Chapter 18 - Steroid Saponins and Sapogenins

Abstract

This chapter provides an overview of steroid saponins and sapogenins. Saponins have been isolated from plants; the complete structure of some of them is presented in the chapter. The structure of furostanol glycosides, lanatigoside, lanagitoside and “TFI” is also presented. A number of steroid saponins, such as parillin, gracillin, and dioscin have significant activity against various fungi and against termites. Neither the acylated saponins nor the free sapogenins have antifungal activity; this might be associated with their lesser solubility in water, but it would appear that structural features are important, because several cardiac glycosides are much less active than the saponins. Steroid saponins also have anti-tumour effects; thus, fractionation of an extract of Agave schottii Engelm, with activity against the Walker carcinoma, showed the activity to be associated with the saponins and especially with a galactoside of gitogenin. Isoplexigenin-C is identified as a secondary hydroxy-derivative of gitogenin by its conversion into the latter through the diacetoxy-mono-oxo-compound. Apart from the free amino-spirostans, five monoglycosides have been isolated from the same plant; four of them yield isojuribidine, the fifth yields isojuripidine on hydrolysis.