Rhamnus purshiana (cascara buckthorn, cascara, bearberry, and in the Chinook Jargon, chittem and chitticum; syn. Frangula purshiana, Rhamnus purshianus) is a species of buckthorn native to western North America from southern British Columbia south to central California, and eastward to northwestern Montana.
The dried bark of cascara has been used for centuries as a laxative, first by Native Americans in the Pacific Northwest, and then by European/U.S. colonizers. The chemicals primarily responsible for the laxative action are the hydroxyanthracene glycosides (particularly cascarosides A, B, C and D), and emodin. These act as stimulant laxatives, with the hydroanthracene glycosides stimulating peristalsis, and emodin exciting smooth muscle cells in the large intestine.
The outer bark is brownish to silver-grey with light splotching (often, in part, from lichens) and the inner surface of the bark is smooth and yellowish (turning dark brown with age and/or exposure to sunlight). Cascara bark has an intensely bitter flavor that will remain in the mouth for hours, overpowering the taste buds.
The leaves are simple, deciduous, alternate, clustered near the ends of twigs. They are oval, 5–15 cm long and 2–5 cm broad with a 0.6–2 cm petiole, shiny and green on top, and a dull, paler green below; and have tiny teeth on the margins, and parallel veins.
The flowers are tiny, 4–5 mm diameter, with five greenish yellow petals, forming a cup shape. The flowers bloom in umbel-shaped clusters, on the ends of distinctive peduncles that are attached to the leaf axils. The flowering season is brief, from early to mid- spring, disappearing by early summer. The fruit is a drupe 6–10 mm diameter, bright red at first, quickly maturing deep purple or black, and containing a yellow pulp, and two or three hard, smooth, olive-green or black seeds.
Range and habitat
Cascara is native from northern California to British Columbia and east to the Rocky Mountains in Montana. It is often found along streamsides in the mixed deciduous-coniferous forests of valleys, and in moist montane forests. Cascara is common in the understory of bigleaf maple forest, alongside red osier dogwood and red alder.
In many areas, the high market demand for cascara bark has led to over-harvesting from wild trees, which may have heavily reduced cascara populations.
The dried, aged bark of R. purshiana has been used continually for many years by both Pacific northwest native peoples and immigrant Euro-Americans as a laxative natural medicine, as one of several anthraquinone-containing herbal medicines including the leaf and fruits of senna, the latex of Aloe vera, and the root of the rhubarb plant. Commercially it is called "Cascara Sagrada" ('sacred bark' in Spanish), while traditionally it is known as "chittem bark" or "chitticum bark".
Spanish conquerors exploring the Pacific Northwest in the 1600s came across many Native peoples using the bark of R. purshiana as a laxative. They gave it the name "Sacred Bark" (cáscara sagrada) in honor of its effectiveness. By 1877 the U.S. pharmaceutical company Parke-Davis was producing cascara preparations, and soon afterwards cascara products were being exported overseas to European markets. The explosion of the cascara industry caused great damage to native cascara populations during the 1900s, as a result of overharvesting.
In 1999, cascara made up more than 20% of the national laxative market in the U.S., with an estimated value of $400 million. The bark itself was worth approximately $100 million. Cascara was found in more drug preparations than any other natural product in North America, and is believed to be the most widely used cathartic in the world.
Numerous quinoid substances are found in the bark of cascara. The chemicals primarily responsible for the laxative action are the hydroxyanthracene glycosides, which includes cascarosides A, B, C, and D. Cascara contains approximately 8% anthranoids by mass, of which about two-thirds are cascarosides. The hydroxyanthracene glycosides act as a stimulant laxative by exciting peristalsis in the colon. They trigger peristalsis by inhibiting the absorption of water and electrolytes in the large intestine, which increases the volume of the bowel's contents, leading to increased pressure.
The hydroxyanthracene glycosides are not readily absorbed in the small intestine but are hydrolyzed by intestinal flora to a form that is partly absorbed in the colon. Hydrolysis of the cascarosides results in the formation of aloins such as barbaloin and chrysaloin. Some of the chemical constituents present in the bark may be excreted by the kidney following medicinal use, resulting in a harmless change in the color of the urine.
Studies have shown that the extract from cascara bark also contains a substance called emodin, which may have anti-cancer effects. Emodin is also responsible for some of the laxative effect, due to its excitation of smooth muscle cells in the large intestine.
The bark is collected in the spring or early summer, when it easily peels from the tree. Once stripped from the tree, the bark must be aged for at least 1 year before use, because fresh cut, dried bark causes vomiting and violent diarrhea. This drying is generally done in the shade to preserve its characteristic yellow color. This process can be quickened by simply baking the bark at a low temperature for several hours. In her book, Major Medicinal Plants, Dr. Julia Morton suggests using a dosage of 10–30 grains, dissolved in water, or 0.6–2 cc for fluid extract. The ethnobotanist and herbalist Dr. James A. Duke suggests an effective dosage of approximately 1 to 3 grams (0.035 to 0.106 oz) dried bark, or 1–2.5 grams powdered bark.
