Cardenolide levels in milkweeds?

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  • #14507


    Cardenolides are the poisonous chemicals in milkweeds that Monarch caterpillars store up to make themselves unattractive to predators.

    But exactly how poisonous are the various milkweeds? Discrepancies in the amounts of Cardenolides reported occoured in another discussion (

    So what figures have you seen reported for cardenolides? Post your references here and let’s see if we can find some sort of consensus.

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  • #25555


    Wow Darren!! All I can say is, I wish I had done well in Chemistry at school!!! most of this stuff goes way over my head. I can see this really is your subject of choice!



    Monarch butterflies sequester cardenolides from their larval host plants in the milkweed genus Asclepias for use in defense against predation. Of 108 Asclepias species in North America, monarchs are known to feed as larvae on 27. Research on 11 of these has shown that monarchs sequester cardenolides most effectively, to an asymptote of approximately 350 ug/0.1 g dry butterfly, from plants with intermediate cardenolide contents rather than from those with very high or very low cardenolide contents.

    Asclepias species (cardenolides ug/0.1g)

    A.erosa (79-2102)
    A.eriocarpa (102-919)
    A.vestita (88-1718)
    A.californica (9-199)
    A.cordifolia (19-238)
    A.speciosa (19-344)
    A.fascicularis (2-59)

    A.viridis (FL) (148-972)
    A.asperula (TX) (341-1616)
    A.viridis (LA) (95-433)
    A.humistrata (FL) (71-639)

    A.syriaca (4-229)

    Evolutionary and ecological implications of cardenolide sequestration in the monarch butterfly. S. B. Malcolm and L. P. Brower. Cellular and Molecular Life Sciences, Volume 45, Number 3, 284-295. retrieved from



    In this paper the authors identified 28 different cardenolides in A.fruticosa (aka ‘swan plant’ G.fruticosus). So it is not just a question of ‘how much cardenolide’ but also ‘which ones’? What makes this really interesting is that the ratios of these different cardenolides to each other makes a “fingerprint” which allows researchers to analyse a monarch and be able to determine which host-plant species it has been feeding on, and from that estimate where it came from!

    Rapid, quantitative HPLC analysis of Asclepias fruticosa L. and Danaus plexippus L. cardenolides. Henri W. Groeneveld, Harko Steijl, Bert Berg and Jopie C. Elings. Journal of Chemical Ecology Volume 16, Number 12, 3373-3382, retrieved from



    Variation in gross cardenolide concentration of the mature leaves of 85 Asclepias californica plants collected in four different areas of California is a positively skewed distribution ranging from 9 to 199 ug of cardenolide per 0.1 g dry weight with a mean of 66 ug/0.1 g.

    Plant-determined variation in cardenolide content and thin-layer chromatography profiles of monarch butterflies,Danaus plexippus reared on milkweed plants in California. L. P. Brower, J. N. Seiber, C. J. Nelson, S. P. Lynch, M. P. Hoggard and J. A. Cohen. Journal of Chemical Ecology Volume 10, Number 12, 1823-1857 retrieved from



    This paper is the fourth in a series on cardenolide fingerprints of monarch butterflies (Danaus plexippus, Danainae) and their host-plant milkweeds (Asclepiadaceae) in the eastern United States. Cardenolide concentrations of Asclepias humistrata plants from north central Florida ranged from 71 to 710 ?g/0.1 g dry weight, with a mean of 417 ?g/0.1 g. Monarchs reared individually on these plants contained cardenolide concentrations ranging from 243 to 575 ?g/0.1 g dry weight, with a mean of 385 ?g/0.1 g. Cardenolide uptake by butterflies was independent of plant concentration, suggesting that sequestration saturation occurs in monarchs fed cardenolide-rich host plants. Thinlayer chromatography resolved 19 cardenolides in the plants and 15 in the butterflies. In addition to humistratin,A. humistrata plants contained several relatively non-polar cardenolides of the calotropagenin series which are metabolized to more polar derivatives in the butterflies. These produced a butterfly cardenolide fingerprint clearly distinct from those previously established for monarchs reared on otherAsclepias species. In emetic assays with the blue jay,Cyanocitta cristata, the 50% emetic dose (ED50) per jay was 57.1 ?g, and the average number of ED50 units per butterfly was 13.8, establishing that this important south eastern milkweed produces highly emetic, chemically defended monarchs. Our data provide further support for the use of cardenolide fingerprints of wild-caught monarchs to make ecological predictions concerning defence against natural enemies, seasonal movement and larval host-plant utilization by monarch butterflies during their annual cycle of migration, breeding and overwintering.

    Cardenolide content, emetic potency, and thin-layer chromatography profiles of monarch butterflies,Danaus plexippus, and their larval host-plant milkweed,Asclepias humistrata, in Florida. Ronald A. Martin, Steven P. Lynch, Lincoln P. Brower, Stephen B. Malcolm and Tonya Van Hook. Chemoecology Volume 3, Number 1, 1-13. retrieved from



    Monarch Lab have an excellent article on the subject:



    “We now know that the cardenolide contents of different milkweeds vary quantitatively, qualitatively and spatially, both within and among species and we are starting to appreciate the implications of such variation.”

    Malcolm, Stephen B. (2005). Milkweeds, monarch butterflies and the ecological significance of cardenolides. Chemoecology Volume 5, Numbers 3-4, 101-117 retrieved from



    A.curassavica 563-2608 ug/g
    A.incarnata 0-46 ug/g

    (ug/g = microgram per gram)

    Cardenolides were extracted from harvested leaf samples by solid phase extraction and analyzed by high performance liquid chromatography (HPLC) using the methods of Wiegrebe and Wichtl (1993) as modified by Malcolm and Zalucki (1996). Mean foliar cardenolide concentrations for herbivore-free control plants harvested throughout the experiment were A. curassavica 1421 ug/g and A. incarnata 0 ug/g

    Density-Dependent Reduction and Induction of Milkweed Cardenolides by a Sucking Insect Herbivore. Journal of Chemical Ecology Volume 30, Number 3, 545-561. Martel, John W. and Malcolm, Stephen B. retrieved from

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