herbal medicine use of natural plant substances (botanicals) to treat and prevent illness. The practice has existed since prehistoric times and flourishes today as the primary form of medicine for perhaps as much as 80% of the world's population. Over 80,000 species of plants are in use throughout the world. Along with acupuncture , herbal medicine is considered primary health care in China, where it has been in documented use for over 2,500 years.

Herbs may be used directly as teas or extracts, or they may be used in the production of drugs. Approximately 25% of the prescription drugs sold in the United States are plant based. Many more herbal ingredients are present in over-the-counter drugs, such as laxatives. Medicines that come from plants include aspirin from willow bark ( Salix species) and digitalis from foxglove ( Digitalis purpurea ).

Scientific interest in herbal medicine in the United States has lagged behind that in the countries of Asia and W Europe; in Germany, for example, one third of graduating physicians have studied herbal medicine, and a comprehensive therapeutic guide to herbal medicines has long been published there. Nonetheless, millions of people in the United States use herbal products to treat a wide variety of ailments or to enhance health. Among the more popular remedies used are ginseng , to increase stamina and as a mild sedative; St.-John's-wort , for mild depression; echinacea , to aid the immune system and alleviate colds; kava, to calm anxiety and treat insomnia; saw palmetto, for enlarged prostate; and ginkgo biloba, to improve short-term memory (see ginkgo ). Some people have used botanicals in an attempt to stave off serious illnesses such as AIDS.

This widespread use has prompted demands that herbal remedies be regulated as drugs to insure quality standards. The U.S. Food and Drug Administration (FDA) can require a clinical trial on any herb that has a health claim on its label, but medical testing, which is geared toward observing a particular active component, is difficult to apply to herbs, which may have many interacting ingredients. Debate over botanicals' validity and safety as medicines and over the appropriate degree of government regulation continues. The Dietary Supplement Health and Education Act, passed in 1994, reclassified herbs as dietary supplements rather than food additives. It forbids unreasonable health claims by the manufacturers, but makes it the FDA's responsibility to prove that a marketed product is unsafe. (In contrast, in prescription and over-the-counter drugs, it is the manufacturer's responsibility to prove safety and effectiveness before a drug can be marketed.)

Another concern surrounding herbal medicine is the availability of wild plants for a growing market; it is feared that the limited supplies of known wild herbs are being threatened by overharvesting and habitat loss. The potential of isolating beneficial drugs from plants, however, has prompted large pharmaceutical companies to contribute to the conservation of the tropical rain forest. Biologists have called for more careful study of medicinal plants, especially regarding their capacity for sustainable harvesting and the effects of cultivation on their efficacy as medicaments.

Bibliography: See V. E. Tyler and S. Foster, Tyler's Honest Herbal (rev. ed. 1999); The Physicians' Desk Reference for Herbal Medicines (annual).

herbal medicine Plants have been used for medicinal purposes for as long as history has been recorded. China, India, Egypt, and Assyria appear to have been the places which cradled the use of herbs, but herbalism was common in Europe by medieval times. Despite the progress in orthodox medicine, interest in alternative medicine, including herbalism, is on the increase in the West — and for 80% of the world herbal medicine is still the only kind to which ordinary persons have ready access.

A great variety of plants are used for medicinal treatments. Either the dried plant, or a specific part of it (root, leaves, fruit, flowers, seeds), is formulated into suitable preparations — compressed as tablets or made into pills, used to make infusions (teas), extracts, tinctures, etc., or mixed with excipients to make lotions, ointments, creams, etc. Few herbal drugs are subject to legislative control. Obviously control is needed for poppy capsules (which contain opium), belladonna, digitalis, nux vomica beans (which contain strychnine), and rauwolfia (which contains reserpine). Most herbal remedies are freely available, although rarely have any been investigated with the thoroughness of orthodox medicines. The claims made for many herbal remedies are for trivial or minor ailments, due partly to the strictures put on legal claims for efficacy, and partly because herbalists claim to treat the whole person to restore normal physiological balance, rather than to treat or cure a particular medical illness. Activities of herbal medicines are often described in very general terms — such as carminative, laxative, demulcent, antitussive, expectorant, sedative, antiseptic, or astringent. Unlike orthodox medicines, which usually consist of a single, isolated principle often synthetic), plants or extracts of plants contain multiple constituents, not all of them active. Herbalists often claim that the admixture of multiple constituents leads to synergism between the active moieties. Similarly, many consider that since plants are natural materials they are safer and will produce fewer side-effects than synthetic drugs. There is little substance or reason in either of these claims. For example, comfrey (Symphytum officinale) is considered a safe herb and is used as a demulcent. However, it contains pyrrolizidine alkaloids, which are toxic to the liver and can cause liver cancer. Media attention can often cause a major increase in the demand and use of herbal drugs — for example, evening primrose oil, feverfew, Ginko biloba, and ginseng. One of the problems with herbal drugs, especially those with active principles which have well-defined medicinal effects (e.g. digitalis), is that the amount of active principle(s) varies according to the location where the plant is grown, the prevailing weather conditions, etc., so it is vital in these instances that the crude material is assayed appropriately so that the dosage can be accurately controlled, especially where the therapeutic ratio is low. (Therapeutic ratio is the ratio of the dose causing toxic effects to that required for treatment.)

