Mexican yam
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''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 In geometry, a polygon () is a plane figure that is described by a finite number of straight line segments connected to form a closed ''polygonal chain'' (or ''polygonal circuit''). The bounded plane region, the bounding circuit, or the two to ...
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 Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...
south to
Panama Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Co ...
. It is notable for its production of diosgenin, which is a
precursor Precursor or Precursors may refer to: * Precursor (religion), a forerunner, predecessor ** The Precursor, John the Baptist Science and technology * Precursor (bird), a hypothesized genus of fossil birds that was composed of fossilized parts of u ...
for the synthesis of
hormone A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are require ...
s such as progesterone.
Russell Marker Russell Earl Marker (March 12, 1902 – March 3, 1995) was an American chemist who invented the octane rating system when he was working at the Ethyl Corporation. Later in his career, he went on to found a steroid industry in Mexico when he s ...
developed the extraction and manufacture of hormones from ''D. mexicana'' at Syntex. Later the
Mexican barbasco trade The Mexican barbasco trade was the trade of the diosgenin-rich yam species '' Dioscorea mexicana'', ''Dioscorea floribunda'' and ''Dioscorea composita'' which emerged in Mexico in the 1950s as part of the Mexican steroid industry. The trade consi ...
focused instead on ''
Dioscorea composita ''Dioscorea composita'', or barbasco, is a species of yam in the genus ''Dioscorea'', native to Mexico. It is notable for its role in the production of diosgenin, which is a precursor for the synthesis of hormones such as progesterone. Russell ...
'' instead, as this variety has a higher diosgenin content.


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mexicana Flora of Central America Flora of Mexico Plants described in 1837 Caudiciform plants {{monocot-stub