Cynanchum atratum Identity & Plant Part
The botanical entity is Cynanchum atratum Bunge, a perennial of the Apocynaceae with opposite leaves and small dark purple flowers. The part used is the root together with the short rhizome it grows from, a clump of fine, brittle roots. Stems, leaves and seeds are not part of this ingredient.
The Chinese trade name bai wei is also applied to a second species, Cynanchum versicolor, and another root called bai qian from a different genus is sometimes confused with it. Reading the botanical name is therefore the reliable check. Cynanchum atratum root carries C21 steroidal glycosides and a small amount of volatile oil, named only as families.












