Poisons and Panaceas: Plants Tell History of Healing
Foxglove, or Digitalis purpurea
Credit: Ivo M. Vermeulen

NEW YORK — Modern medicine owes a great debt to botany. Plants exploited by ancient apothecaries have given rise to more complex and effective cures, and alkaloids isolated from natural herbs have found their way into the neat little pills people get from the pharmacy today.

In a nod to the world's 30,000 herbs that belong to a storied history of healing, botanists have gathered 500 medicinal plants for a living exhibition called "Wild Medicine" here at the New York Botanical Garden.

Leafy inspiration

A quarter of all prescription drugs today are based on plants or compounds discovered inside of them, said botanist Michael Balick, curator of the exhibit,  during a press preview of the show . [See Photos of 7 Potent Plants in the Exhibition]

Foxglove (Digitalis purpurea), beloved by gardeners for its drooping bell-shaped blooms, may be one of the most famous examples. The plant can be deadly if eaten, but it was historically used as a remedy for a wide range of ails, many of which it couldn't actually treat (such as epilepsy).

In the 18th century, William Withering, a British physician and friend of Erasmus Darwin, used infusions of foxglove with surprising success to treat dropsy, a disease now known as edema that can cause swelling bad enough to rip open the skin. More recently, scientists have harnessed chemicals from the plant to create digitalis medications such as digoxin, which is often administered to patients with congestive heart failure.

Rosy periwinkle, too, is toxic to eat, but has been used to treat ailments from diabetes to constipation in traditional Indian and Chinese medicines. Sometimes called Madagascar periwinkle, it's adorned with pink flowers and is endangered in the wild. More than four decades ago, scientists isolated vincristine and vinblastine from the plant, and showed that these alkaloids could be used in chemotherapy treatments. The discovery is often credited with dramatically boosting the survival rate of children with leukemia.

What heals can be a hazard

For foxglove, rosy periwinkle and other potent medicinal plants, the line between poison and panacea is often thin. Opium poppy gave rise to morphine, which revolutionized pain treatment. But the plant is also the source of the highly addictive body-wasting drug heroin. The active agent in curare, a chemical known as tubocurarine, was found to be useful as a muscle relaxer during surgeries and electroconvulsive therapy. But hunters in the Amazon also extracted the chemical from the plant's woody vines to make paralyzing blow darts.

Balick, who is the garden's vice president for botanical science, knows all too well about the dangers of curare.

One night years ago, Balick was up late going through some old materials that he had collected in the field when he stuck himself with a curare dart from the Amazon. When he called his local poison control center and explained his story, the operator told him to call plant expert Michael Balick of the New York Botanical Garden. When he said that he was Michael Balick, the operator told him to go to the hospital. He said he was cleared of any possible toxic effects by the next day.

Are herbs safe?

Medicinal herbs are still widely used in their leafy form, with 4.5 billion people worldwide who incorporate plants into their health regimen, Balick said. He lists among his favorite examples ginger to settle stomachs, turmeric to cut inflammation and pot marigold to treat wounds of the skin.

Though there is evidence to support the effectiveness of many herbs, these plants aren't regulated by the Food and Drug Administration, because the agency considers them food. Drug companies can't patent herbs and they aren't as rigorously tested as pharmaceuticals. What's more, two different batches of the same herb could vary widely in their potency because of the environment in which they were grown, making it difficult to exactly reproduce the plant's effects. [5 Foul Things That Are Good For You]

Balick doesn't administer care to people — "My patients are green," he says — and he is emphatic that all medicines, herbs and pills alike, should be taken under the supervision of a physician. That said, the botanist does believe there is some unnecessary fear about herbal medicine. Like all remedies, herbs must be taken in the larger context of a person's overall health. And like prescription drugs, herbs can sometimes have harmful interactions with other substances.

Grapefruit juice might be the best-known example. In addition to the powerful antioxidant vitamin C, the juice contains a chemical that can disable enzymes needed to break down medications in the digestive system. This means that consuming grapefruit can spike the potency of a long list of drugs, such as cholesterol-lowering statins.

Vanishing wisdom

Many of the plants featured in "Wild Medicine" sit in a replica of Italy's Orto Botanico di Padova in Padua, a UNESCO World Heritage site and the oldest intact academic botanical garden, established in 1545. In a garden like this, Renaissance-era medical students would have studied the labels of the neatly laid plots and learned how to identify plants. And when they didn't have access to the herbs themselves, they would have hit the books. A concurrent exhibition of manuscripts at the New York Botanical Garden offers examples of early botanical textbooks, some of them more than 700 years old.

Other cultures don't have such well-documented traditions, and they're at risk of losing their herbal history. Today, Balick partners with people in far-flung locales like Vanuatu and Micronesia to write manuals of traditional healing practices before they die out.

He told one story of a traditional healer he met in Micronesia whose younger family members received training in Western medicine. When the local clinic ran out of supplies during a dysentery epidemic, the healer was dismayed that her professionally trained young relatives didn't know that the plant growing all around the health care facility was an effective traditional treatment for diarrhea.

"Wild Medicine" is on view until Sept. 8.

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