Bai Qian

Cynanchum stauntonii (Decne.) Schltr. ex H. Lév. (Apocynaceae, formerly Asclepiadaceae) is a perennial herb native to China and Japan, growing 30-80 cm tall from slender creeping rhizomes, with erect or slightly twining stems, opposite linear-lanceolate leaves, and small yellow-white flowers in axillary cymes. The medicinal Bai Qian is the dried rhizome with its attached roots, harvested in spring or autumn. The rhizome is thin, cylindrical, jointed with prominent nodes, pale yellow externally, with numerous fine wiry roots; it contains C21 steroidal glycosides (cynanchotoxin and related compounds), triterpenes, and alkaloids. In traditional Chinese medicine, Bai Qian is acrid, sweet, and slightly warm, entering the lung channel; it descends rebellious qi, transforms phlegm, and stops cough, used for cough and wheezing with copious phlegm regardless of whether the pattern is hot or cold. It is paired with Qian Hu in classical formulas for phlegm-stagnation cough.