Laxative should only be used on a short-term basis (no longer than 7 days), and should not be used by pregnant women (because cathartics such as cascara can induce labor), by lactating women (because the active compounds can be transferred to the infant), or by people with intestinal obstructions or injuries. Laxatives should also not be used by people with Crohn's disease, irritable bowel syndrome, colitis, hemorrhoids, appendicitis, or kidney problems.
Although chronic use of anthranoid-containing laxatives has been hypothesized to play a role in colorectal cancer, no causal relationship has been demonstrated. No specific data on carcinogenicity or mutagenicity are available for Cortex Rhamni Purshianae or the cascarosides. Data for aloin derived from aloe indicate no genotoxic risk. Emodin derived from aloe showed both positive and negative results in vitro, but was negative in vivo. Emodin was mutagenic in the Salmonella / microsome assay, but gave inconsistent results in gene mutation assays. It showed positive results in the test for unscheduled DNA synthesis with primary rat hepatocytes, but negative results in the sister chromatid exchange assay.
Cascara Sagrada was used by Native Americans for centuries, and was accepted into medical practice in the United States in 1877, and by 1890 had replaced the berries of the European buckthorn (R. cathartica) as a commonly used laxative. It was the principal ingredient in many commercial, over-the-counter laxatives in North American pharmacies until 9 May 2002, when the U.S. Food and Drug Administration issued a final rule banning the use of aloe and Cascara Sagrada as laxative ingredients in over-the-counter drug products. Use of Cascara Sagrada has been associated with abdominal pain and diarrhea; it is also potentially carcinogenic. Another study in 1999 states it is not carcinogenic. Aloe emodin one of the constituents of Cascara Sagrada, is present in Aloe Vera and may increase the carcinogenicity of some kinds of radiation, but have a marked anti-viral effect in vitro against both herpes simplex virus (HSV) type 1 and 2
In July 2003, the FDA responded to a citizen's petition filed against the May 2002 final ruling banning the use of cascara sagrada in OTC laxatives  by the American Herbal Products Association (AHPA) and International Aloe Science Council (IASC) (June 2002, CP25) and subsequent data submissions that occurred in October 2002 (SUP14) and December 2002 (SUP15)). In this letter the FDA stated that the American Herbal Products Association Botanical Safety Handbook (1997), the one cited to the FDA in CP25, contained only general information similar to information they already had in 1975. Upon further evaluation of all submitted information it found inadequate support for the petition that cascara sagrada should be generally recognized as safe and effective for OTC use as a laxative.
In September 2003 the FDA also responded to a petition (CP27) that was filed in August 2002 in which the FDA stated that "the agency does not find that the benefits of using cascara sagrada laxative ingredients outweigh the risks" and that the data contained in petition CP27 "do not rule out the possibility that cascara sagrada preparations are genotoxic and/or carcinogenic."
The fruit can also be eaten cooked or raw, but has a laxative effect. The food industry sometimes uses cascara as a flavoring agent for liquors, soft drinks, ice cream, and baked goods. Cascara honey is tasty, but slightly laxative. The wood is used by local people for posts, firewood, and turnery. It is also planted as an ornamental, to provide food and habitat for wildlife, or to prevent soil erosion. Due to its bitter taste, cascara can be used to stop nail-biting by applying it to the fingernails.
In the 1965 comedy film Those Magnificent Men in Their Flying Machines a 1910 air race is held from London to Paris in primitive first-generation aeroplanes. The British, Italians, French, Germans, Americans, Japanese all have entrants. In one scene a British villain, Sir Percy (Terry-Thomas), has laced several drinks of champagne with cascara to disarm his competitors the night before the beginning of the race. A German competitor Captain Rumpelstoss (Karl Michael Vogler) snatches one of the drinks from Sir Percy's hand thanking him while Sir Percy murmurs to himself "serves him right, greedy blighter". The next day at the start of the race, Rumpelstoss is seen running to the restroom and is in no condition to fly because of the cascara in his champagne the night before. His superior (Gert Frobe) takes his place as pilot of the German aeroplane.
- Mahady, Gail B. (2005). "Cascara Sagrada (Rhamnus purshiana)". In Coates, Paul M. Encyclopedia of Dietary Supplements. CRC Press. p. 89. ISBN 9780824755041.
- Henkel, Alice (1909). American medicinal barks. Government Printing Office. p. 39.
- Biddle, John Barclay (1895). Materia medica and therapeutics, for physicians and students. P. Blakiston, Son. p. 360.
- Peattie, Donald C. & Landacre, Paul (1991). A Natural History of Western Trees. Houghton Mifflin Harcourt. p. 633. ISBN 9780395581759.
- Stuart, John D. & Sawyer, John O. (2002). Trees and Shrubs of California. University of California Press. p. 474. ISBN 9780520935297.
- Kricher, John C. (1999). Peterson First Guide to Forests. Houghton Mifflin Harcourt. p. 119. ISBN 9780395971970.
- Tilford, Gregory L. (1997). Edible and Medicinal Plants of the West. Mountain Press Publishing. p. 26. ISBN 9780878423590.
