Plants​—A Valuable Source of Medicines

Experts estimate that a quarter of all the modern-day pharmaceuticals that people rely on started out​—wholly or in part—​as chemicals that occur in plants. This fact is often cited by those who promote various herbal remedies.

Most research being done on medicinal plants is directed toward isolating active compounds. A foremost example of such a compound is aspirin, which is derived from salicin, found in the bark of the white willow tree.

Once isolated, active compounds found in a plant can be administered in a sufficient and more precise dosage. One reference work states: “To take enough willow bark to achieve the benefits aspirin provides or to take enough foxglove to achieve the full lifesaving effects of digitalis is much more easily accomplished via a pill than by eating natural substances.”

On the other hand, isolating the active compound from a medicinal plant can have its drawbacks. For one thing, it may mean losing any nutritional and possible medicinal benefits provided by other substances in the plant. What is more, some of the organisms that cause disease have become resistant to the drugs that target them.

Quinine, a substance derived from the bark of cinchona trees, provides an example of the drawbacks of isolating the active compound from a medicinal plant. While the quinine kills a huge percentage of malaria-causing parasites, those parasites it does not kill become increasingly plentiful as other parasites die. One reference work explains: “Such resistance has become a major issue in medicine.”

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Aspirin is obtained from this white willow tree

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USDA-NRCS PLANTS Database/Herman, D.E. et al. 1996. North Dakota tree handbook

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The cinchona tree, from which quinine is obtained

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Courtesy of Satoru Yoshimoto