''Dioscorea mexicana'', Mexican yam or ''cabeza de negro'' is a species of yam in the genus ''

Dioscorea ''Dioscorea'' is a genus of over 600 species of flowering plants in the family Dioscoreaceae, native throughout the tropical and warm temperate regions of the world. The vast majority of the species are tropical, with only a few species extending ...

''. ''Dioscorea mexicana'' is a caudiciform

dioscorea ''Dioscorea'' is a genus of over 600 species of flowering plants in the family Dioscoreaceae, native throughout the tropical and warm temperate regions of the world. The vast majority of the species are tropical, with only a few species extending ...

having either a partly to completely above-ground dome-shaped

caudex A caudex (plural: caudices) of a plant is a stem, but the term is also used to mean a rootstock and particularly a basal stem structure from which new growth arises.pages 456 and 695 In the strict sense of the term, meaning a stem, "caudex" is m ...

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 tog ...

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 San Luis Potosí (), officially the Free and Sovereign State of San Luis Potosí ( es, Estado Libre y Soberano de San Luis Potosí), is one of the 32 states which compose the Federal Entities of Mexico. It is divided in 58 municipalities and i ...

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 Cos ...

. It is notable for its production of

diosgenin Diosgenin, a phytosteroid sapogenin, is the product of hydrolysis by acids, strong bases, or enzymes of saponins, extracted from the tubers of ''Dioscorea'' wild yam species, such as the Kokoro. The sugar-free (aglycone) product of such hydrolys ...

, 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 unr ...

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 required ...

s such as

progesterone Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the m ...

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 su ...

developed the extraction and manufacture of

hormones A hormone (from the Ancient Greek, Greek participle , "setting in motion") is a class of cell signaling, signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and beh ...

from ''D. mexicana'' at

Syntex Laboratorios Syntex SA (later Syntex Laboratories, Inc.) was a pharmaceutical company formed in Mexico City in January 1944 by Russell Marker, Emeric Somlo, and Federico Lehmann to manufacture therapeutic steroids from the Mexican yams called ''cabe ...

. 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. Russel ...

'' instead, as this variety has a higher diosgenin content.

References

External links

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