Dioscorea mexicana

Marker s synthesis was initially based on sarsasapogenin as starting material from root extracts of the Mexican sarsaparilla plant (Smilax aristolochiaefolia), and later on diosgenin. Diosgenin is found as the 3-glycoside (dioscin) in numerous Liliaceae and Dioscoreaceae species, and may be extracted with ethanol from the air-dried rhizomes of Dioscorea tokoro, Dioscorea macrostachya, Dioscorea mexicana, Dioscorea floribunda and Dioscorea composita (Barbasco). The extract is evaporated and heated with dilute hydrochloric or sulfuric acid to cleave the glycosidic bond. Subsequently, diosgenin is filtered off and used as such for the synthesis of steroid hormones. 

Initially, Marker wanted to obtain diosgenin from the roots of the inedible yam Dioscorea mexicana, which grows wild in Mexico (Fig. 6.13). [27] Parke-Davis Co. and other pharmaceutical companies did not want to engage in supply of plant material from Mexico for political and reliability reasons. Thus, Marker quit his position at the Pennsylvania State University in 1943, travelled to Mexico, rented a small house and explored the jungle in the mountains of Veracruz with a mule. 

Dioscorea mexicana (Mexican yam orcabeza de negro) is a species of yam in the genus (Dioscorea). It has either a partly to completely above-ground dome-shaped caudex with a thick, woody outer layer, which resembles the shell of a tortoise. It is divided into polygonal plates that are scored by deep furrows. 

Alkaloids are known in a few members of the family. Tests on 45 samples which included 37 species resulted in three positives in plants known to be alkaloidal (Dioscorea dumetorum, D. hispida, D. alaia) and in two of 13 other unidentified Dioscorea species. The remainder were negative Dioscorea abyssinica, D. alata, D. batatas, D. bucha-nanii, D. bulbifera, D. composita, D. cotinifolia, D. doryophora, D. dregeana, D. esculenla, D. hemicrypta, D. hirtiflora, D. mexicana, D. pentaphylla, D. quartiniana, D. retusa, D. sylvatica, D. trifida, Tamus edulis. 

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