| Frangula purshiana | |
|---|---|
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Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Rosales |
| Family: | Rhamnaceae |
| Genus: | Frangula |
| Species: | F. purshiana |
| Binomial name | |
| Frangula purshiana | |
 | |
| Natural range | |
| Synonyms[1] | |
| |
Frangula purshiana (cascara,cascara buckthorn,cascara sagrada,bearberry, and in theChinook Jargon,chittem stick andchitticum stick;syn.Rhamnus purshiana) is a species of plant in the familyRhamnaceae. It is native to westernNorth America from southernBritish Columbia south to centralCalifornia, and eastward to northwesternMontana.
The dried bark of cascara was used as alaxative infolk medicine by theindigenous peoples of thePacific Northwest, and later worldwide in conventional medicines until 2002.
Cascara is a largeshrub or small tree 4.5–12 m (15–39 ft) tall,[2] with a trunk 20–50 cm (7.9–19.7 in) in diameter.[3] The buds have no scales, unique for the northwest region.[2]
The thinbark is brownish to silver-gray with light splotching[2] (often, in part, fromlichens); 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]
Theleaves are simple,deciduous, alternate, clustered near the ends of twigs. They are oval, 5–15 cm (2.0–5.9 in) long and 2–5 cm (0.79–1.97 in) wide with a 0.6–2 cm (0.24–0.79 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 (0.12–0.20 in) diameter, with five greenish yellow petals, forming a cup shape. The flowers bloom in umbel-shaped clusters, on the ends of distinctivepeduncles 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 adrupe 6–10 mm (0.24–0.39 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 blackseeds.[10][11]
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Cascara is native from northernCalifornia toBritish Columbia and east to theRocky Mountains inMontana.[12] It is often found along streamsides in the mixeddeciduous-coniferous forests of valleys, and in moist montane forests.[13] Cascara is common in the understory ofbigleaf maple forest, alongsidered osier dogwood andred alder.[14]
In many areas, the high market demand for cascara bark led to over-harvesting from wild trees, which may have heavily reduced cascara populations.[9]
The fruit is eaten by birds, bears, raccoons,[15] and other mammals,[16] who distribute the undigestible seeds.[2]
The leaves are browsed bymule deer in Oregon andelk in northern Idaho, especially in the winter months.Olympic black bears,Oregon gray foxes, andraccoons also eat Cascara foliage,[17] as well asring-tailed cats where their range overlaps with Cascara in Northern California.
Cascara isshade 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 withfire regimes on 30 to 150 year intervals, although it is also found in areas with fire regimes of 500+ years.[17]
The fruit and bark contain a bitter chemical making them inedible to humans, although there are contested medicinal uses.[2]
Until 2002, cascara was the principal ingredient in commercial,over-the-counter (OTC)laxatives inNorth Americanpharmacies until theU.S. Food and Drug Administration (FDA) issued a final rule banning the use ofaloe and cascara as laxative ingredients.[18][19] Seriousadverse effects may occur from using cascara, including dehydration, loss ofelectrolyte levels (such as potassium, sodium, chloride), heart rhythm irregularities, and muscle weakness.[18][20] There is also concern for its potentialcarcinogenicity.[21][22] Laxatives should also not be used by people withCrohn's disease,irritable bowel syndrome,colitis,hemorrhoids,appendicitis, orkidney problems.[23][24] Use of cascara is a safety concern for pregnant or breastfeeding women, and for children.[18][20]
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 relieveconstipation.[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 variousprescribed drugs, such asdigoxin,warfarin,corticosteroids, anddiuretic agents.[18]
Numerous quinoidphytochemicals are present in cascara bark.[20] The chemicals possibly contributing to a laxative effect are thehydroxyanthraceneglycosides, 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 triggerperistalsis by inhibiting the absorption of water andelectrolytes in thelarge intestine, which increases the volume of thebowel contents, leading to increased pressure.[18][20]
The hydroxyanthracene glycosides are not readily absorbed in thesmall intestine, but arehydrolyzed byintestinal 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] Theextract from cascara bark also containsemodin, which may contribute to the laxative effect.[27]
Cascara was used intraditional medicine as a laxative.[18][20] The dried, aged bark ofR. purshiana used byindigenous native cultures and settler Euro-Americans as a laxative is similar to otheranthraquinone-containing herbal preparations of leaves and fruits ofsenna, thelatex ofAloe vera, and the root of therhubarb plant.[28] Commercially, it is called "cascara sagrada" ('sacred bark' in Spanish), while in the traditionalChinook 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 ofR. catharticus as the favored laxative.[2] The historical interest in using cascara damaged native cascara populations during the 1900s due to overharvesting.[29]
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 causesvomiting and violentdiarrhea. 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] BotanistJ. 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 1–3grams (15–46 gr) dried bark, or 1–2.5grams (15–39 gr) powdered bark.[23]
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] 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 soilerosion.[22] Due to its bitter taste, cascara can be used to stop nail-biting by applying it to the fingernails.[22]
