The Alder Buckthorn is a shrub native to Europe and western parts of Asia and is the souce of dried buckthorn bark.
Buckthorn Bark has medicinal uses as a purgative laxative dating back centuries. Buckthorn bark is an ingredient in laxative teas, extracts, and tablets. It is also added to sunscreens. Buckthorn Bark is not approved for use in products in all countries.
The fresh bark contains free anthrone and must be stored for one year or artificially aged by heat and aeration. The use of illegally processed buckthorn bark, fresh bark, will cause severe vomiting, possibly with spasms.
After harvesting, Buckthorn Bark must undergo a further chemical process for at least a year before it is safe to use. The fresh bark is a gastro-intestinal irritant and acts as a poison that causes violent vomiting and abdominal pains. A fermentation process occurs during storage which destroys the emetic frangularoside.
In the United States, Rhamnus purshiana, more commonly known as cascara sagrada, grows throughout northern California and British Columbia. Further down the Pacific coast, R. californica grows. R. frangula is the European species; its fragile wood tastes extremely bitter and it has a strong odor. Although European buckthorn has been cultivated in the United States, most commercial European buckthorn is grown in Eastern Europe and Russia and sold in Europe.
Because the anthraquinones in freshly dried buckthorn bark can cause extreme gastrointestinal irritation, including severe intestinal spasm, as well as vomiting, the bark is aged for a year to allow oxidation of the anthrones, or it is heated and dried in order to induce artificial aging. Either process makes the effects of buckthorn preparations suitable for treating constipation that occurs in patients with hemorrhoids, anal fissures, or post-surgical pain.
The main constituents of the dried bark are the anthraquinone glycosides A and B and frangulins A and B, which make up 3–7%, other anthraquinones, glycosides, dianthrones, aglycones, flavonoids, and tannins.
1,8-dihydroxy-anthracene derivatives have a laxative effect. These compounds increase the motility of the colon by inhibiting stationary and stimulating propulsive contractions. This results in accelerated intestinal passage and, because of the shortened contraction time, a reduction in liquid absorption through the lumen. In addition, stimulation of active chloride secretion increases the water and electrolyte content of intestinal contents.
Drug preparations (herbal stimulant laxatives) have a higher general toxicity than the pure glycosides, presumably due to the content of aglycones.
Experiments pertaining to the genotoxicity of buckthorn and its preparations are not available.
Buckthorn bark is approved for use in some countries for constipation. Other conditions for use include conditions in which soft feces are desirable (hemorrhoids and post rectal-anal operations).
It is not recommended to use any kind of Buckthorn Bark preparations during pregnancy and lactation. Liquid or solid forms of medication are exclusively for oral use. The individually correct dosage is the smallest dosage necessary to maintain a soft stool. In some cases, cramp-like discomforts of the gastrointestinal tract can occur. These incidents require a dosage reduction.