Botanical Name: Rhamnus purshiana, Rhamnaceae

Botanical synonyms:R. purshianus,Frangula purshiana

Common names: Cascara, Cascara Sagrada, Chittem bark

Similar species:Rhamnus lanceolata, R. alnifolia, R. californica, R. crocea, R. cathartica, R. frangula

Plant description: Cascara is an erect, tall shrub or small tree up to 10 m tall, with a thin, smooth silvery-gray bark, that has a numbing, bitter taste.  The leaves are alternate or opposite (in new growth), typically deciduous, 6-12 cm long, egg-shaped to oblong, and deep, glossy green.  When young they are covered with a dense pubescence on the under surface, but become glabrous when old.  The leaf margin is regularly dentate, with numerous small, serrate teeth, except at the base.  The leaf surface is pinnately veined in furrows, giving it an almost washboard appearance. The flowers are small, greenish-yellow, with five sepals, petals and stamens, between 8-50 appearing in umbrella-like clusters, typically after the leaves have matured. The fruit is a small purplish-black drupe, obtusely 3-angled, about 5-8 mm across, containing three black, shining seeds (Pojar and MacKinnon 1994, 90; Felter and Lloyd 1893).

Habitat, ecology and distribution: Cascara is found in shady spots, in dry to wet locations, in mixed deciduous-conifer forests.  It is especially common in heavily timbered forests (Moore 1993, 304), favoring southern aspects, and on the coast of B.C., in swampy areas with alder and vine maple (Pojar and MacKinnon 1994, 90).  Although under increasing strain from human development, most Cascara can be found in the temperate rainforests of southern coastal British Columbia and Washington.  Less frequently Cascara occurs in the southern Columbia mountains of B.C. around the Arrow Lakes and Fraser River basin, and southward into Idaho and Montana.  Cascara's natural range extends down into Oregon, but excessive and improper harvesting during the turn of the 20th century severely impacted native populations.  In the Rocky Mountains the much smaller shrub Alder-leaved Buckthorn (R. alnifolia) can be found, and in California Cascara gives way to Coffeeberry (R. californica) and Mountain Holly (R. crocea).  European species of this genus include R. frangula and R. cathartica, which were introduced and have since naturalized on the eastern coast of the continental United States.

Part used: Most herbalists recommend the bark, aged at least one year or heated in a food dehydrator at 80-90 degrees Celsius for at least 24 hours, and then powdered. (Moore 1993, 304).  In his report entitled The Cascara Tree in British Columbia (1942), botanist John Davidson states however that the finely powdered wood is a more efficient remedy than the coarsely powdered bark alone.  This would require turning harvested branches or trees into sawdust, and preparing an extract from this.  In any case the bark should be harvested conservatively if the intent is not to kill the tree, never taking bark from the main trunk, and only in the summer when the weather is dry.

History: Felter and Lloyd state that Cascara was "discovered" by an Eclectic physician named Dr. J. H. Bundy, and its virtues first mentioned in New Preparations, published in Detroit in 1877.  Its common name 'Cascara Sagrada' however means 'Holy Bark,' the name given to it by Spanish explorers who were gratified when it was introduced to them by the First Nations people, as a corrective to the bowels after long months of inactivity and preserved food. All First Nations groups along the Pacific Northwest, including the Nuxalk, Coast Salish, Quileute, Nu-chah-nulth and Kwakwaka'wakw, used Cascara as a laxative.  Traditionally the Coast Salish aged the bark to prevent nausea and griping, and prepared a decoction that was also used to wash sores, muscle strains and swellings. The pharmaceutical company Parke, Davis & Co. first introduced the fluid extract to the medical profession during the late 19th century, and is thus largely responsible for its widespread acceptance in the marketplace (Felter and Lloyd 1893). A bitter-tasting Cascara extract has also been used in liquors and a debittered extract as a flavouring for drinks and ice cream.

Constituents: Cascara contains about 6-9% anthraquinone (hydroxyanthracene) glycosides, the major proportion (60-70%) that distinguishes Cascara from other anthraquinone-containing herbs being cascarosides A and B (aloin O- and C- glycosides), and cascarosides C and D (deoxyaloin O- and C- glycosides).  Other anthraquinones include barbaloin (from aloe-emodin) and chrysaloin (from chrysophanol anthrone), as well as aloe-emodin, chrysophanol and emodin in a free state.  Various dianthrones (of aloe-emodin, chrysophanol and emodin) have been detected, as well as the heterodianthrones palmidin A, B and C.  Other constituents include linoleic acid, myristic acid, sytinigic acid, lipids, resin and tannins (Newall et al 1996, 62; Evans 1989, 407).

