganisms of fungi). Twenty-five percent of all drugs prescribed every year in America are from plant sources. One hundred and twenty different drugs fall into this category. Perhaps these chemicals were evolved as plant defenses against predators or infection.

Digitalis from the foxglove plants used by an old woman in Shropshire, England was analyzed and promoted for heart disease by Dr. William Withering in 1785 and was still widely used in herbal form until the 1950's. But like many medicines, its active drug has since evolved, not only into more measurably purer forms, but into forms with predictable duration and less unwanted properties.

Some other types of drugs have been developed through recognition of unwanted effects of the original drug. For example, sulfonamides used for infection were noted to lower blood sugar and led to drugs such as tolbutamide (Orinase®) for diabetes. Minoxidil, now used for hair growth, was originally developed for high blood pressure. Now that body cell receptors for some drugs are known, computers can be used to design drugs that fit. In other cases, a drug that works by mouth can be changed for use by inhalation. inhaled corticosteroids used for asthma are a good example where unwanted side effects of a drug taken by mouth are avoided. The new nonsedating antihistamine are another example of modification of drugs so as to reach the desired targets in the body and not the brain.

The marketing of a drug in this country takes 10 years and costs about 200 million dollars. Understandably no company would want to pay these costs for drugs with limited use for uncommon conditions like hemophilia, leprosy or Paget's disease. These drugs are called orphan drugs and are allowed to have less premarketing testing. Some drugs for the desperately ill, as for AIDS, are made available while testing is still in progress.

But back to botany, there are 265,000 flowering plants on earth and less than 1% have been extensively studied chemically. A recently studied drug is Taxol® for ovarian and metastatic breast cancer. It comes from the Pacific yew tree. (Yew is the old English name for the hunting bow made from that tree.) Fortunately for the yew tree, Taxol® has recently been synthesized. Ethnobotanists have a strategy in collecting plants that might yield useful drugs. Indigenous use of plants by generations of native healers, particularly in plant-rich rain forests, indicates plants worthy of study. "Informed consent" is obtained from the tribes and a significant part of any royalties are returned to the natives to preserve the rain forests and to prevent accumulated medical wisdom dying out with the native healers. This has been done in Samoa and Belize.

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