From time to time new drugs are discovered from herbal sources — for example, taxol, derived from the yew, is an important drug for some forms of cancer. The active principle is extracted and purified from plant material for as long as that process remains economically viable compared with chemical synthesis.

Alan W. Cuthbert

Herbal Medicine

Using medicines derived from plants is a practice probably as old as humankind itself. Prehistoric peoples likely noted when consuming a particular plant part provided relief, such as willow bark "tea" lowering a fever. Sumatran clay tablets engraved forty centuries ago list plant-based remedies for common ills, as do ancient writings from Egypt and China. In nineteenth-century United States, St. John's wort and Echinacea were just two of many commonly used herbal remedies.

Many modern medicines are synthetic versions of plant-derived "natural products." A compound from a periwinkle plant, for example, served as the basis for a powerful drug that fights leukemia. Poppies provide alkaloids such as morphine that are potent painkillers.

In the U.S. today, one-third of all adults have tried herbal treatments, creating a multibillion-dollar market. The resurgence of interest in herbal medicine is largely due to the Dietary Supplements Health and Education Act (DSHEA) of 1994, which expanded the definition of "dietary supplement" beyond essential nutrients to include "herbs and botanicals," thus removing them from regulation as drugs. This designation means that labels can only mention ways that the herbal product can promote health, not cure disease. For example, valerian root "promotes restful sleep," St. John's wort "may help enhance mood," and Echinacea and goldenseal "may help support the immune system." Table 1 lists some herbal products marketed as food supplements that are currently being tested for efficacy in treating specific illnesses. Many physicians and biochemists argue that active ingredients in many herbal remedies are indeed drugs, and should be regulated as such.

The U.S. Food and Drug Administration does not require food supplements to be tested for safety and efficacy in treating illness, or even that a product be consistent in concentration of the active ingredient, or the plant part from which it is derived. Two-thirds of individuals who take herbal supplements do so without consulting a physician, which can be dangerous. St. John's wort, for example, interacts with enzymes that control blood levels of many drugs, including anesthetics and drugs that transplant recipients must take. Some herbal supplements may be dangerous if taken in large

doses or by individuals with particular illnesses. For example, Ginkgo biloba has been linked to intracranial bleeds, and Ephedra to seizures, hypertension, stroke, and death.

Studies to test effects of herbal substances may be flawed or yield inconsistent results. Some reports are actually studies of studies, selected in a way that prejudices the results. Many trials are too small or not well enough controlled to yield meaningful conclusions. Consider an investigation on whether fruits of the chastetree can prevent symptoms of premenstrual syndrome. For three months, 1,634 women took two capsules a day of the extract, and reported their symptoms before and after the trial period—with no control group not receiving the drug. For St. John's wort, one large investigation found it to be just as effective as a standard antidepressant drug, yet another large study published a few months later found it to be useless.

Not all herbal remedies lack scientific backing due to the peculiarities of regulatory law or variations in experimental design. For example, people have drunk cranberry juice to ease symptoms of urinary tract infections for many years. The effect was thought to be due to increasing acidity of urine, but a 1998 study found that compounds called proanthocyanidins prevent bacterial outgrowths from adhering to the wall of the uterine tract.

It is wise to consult a physician when considering use of an herbal product. Even for a well-understood remedy such as cranberry extract, additional therapy may be required, or drug interactions a possibility. The law may not currently consider herbal ingredients to be drugs, but science indicates otherwise.

see also Clinical Trials; Ethnobotany; Psychoactive Drugs; Secondary Metabolites in Plants

Ricki Lewis

Bibliography

Attenborough, David. The Private Life of Plants. Princeton, NJ: Princeton University Press, 1995.

Fleming, G. Alexander. "The FDA, Regulation, and the Risk of Stroke." The New England Journal of Medicine 343, no. 25 (21 December 2000): 1886–1887.

Shelton, Richard C., et al. "Effectiveness of St. John's Wort in Major Depression." The Journal of the American Medical Association 285, no. 15 (18 April 2001): 1978–1986.

Simpson, Beryl Brintnall, and Molly Conner Ogorzaly. Economic Botany: Plants in Our World, 3rd ed. New York: McGraw-Hill Higher Education, 2000.