Dioscorea composita, or barbasco, is a species of yam in the family Dioscoreaceae. It is 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 Marker developed the extraction and manufacture of hormones from D. mexicana at Syntex, starting the trade of D. composita in Mexico. Marker also discovered that the composita variety had a much higher content of diosgenin than the mexicana variety, and therefore it came to replace the latter in the production of synthetic hormones.

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