Buckthorn is the common name for one of several species of shrubs or small trees of the genus Rhamnus that are used for medicinal purposes. The two most common species are R. frangula and R. cathartica.
R. cathartica is also called common or European buckthorn. It was known as a healing herb hundreds of years ago in Anglo-Saxon England, where it was called waythorn, highwaythorn, hartshorn, or ramsthorn. It is also sometimes called purging buckthorn because of its laxative properties. The berries of European buckthorn can be used in healing. The ripe berries of this species are black and the size of a pea.
R. cathartica is a shrubby tree that grows to a height of about 18 ft (6 m). Its twigs are often tipped with small spines, accounting for the "thorn" in its name. Common buckthorn is found throughout Great Britain, continental Europe, and North Africa, where it grows wild in partial sun along the edges of roads and woodlands. It was introduced into North America as an ornamental landscaping plant, but it has naturalized and become a nuisance plant in much of Canada and the northern United States, where its thick growth crowds out native plants.
R. frangula is shorter, wider, and more shrublike than R. cathartica. It grows in damp soil in Great Britain, continental Europe, and parts of Turkey. It also has been imported into North America. Bark from the trunk and branches of R. frangula is gathered and used in preparing a laxative and a hepatic, or liver medication. R. frangula is also called alder buckthorn, black dogwood, frangula bark, alder dogwood, arrow wood, or Persian berries. It is not related to North American dogwood species.
A third species of healing Rhamnus, R. purshianus, grows in western North America and is called California buckthorn. Its bark also produces a laxative that is milder than those derived from either of the other two species. Sea buckthorn, Hippophae rhamnoides, although it is used in healing and shares a common name with these other species, is not related to the Rhamnus buckthorns, nor is it used in the same ways.
General use
All three types of buckthorn are strong laxatives. The berries of R. cathartica produce the harshest laxative effect (cathartica is a Latin word related to "catharsis", which means purging). The fruit can be used either dried or fresh to treat constipation and to soften stools to give relief from hemorrhoids, anal fissures, or rectal surgery. The berries are also sometimes mixed with other herbs in "blood purifying" formulas.
The dried bark of R. frangula and R. purshianus is also used as laxatives. In earlier times it was used to cleanse the gastrointestinal tract before exploratory surgery. Occasionally buckthorn is used in veterinary medicine as a laxative for dogs.
The laxative effect of all these species is well documented. Buckthorn works by stimulating the large intestine to contract. The contractions shorten the time that waste material remains in the large intestine and allow the formation of softer, moist stools.
In addition to medical uses, buckthorn contains several different pigments used as dyes: yellow from the leaves and bark, green from unripe berries, and blue-gray from ripe berries. R. frangula is also a source of high-quality charcoal used for artistic sketching.
Preparations
The berries of R. cathartica are harvested when ripe. If used fresh, they can be pressed to yield a bitter, extremely foul-tasting juice that can be mixed with sugar and flavorings to produce a laxative syrup. The dried berries are powdered, then added to liquid.
The bark of R. frangula and R. purshianus is harvested in the summer and dried. Young bark is preferred, because the longer the bark is stored, the less potent its laxative properties. Bark used medicinally should be stored at least one year before use. Fresh bark acts as an irritant to the gastrointestinal system. A fluid extract or a decoction is then prepared from the bark and mixed with water and flavorings. The ideal dose is the smallest amount necessary to produce soft stools.
Buckthorn can cause nausea, vomiting, and gastrointestinal spasms in large doses or in sensitive individuals. Buckthorn causes stool to move more rapidly through the large intestine and allows the body less time to reabsorb fluids and electrolytes. Because of this rapid movement, electrolytes can be lost if stools are too frequent and watery. The long-term use of buckthorn can cause potassium imbalances. In rare cases this imbalance can cause heart irregularities, edema, and other serious health reactions.
Interactions
Potassium imbalance is worsened by taking thiazide diuretics, corticosteroids, and licorice root.
BOOKS
PDR for Herbal Medicines. Montvale, NJ: Medical Economics Company, 1998.
OTHER
"Plants for the Future: Rhamnus cathartica and Rhamnus frangula." [cited January 17, 2001]. <http://www.metalab.unc.edu>
