Huang Yao Zi

Huang Yao Zi is the tuberous rhizome (bulbil) of Dioscorea bulbifera L. (Dioscoreaceae), the air-potato yam, a perennial twining herbaceous vine 5-30 m long native to tropical Asia and Africa and widespread across southern China. The slender, smooth, left-twining stems arise from a large brown irregular subterranean tuber and bear conspicuous aerial bulbils 2-10 cm in diameter at the leaf axils. Alternate, long-petioled, broadly cordate leaves are 5-15 cm long with palmate venation. Small, fragrant, greenish-white flowers are borne in pendulous axillary spikes. The harvested tuber is sliced and dried, appearing as flat, brownish-yellow discs with a hard texture and bitter taste. In TCM the rhizome cools blood, resolves toxin, and softens hardness, used for goitre, lymphadenopathy, sore throat, and abscesses. The herb is hepatotoxic, especially with prolonged use or in raw form; modern guidance limits dosing duration and recommends processed material.