Cascara sagrada (also known as wahoo) is a small, deciduous tree native to the Pacific coast from northern California to British Columbia. A member of the buckthorn family, cascara grows up to 8 meters in height and has thin, ovate leaves, which are 5 to 15 centimeters long, with pronounced veins, serrated edges, and pointed tips. Cascara flowers in spring, displaying clusters of tiny, greenish-yellow flowers, which eventually give way to spherical, berrylike fruit. The fruit, which changes in color from red to black as it ripens, is about 12 millimeters in diameter, containing two or three pea-sized seeds. The plant has a distinctive reddish colored bark, which is used for health purposes.
Cascara bark contains a number of anthracene derivatives (designated as cascarosides A through F). These compounds influence the motility of the colon, inhibiting stationary contractions while stimulating propulsive contractions. This accelerates intestinal passage, reducing liquid absorption for softer stools. The fresh bark contains free anthrones, which can cause severe vomiting, and possibly spasms. The bark must be stored for a year or artificially aged with heat in order to neutralize these compounds.
The recommended daily dosage for cascara is for dried bark, extracts, or preparations providing 20 to 30 mg of anthracene derivatives, calculated as cascaroside A. The correct individual dosage is the smallest dosage necessary to maintain soft stools. Cascara should not be used for an extended period of time (1-2 weeks) without medical supervision. It should not be used during pregnancy or lactation, by children under 12, or by people suffering from intestinal inflammation or abdominal pain of unknown origin. Some individuals experience cramp-like side effects, which may require reduction of dosage. Cascara overdose can cause electrolyte and fluid imbalance.