Frangula purshiana (cascara, cascara buckthorn, cascara sagrada, bearberry, and in the Chinook Jargon, chittem stick and chitticum stick; syn.Rhamnus purshiana) is a species of plant in the family Rhamnaceae. It is native to western North America from southern British Columbia south to central California, and eastward to northwestern Montana.
Cascara is a large shrub or small tree 4.5–12 metres (15–39 feet) tall,[2] with a trunk 20–50 centimetres (8–20 in) in diameter.[3] The buds have no scales, unique for the northwest region.[2]
The thin bark is brownish to silver-gray with light splotching[2] (often, in part, from lichens); the inner bark is smooth and yellowish (turning dark brown with age and/or exposure to sunlight).[4][5] Cascara bark has an intensely bitter flavor that will remain in the mouth for hours, overpowering and even numbing the taste buds.[6][2]
The leaves are simple, deciduous, alternate, clustered near the ends of twigs. They are oval, 5–15 cm (2–6 in) long and 2–5 cm (3⁄4–2 in) broad with a 0.6–2 cm (1⁄4–3⁄4 in) petiole, shiny and green on top, and a dull, paler green below;[7] they have tiny teeth on the margins, and 10–12 pairs of pinnate veins.[2][8] The leaves turn yellow in autumn.[2]
The flowers are tiny, 3–5 mm (1⁄8–1⁄4 in) 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.[9] The fruit is a drupe 6–10 mm (1⁄4–3⁄8 in) 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.[10][11]
Closeup of leaf and buds
Splotchy bark
Branch with prominently veined, alternate leaves, reddish twigs, and clusters of flowers at the leaf axils
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.[9]
Ecology
The fruit is eaten by birds, bears, raccoons,[15] and other mammals,[16] who distribute the undigestible seeds.[2]
Cascara is shade tolerant.[2] Its trees create brushy stands which provide abundant thermal cover and hiding places for wildlife.[17]
Cascara is usually top-killed by fire, but may resprout from the root crown. After more severe fires, it reestablishes via off-site seed beginning the second year after the fire. It typically inhabits areas with fire regimes on 30 to 150 year intervals, although it is also found in areas with fire regimes of 500+ years.[17]
Toxicity
The fruit and bark contain a bitter chemical making them inedible to humans, although there are contested medicinal uses.[2]
Cascara is sold in the United States as a natural "dietary supplement" rather than a drug, and its common use is ingested by mouth to relieve constipation.[18] Although it may be safe for use over a few days, there is insufficient scientific evidence to assure its safety and effectiveness.[18][20] Use of cascara may adversely affect the actions of various prescribed drugs, such as digoxin, warfarin, corticosteroids, and diuretic agents.[18]
Phytochemistry
Numerous quinoid phytochemicals are present in cascara bark.[20] The chemicals possibly contributing to a laxative effect are the hydroxyanthraceneglycosides, which include cascarosides A, B, C, and D.[20] Cascara contains approximately 8% anthranoids by mass, of which about two-thirds are cascarosides.[25] The hydroxyanthracene glycosides may trigger peristalsis by inhibiting the absorption of water and electrolytes in the large intestine, which increases the volume of the bowel contents, leading to increased pressure.[18][20]
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.[citation needed] Some of the chemical constituents present in the bark may be excreted by the kidneys.[26] The extract from cascara bark also contains emodin, which may contribute to the laxative effect.[27]
Uses
Traditional medicine
Cascara was used in traditional medicine as a laxative.[18][20] The dried, aged bark of R. purshiana used by indigenous native cultures and immigrant Euro-Americans as a laxative is similar to other anthraquinone-containing herbal preparations of leaves and fruits of senna, the latex of Aloe vera, and the root of the rhubarb plant.[28] Commercially, it is called "cascara sagrada" ('sacred bark' in Spanish), while in the traditional Chinook Jargon it is known as "chittem bark" or "chitticum bark".[20] Following its introduction to formal U.S. medicine in 1877, it replaced the berries of R. catharticus as the favored laxative.[2] The historical interest in using cascara damaged native cascara populations during the 1900s due to overharvesting.[29]
Preparation in folk medicine
The bark is collected in the spring or early summer, when it easily peels from the tree.[30]
Once stripped from the tree, the bark must be aged for several months, 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.[20] Botanist J. Morton suggests using a dose of 10–30 grains, dissolved in water, or 0.6–2.0 cc for fluid extract.[citation needed][31]J.A. Duke suggests an effective dosage is approximately 1–3 grams (15–46 gr) dried bark, or 1–2.5 grams (15–39 gr) powdered bark.[23]
Other uses
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.[32][31][22](p 130) 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.[22](p 131) Due to its bitter taste, cascara can be used to stop nail-biting by applying it to the fingernails.[22](p 131)
^Barceloux, Donald G. (2008). "Cascara". Medical Toxicology of Natural Substances: Foods, fungi, medicinal herbs, plants, and venomous animals. John Wiley & Sons. p. 1034. ISBN9781118382769 – via Google Books.
^Little, Elbert L. (1994) [1980]. The Audubon Society Field Guide to North American Trees: Western Region. Knopf / Chanticleer Press. p. 550. ISBN0394507614.
^ abcd
Small, Ernest; Caitling, Paul M.; et al. (National Research Council Canada) (1999). Canadian Medicinal Crops. NRC Research Press. pp. 129–131. ISBN9780660175348 – via Google Books.
^Cassileth, Barrie R.; Yeung, K. Simon; Gubili, Jyothirmai (2010). Herb-Drug Interactions in Oncology. Memorial Sloan-Kettering Cancer Center, Integrative Medicine Service (2nd ed.). Shelton, CT: Peoples' Medical Publishing House (PMPH-USA). p. 146. ISBN978-1-60795-041-7.