Herbs for Health: Cancer and the Plant World

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Cancer evokes fear—not only of the disease itself, but also of the treatment, which may itself be painful, mutilating, even life-threatening. In the United States, surgery, radiotherapy, and chemotherapy are the main avenues of treatment. When conventional measures fail or when the condition is termed “untreatable”, many cancer patients—as many as an estimated 50 percent—eventually seek out alternative remedies. In both conventional and alternative approaches to cancer, plants have played an important role.

Five plant-derived drugs are in use in the United States in chemotherapy for the treatment of various kinds of cancer. The National Cancer Institute (NCI) has had a vital part in their clinical development. The institute has been searching for new anticancer agents from plants for more than thirty-five years. From 1960 to 1980, its researchers screened about 35,000 species of higher (flowering) plants for activity against cancer. About 3000 of those demonstrated reproducible activity, and a small fraction of these were eventually chosen for clinical trials.(1)

Mayapple Against Cancer

Long recognized as a medicinal plant, mayapple (Podophyllum peltatum) grows in damp woods from Quebec to Florida and west to Texas and Minnesota. In the last century, mayapple was widely used as a cathartic, emetic, and vermifuge. However, ingesting the root may cause vomiting, diarrhea, headache, bloating, stupor, and/or lowered blood pressure.

While researching podo­phyllin resin obtained from mayapple rhizomes, Jonathan Hartwell, formerly head of NCI’s natural products branch, discovered historical references to the use of mayapple against cancer in many cultures. For example, the Penobscot Indians of Maine used it. An 1849 American materia medica (a treatise on the sources, nature, properties, and preparation of drugs) recommended the resin as a treatment for cancerous tumors, polyps, and “unhealthy granulations”. Physicians in Mississippi used it as early as 1897, and in Louisiana it was a folk remedy for venereal warts. These and other records provided clues in the search for plant sources of anticancer drugs.(2)

Hartwell’s exhaustive survey of the historical and folk lit­erature turned up anecdotal evidence of anticancer activity from more than 3000 plant species.(3) As a result of his efforts, mayapple is now used in conventional cancer treatment. Derivatives of podophyllotoxin, a compound found in the resin, are analogues for two semisynthetic drugs, etoposide and teniposide, which are used in the treatment of testicular cancer and small-cell lung cancer.

Taxol Against Cancer

The pinnacle of NCI’s success in its natural-products screening program is paclitaxel (now better known by its trade name, Taxol), a chemotherapy drug derived from the bark of the Pacific yew (Taxus brevifolia) and the needles of other yew species. (The trade name Taxol is owned by Bristol-Myers Squibb Company, makers of the drug.) (4)

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