Rhamnus purshiana is the name of one of the native species of buckthorn that is also a powerful plant-based laxative.
 It is different from cascara sagrada tea, a powerful plant-based laxative. 
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. 
