Cardenolide sequestration

Mebsa D., Reussa E., and Schneider M. (2005). Studies on the cardenolide sequestration in African milkweed butterflies (Danaidae). Toxicon 45 581-584. 

A classical example of sequestration is the monarch butterfly Danaus plexip-pus (Danainae) which feeds on leaves oiAsclepias curassavica (Asclepiadaceae) and sequesters cardenolides such as calotropin (158) (Fig. 29). This molecule was shown to afford the butterfly an efficient protection against birds [150-152]. It was also demonstrated that its resistance to cardiac glycosides is due to a single amino acid mutation in the ouabain-binding site of the Na+/K+ ATPase [153,154]. 

Larvae of Inoplnatus emerge as major sequestrators of cardenolides primarily because their hemolymph, which is present in a relatively large volume, effectively sequesters high concentrations of polar cardenolides (26). Cardenolide excretion largely reflects loss of these steroids as components of the larval exuviae, the concentration of these compounds becoming relatively stable after pupal ecdysis. These steroids are ubiquitously distributed in the adult moth, having been derived primarily from the rich cardenolide pool in the larval blood. 

C. procera R.Br and toxicity F. Briischweiler et at., Helv. Chim. Acta 52, 2086 (1969). Revised structure eidem, ibid. 2276. Sequestration by larvae of Monarch butterfly Danaus plexippus L. 1. N. Sieber et al.. J. Chem. Ecol. 6, 321 (1980). Quantitative analysis of cardenolides in latex and leaves of C procera eidem. Phytochemistry 21, 2343 (1982). Biosynthesis of labelled compd M. S. Lee, J. N. Sieber, ibid. 22, 923 (1983). 

The observed switch of Oreina leaf beetles from their original mode of defense (i. e., antogenous production of cardenolides) to host-derived defense (i.e., sequestration of PAs) intensified the discussion about the evolution of host plant affiliation and chemical defense in leaf beetles [108,115]. Evolutionary scenarios favor the role of PAs as efficient defensive compound. Recently, it was... 

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