What is "rhamnus purshiana"

Cascara buckthorn \Cas"ca*ra buck"thorn`\ (Bot.) The buckthorn ( Rhamnus Purshiana) of the Pacific coast of the United States, which yields cascara sagrada. [Webster 1913 Suppl.] ||

chittamwood \chittamwood\ n.

1. a shrubby tree of the U. S. Pacific coast ( Rhamnus purshianus or Rhamnus purshiana), whose bark is the cascara sagrada, used as a mild cathartic or laxative.

   Syn: cascara, cascara buckthorn, bearberry, bearwood, chittimwood, Rhamnus purshianus.

2. a deciduous tree of SE U.S. and Mexico.

   Syn: false buckthorn, chittimwood, shittimwood, black haw, Bumelia lanuginosa.

3. a shrubby tree of southern U.S. ( Cotinus obovatus) having large plumes of feathery flowers resembling puffs of smoke; -- called also American smoke tree.

   Syn: American smokewood, Cotinus americanus, Cotinus obovatus.

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.