Medical Research:
•Gastrointestinal: Medicinal plants that contain anthraquinone glycosides have been well known to researchers since the late 19th century, when they began to be used by medical doctors instead of other purgatives such as  mercury (calomel).  Hydroxyanthracene glycosides are stated to be poorly absorbed by the gastrointestinal epithelium, but are hydrolyzed by bacteria into active aglycones that are absorbed by the colon.  In tests using radiolabeled C-rhein anthraquinone, upwards of 37-60% of the oral dose can be absorbed in rats (Boik 1995, 118).  These compounds are then excreted in the feces and urine, imparting a distinctive orange colour.  If taken long term these compounds can even stain the colon and interrupt the normal function of the colonic mucosa (see Contraindications and cautions, below). The hydroxyanthracene aglycones act to promote bowel movements by inhibiting the absorption of water and electrolytes from the colon, as well as by promoting active secretion into the lumen of the bowel.  The resulting pressure from the increased volume of the colon contents results in the stimulation of stretch receptors that promote peristalsis (Bradley 1992, 99).
•Antitumor: Apart from its effects upon digestion, anthraquinones such as rhein and emodin have undergone a significant degree of investigation for their antitumor properties.  Both rhein and emodin have demonstrated cytotoxic properties, and in neoplastic animal and human cell lines have been shown to inhibit protein synthesis, destroy the integrity of the plasma membrane and enhance lipid peroxidation (Boik 1995, 117-18).  In addition, both compounds have demonstrated antitumor properties in vivo, increasing survival times and inhibiting tumor progression in animal models (Boik 1995, 117-18).

Toxicity: None. 

Herbal action: aperient, laxative, cholagogue, antirheumatic, antitumor

Indications: Constipation from dietary indiscretions or atonic states of the intestines, constipation with hemorrhoids, constipation with intestinal spasm, rheumatism, cancer.

Contraindications and cautions: It has been suggested that the anthranoids exert their laxative effect by damaging the epithelial cells of the colon, leading to changes in absorption, secretion and motility. These damaged epithelial cells can be found as apoptotic bodies in the pigmented colonic mucosa, and have been associated with an increased risk of colorectal cancer (van Gorkom et al 1999).  Whether or not the long term use of herbs like Cascara are an actual risk factor in cancer however is still unknown, especially considering conflicting evidence that demonstrates antitumor properties for anthraquinones.  Nonetheless, the long term use of Cascara is not recommended.  It is inappropriate for use in pregnancy, and as anthrones and anthranols can be passed into the breast milk, it is best avoided during lactation.

Medicinal uses: There is no doubt that Cascara has long been relied upon as a treatment for chronic and occasional constipation, and despite gaining widespread acceptance by mainstream North American society relatively recently, it has since become one of the most important herbs used by herbalists to treat constipation. Unlike other laxatives such as Senna (Cassia angustifolia), Cascara is said to restore tone to the entire intestinal tract, probably through the activity of its bitter principles and tannins.  Although aging or heating the bark appears to decrease its spasmogenic properties, most herbalists will tend to combine Cascara with antispasmodic herbs such as Zingiber to prevent any adverse effects.  It is also known that with similar herbs, such as the Chinese Rheum palmatum, that boiling the bark or wood for at least an hour and a half can reduce the purgative property upwards of 50% (Boik 1995, 119).  This latter technique is especially important if the intent is to take advantage of Cascara's antitumor properties, without the need to necessarily stimulate bowel movements. For general use Cascara is recommended by King's in doses of 10 drops, after meals, for treating headaches and dyspepsia that are secondary to constipation, as well as to stimulate bowel evacuation and promote the tone of the rectum in the treatment of hemorrhoids (Felter and Lloyd 1893).  In larger doses it acts more strongly, and in chronic cases larger doses are likely to be more effective than smaller doses, at least at the outset of treatment.  As a general rule however, Felter and Lloyd recommend small doses that are "…gradually increased, until the desired action is obtained, and then to gradually withdraw the drug" (1893).  Generally speaking, Cascara is a very graceful remedy for constipation, usually acting without griping or irritation, producing a semi-fluid stool. Cascara is also a possible treatment for chronic diarrhea, when the cause is an atonic state, or in hepatic congestion, with jaundice. Felter and Lloyd also mention the efficacy of Cascara in the treatment of rheumatism, in doses of 10-15 drops (1893).

Pharmacy and dosage:
•Dry Plant Tincture: aged bark or whole wood, 1:5, 50% alcohol, 3-20 gtt
•Decoction: 1:20, 30-120 mL
•Powder: 250-1000 mg

REFERENCES

Boik, John. 1995. Cancer and Natural Medicine. Princeton, MN: Oregon Medical Press
Bradley, Peter R. ed. 1992. British Herbal Compendium. Bournemouth, UK: British Herbal Medicine Association.
Davidson, John. 1942. The Cascara Tree in British Columbia. Victoria: Province of British Columbia, Minister of Agriculture.
Evans, W.C. 1989. Trease and Evans Pharmacognosy London: BailliËre Tindall.
Felter, HW and JU Lloyd. 1893. King's American Dispensatory. Digitized version available from http://www.ibiblio.org/herbmed/eclectic/kings/main.html.
Moore, Michael. 1993. Medicinal Plants of the Pacific West. Santa Fe: Red Crane.
Newall, Carol A., Linda A. Anderson and J.D. Phillipson. 1996. Herbal Medicines: A Guide for Health-Care Professionals. London: The Pharmaceutical Press.
Pojar, Jim and Andy MacKinnon, comp. and eds. 1994. Plants of Coastal British Columbia. Vancouver: Lone Pine
van Gorkom BA, de Vries EG, Karrenbeld A, Kleibeuker JH. 1999. Review article: anthranoid laxatives and their potential carcinogenic effects. Aliment Pharmacol Ther Apr 13(4):443-52