Dioscorea mexicana

rdf:langString Dioscorea mexicana

rdf:langString Mexican yam

rdf:langString Scheidw.

rdf:langString Dioscorea

rdf:langString mexicana

rdf:langString *Dioscorea macrostachya (Benth.) *Dioscorea macrophylla (M.Martens & Galeotti) *Dioscorea deppei (Schiede ex Schltdl.) *Dioscorea bilbergiana (Kunth) *Dioscorea leiboldiana (Kunth) *Dioscorea propinqua (Hemsl.) *Testudinaria cocolmeca (Procop.) *Dioscorea astrostigma (Uline) *Dioscorea macrostachya var. sessiliflora (Uline) *Dioscorea tuerckheimii (R.Knuth) *Dioscorea anconensis (R.Knuth) *Dioscorea deamii (Matuda) *Dioscorea mexicana var. sessiliflora ( Matuda) *Testudinaria macrostachya ( G.D.Rowley)

rdf:langString Dioscorea mexicana, Mexican yam or cabeza de negro is a species of yam in the genus Dioscorea. Dioscorea mexicana is a caudiciform dioscorea having either a partly to completely above-ground dome-shaped caudex with a thick, woody outer layer up to 3 feet (90 cm) in diameter and 8–10 inches (20 to 25 cm) in height. The caudex of D. mexicana is divided into regular polygonal plates that become protuberant with age, and separated by deep fissures. The vigorous annual vines which may reach 30 feet (9 m) long before dying back in winter, that grow up from the caudex, bear heart-shaped leaves. Dioscorea mexicana ranges from the state of San Luis Potosí in northeastern Mexico south to Panama. It is notable for its production of diosgenin, which is a precursor for the synthesis of hormones such as progesterone. Russell Marker developed the extraction and manufacture of hormones from D. mexicana at Syntex. Later the Mexican barbasco trade focused instead on Dioscorea composita instead, as this variety has a higher diosgenin content.