Bai Yao Zi

Bai Yao Zi is the tuberous root of Stephania species, principally Stephania cepharantha and the closely related S. tetrandra, both perennial climbing vines of the family Menispermaceae native to southern China and adjacent parts of East Asia. The plant arises from a large, irregularly globose to elongate underground tuber that may weigh several kilograms in mature specimens and is the medicinally collected part. Slender, twining herbaceous stems climb to 2 to 4 metres, bearing alternate, peltate, broadly ovate to nearly round leaves with the petiole inserted within the blade and palmate venation radiating from that point. Small, dioecious, greenish-yellow flowers are borne in umbel-like cymes in the leaf axils, followed by small, flattened, red drupes. The plants favour shaded slopes, thickets, and forest margins from low elevations to about 1500 metres.