Solanum glaucophyllum Desf. is a calcinogenic plant growing wild mainly in South America, where its ingestion causes intoxication of grazing animals. Early work suggested that glycosides of various vitamin D3 sterols occur in minute concentrations in the plant leaves and are responsible for a calcinotic disease of cattle prevalent in Argentina and Brazil, with symptoms resembling vitamin-D intoxication. The vast literature on this topic describing chemical, toxicological, and physiological aspects has been extensively reviewed in the last decade (). A few communications reporting the occurrence of small amounts of other steroids such as p-sitosterol, diosgenin and solasodine, and also of phenolic derivatives (vide infra), have already been summarized (). Since this chapter is concerned with the in vitro production of metabolites in Solanum glaucophyllum, the naturally occurring steroidal derivatives which have been found to occur also in vitro will be treated preferentially in the following survey.
Distribution and Importance of Solanum glaucophyllum
Solanum glaucophyllum is a deciduous, rhizomatous shrub () growing wild typically in low-lying, wet land in the poorly drained eastern and central parts of the Buenos Aires province and in the northeastern provinces of Argentina (), as well as in the Matto Grosso region of Brazil, in Uruguay and Paraguay (), and in India (). Accordingly, the incidence of the toxicose is greatest in flooded areas having pastures of higher feeding value than drier areas (). The taxonomic keys available to identify Solanum glaucophyllum are summarized in Table “Identification of Solanum glaucophyllum”. The plant has an extensive and deep underground root system () which apparently confers considerable resistance to weed killers. Dispersal is probably by animals and birds that consume the berries or seeds. When a seedling is formed, vegetative propagation develops and a large array of Solanum glaucophyllum can thus be established. Fallen leaves retaining their toxicity for several months mix intimately with neighboring herbage on the underlying pasture (thus improving palatability) and are likely to be eaten accidentally by the grazing animal (). Extensive information on the growth habit, distribution, and ecology of Solanum glaucophyllum has been presented in detail ().
The economic relevance of Solanum glaucophyllum might be assessed in two ways: as the causal factor of the toxicosis of grazing cattle and, implicitly, as a potentially valuable source of vitamin D3 sterols and other steroids, the latter aspect being the main subject of this survey. Conversely, the calcinotic disease of livestock induced by Solanum glaucophyllum ingestion causes considerable economic losses to the cattle industry in Argentina and in Brazil () and measures for field control of the toxicosis have been studied (), including the possibility of removal of Solanum glaucophyllum from pastures, mechanical eradication, treatment with herbicides, or better drainage of the area ().
Solanum glaucophyllum is regarded as the main plant source of vitamin D3 sterols. Cultured in vitro, it affords calli and suspensions that display substantial la, 25-(OH)2D3 activity, and have also the ability to synthesize p-sitosterol, diosgenin and solasodine, although at low concentrations. Besides providing a potentially useful biotechnological approach at least for loc,25-(OH)2D3 production, this plant might constitute a highly interesting model for studying the in vitro metabolism of quite a large array of steroidal derivatives, and for evaluating the chemotaxonomic significance of their occurrence and distribution, both in vitro and in vivo. These studies are still in a very early phase and much work has yet to be done.
Selections from the book: “Medicinal and Aromatic Plants IV”, 1993.