purshiana

Purshiana refers to the plant species Rhamnus purshiana, commonly known as cascara buckthorn or cascara sagrada. It is a flowering shrub or small tree in the family Rhamnaceae, native to western North America, from British Columbia to northern California. The species epithet purshiana honors the 19th-century botanist Frederick Traugott Pursh.

Rhamnus purshiana typically grows as a shrub or small tree reaching several meters in height. It has simple, oval to elliptic leaves, small inconspicuous flowers, and clusters of dark berries. The bark, particularly the inner corky layer, is thick and has long been harvested for medicinal use. Harvesting is traditionally done from wild trees but may be cultivated.

The dried inner bark contains stimulant laxative constituents, notably anthraquinone glycosides such as cascarin and related compounds (including emodin). Cascara bark has been used in Indigenous medicine and later in Western herbal practice to promote bowel movements. In modern use, cascara is often found in laxative products and is typically administered for short-term relief of constipation. Long-term or excessive use can cause electrolyte imbalance, dehydration, and dependence, and may lead to adverse effects such as abdominal pain or melanosis coli; safety concerns restrict use in certain populations, including pregnant individuals and young children. Product strength and quality vary, and regulatory guidance on marketing claims varies by country.