144 



TERPENOIDS AND STEROIDS 



The usual basic nucleus is as follows: 



Other substituent groups may be present, for example additional hydroxy groups at C-1, 

 11, 12, 16, and 19. The sugars are always linked at C-3. Some members have an aldehyde 

 group rather than a methyl group at C-19, and many have a.cis A/B ring fusion. The so- 

 called scilladienolides of squill and hellebore have a six-membered lactone ring: 



Ci, 



The cardiac glycosides are found in several quite unrelated plant families such as 

 Apocyanaceae, Liliaceae, Moraceae, and Ranimciilaceae . Plants containing them have 

 been used since prehistoric times as arrow and ordeal poisons. The glycosides have a 

 specific cardiotonic effect. The aglycones are poisonous but have no specific effect on 

 heart muscle. 



The chief commercial source is the genus Digitalis {i2in\\\y Scrophulariaceae). Sev- 

 eral species of this genus are used, and active material is extracted from seeds, leaves 

 and roots. It will be recalled that this same genus is the source of the steroid saponin, 

 digitonin. 



By the usual methods of preparation some degradation occurs, both by enzymatic 

 and non-enzymatic hydrolysis of some of the sugar residues and ester groups which may 

 be present. Thus what were originally believed to be the three active glycosides of Digi- 

 talis, digitoxin, gitoxin, and digoxin are known to be derived from the actual natural prod- 

 ucts (the digilanides, A, B, and C) by loss of a glucose residue and an acetyl group. The 

 same aglycone or genin may be present in different plants but joined with different sugars. 

 Structures of some of the rare sugar components are given below: 



CHO 



H 



CH39--H 



HO- 

 H 



OH 



H 

 OH 



CH 



CHO 



CH. 



CHO 



CH- 



CHO 



H- 



HO- 

 H- 



H 



•OCH, 

 •H 

 -OH 



CH, 



D-digitalose 



D-cymarose 



D-digitoxose 



D-sarmentose 



