CARDENOLIDE UND BUFADIENOLIDE (= CARDADIENOLIDE)

Summary

After a short historical and chemical introduction the taxonomic distribution of cardenolides and bufadienolides in plants is summarized (2 tables).

Cardiac glycosides are restricted to Angiosperms; this indicates some special features in steroid metabolism of flowering plants. Within Angiosperms cardiac glycosides occur in a highly erratic manner. They may help the taxonomist in the understanding of critical aggregates (e. g. Urginea maritima, Strophanthus sarmentosus, Acokanthera) and in the study of the difficult apocynaceous–asclepiadaceous complex.

Cardiac glycosides and related toxic secondary metabolites are almost certainly ecologically important plant constituents. This should never be forgotten when taxonomic conclusions are drawn from their chemical and distributional patterns.

In general, a combined chemical and botanical approach will always result in a better understanding of nature. It will depend, however, on the classes of plant constituents and the plant taxa concerned whether phytochemistry or botany profits more by such a collaboration. In the case of cardiac glycosides it seems to be phytochemistry which has more to learn from taxonomy than vice versa. Hypothesis needed for structural and biogenetic experiments are often inspired by taxonomic concepts. The success of many of these hypothesis, of course, may be accepted as indirect proof of the naturelness of many parts of our present–day botanical systems.