Cao Wu

Aconitum kusnezoffii Reichb. (Ranunculaceae), Kusnezoff monkshood, is the principal source of Cao Wu, "wild aconite," a perennial herb 70-150 cm tall native to northeastern China, Mongolia, Korea, and the Russian Far East in forest margins and meadows. The plant develops paired tuberous roots, one persistent and one regenerating; the dried lateral or main tuber is the medicinal portion. Stems are erect, glabrous, and sparsely branched above. Leaves are alternate, palmately deeply 3-5 parted into narrow, sharply incised lobes, dark green and glossy above. The striking dark purple to violet-blue flowers are borne in terminal racemes 10-30 cm long in late summer; each flower has the characteristic helmet-shaped upper sepal 1.5-2.5 cm long enclosing two hooked nectary petals and numerous stamens, with a follicle fruit ripening to release flat-winged seeds. The root contains highly toxic diterpenoid alkaloids (aconitine, mesaconitine, hypaconitine). In TCM, processed Cao Wu dispels wind-damp, warms the channels, and powerfully alleviates pain; raw root is strictly prohibited internally.