- George Bishop Sudworth, United States Forest Service (1908). Forest trees of the Pacific slope, Volume 11. Government Printing Office. p. 404.
- Barceloux, Donald G. (2008). "Cascara". Medical Toxicology of Natural Substances: Foods, Fungi, Medicinal Herbs, Plants, and Venomous Animals. John Wiley & Sons. p. 1034. ISBN 9781118382769.
- Minnis, Paul E. & Elisens, Wayne J. (2001). Biodiversity and Native America. University of Oklahoma Press. p. 88. ISBN 9780806133454.
- Phillips, Wayne (2001). Northern Rocky Mountain Wildflowers. Globe Pequot. p. 260. ISBN 9781585920945.
- Buchanan, Carol (1999). The Wildlife Sanctuary Garden. Ten Speed Press (original from the University of Wisconsin – Madison). p. 23. ISBN 9781580080026.
- Stargrove, M.B. et al., eds. (2008). Herb, Nutrient, and Drug Interactions: Clinical Implications and Therapeutic Strategies. Elsevier Health Sciences. p. 17. ISBN 9780323029643.
- WHO Monographs on Selected Medicinal Plants, Volume 2. World Health Organization. 2002. p. 259. ISBN 9789241545372.
- Johnson, Rebecca & Foster, Steve (2008). National Geographic Desk Reference to Nature's Medicine. National Geographic Books. p. 77. ISBN 9781426202933.
- Small, Ernest; Caitling, Paul M.; National Research Council Canada (1999). Canadian Medicinal Crops. NRC Research Press. p. 130. ISBN 9780660175348.
- WHO Monographs on Selected Medicinal Plants, Volume 2. World Health Organization. 2002. p. 262. ISBN 9789241545372.
- Schulz, Volker (2004). Rational Phytotherapy: A Reference Guide for Physicians and Pharmacists. Springer. p. 277. ISBN 9783540408321.
- Mahady, Gail B. (2005). "Cascara Sagrada (Rhamnus purshiana)". In Coates, Paul M. Encyclopedia of Dietary Supplements. CRC Press. p. 90. ISBN 9780824755041.
- Cassileth, Barrie R. et al. (2010). Herb-Drug Interactions in Oncology. PMPH-USA. p. 146. ISBN 9781607950417.
- Grieve, Maud (1971). A Modern Herbal: The Medicinal, Culinary, Cosmetic and Economic Properties, Cultivation and Folk-lore of Herbs, Grasses, Fungi, Shrubs, & Trees with All Their Modern Scientific Uses 1. Courier Dover Publications. p. 137. ISBN 9780486227986.
- Castleman, Michael (2010). The New Healing Herbs: The Essential Guide to More Than 125 of Nature's Most Potent Herbal Remedies. Rodale Institute. p. 133. ISBN 9781605298894.
- Kowalchik, Claire et al. (1998). Rodale's Illustrated Encyclopedia of Herbs. The Rodale Institute. p. 68. ISBN 9780875969640.
- Duke, James A. (2002). The Green Pharmacy Herbal Handbook. Macmillan. p. 84. ISBN 9780312981518.
- Small, Ernest; Caitling, Paul M.; National Research Council Canada (1999). Canadian Medicinal Crops. NRC Research Press. p. 129. ISBN 9780660175348.
- Duke, James A. (2002). The Green Pharmacy Herbal Handbook. Macmillan. p. 83. ISBN 9780312981518.
- "Monograph: Cascara Sagrada". webprod.hc-sc.gc.ca. Retrieved 2014-09-23.
- http://apps.who.int/medicinedocs/fr/d/Js4927e/25.html#Js4927e.25 WHO Monograph on Rhamnus purshiana
- Elvin-Lewis, M. (2001). Should we be concerned about herbal remedies? Journal of Ethnopharmacology, vol 75, pp 141–164.
- http://www.unifra.br/pos/aafarm/downloads/_intera%C3%A7%C3%A3o%20medicam_%20plantas4.pdf Should we be concerned about herbal remedies Memory Elvin-Lewis
- http://gut.bmj.com/content/46/5/651.full Anthranoid laxative use is not a risk factor for colorectal neoplasia: results of a prospective case control study
- National Toxicology Program (2010). "Photocarcinogenesis study of aloe vera CAS NO. 481-72-1(Aloe-emodin) in SKH-1 mice (simulated solar light and topical application study)". National Toxicology Program technical report series (553): 7–33, 35–97, 99–103 passim. PMID 21031007.
- http://www.google.com/patents/US4670265 Aloe emodin and other anthraquinones and anthraquinone-like compounds from plants virucidal against herpes simplex viruses
- FDA, "CP25 Response"
- FDA, "May 2002 Final Rule"
- AHPA & IASC, "CP25"
- AHPA & IASC, "SUP14"
- AHPA & IASC, "SUP15"
- FDA, "CP27 Response"
- Burdock, George A. (2005). Flavor ingredients. CRC Press. p. 271. ISBN 9780849330346.
- Small, Ernest; Caitling, Paul M.; National Research Council Canada (1999). Canadian Medicinal Crops. NRC Research Press. p. 131. ISBN 9780660175348.