Which climbing plant is the source of diosgenin, historically used to synthesize steroid medicines? Mexican yam is the answer.
Mexican yam is the common name for Dioscorea mexicana, a vigorous climbing vine native from Mexico through parts of Central America. Its annual vines can grow many metres long from a large, woody, above-ground caudex. The plant is notable for producing diosgenin, a steroidal sapogenin obtained from compounds in its underground storage organs.
Diosgenin itself is not progesterone or estrogen. Rather, chemists can convert it through semisynthetic processes into steroid compounds including progesterone, cortisone, and pregnenolone. In the twentieth century, this chemistry helped make steroid medicines more affordable and contributed to the industrial development of hormonal drugs.
A historical complication is that Mexican yam was not the only important source. Russell Marker initially developed hormone production from D. mexicana, but the Mexican barbasco industry later relied heavily on Dioscorea composita because it generally contained more diosgenin. Thus “Mexican yam” correctly identifies the plant in the question, while “wild yam” can refer to several related species.