New Structures, Spectrometric Quantification, and Inhibitory Properties of Cardenolides from Asclepias curassavica Seeds
Rubiano-Buitrago P, Pradhan S, Paetz C and others. Molecules (Basel, Switzerland), December 2022.
Read the paper Free to read · doi:10.3390/molecules28010105
What this paper is about
Milkweed seeds are eaten by lygaeid bugs, which tolerate cardenolides better than any other known insect. If those bugs drive the plant to keep inventing new toxins, the seeds are where the newest ones should be.
This study profiled the cardenolides in tropical milkweed seed, reporting new structures and measuring how strongly each inhibits the sodium-potassium pump.
Summarised here from the abstract below. Not the authors’ words.
Abstract
Cardiac glycosides are a large class of secondary metabolites found in plants. In the genus Asclepias, cardenolides in milkweed plants have an established role in plant-herbivore and predator-prey interactions, based on their ability to inhibit the membrane-bound Na+/K+-ATPase enzyme. Milkweed seeds are eaten by specialist lygaeid bugs, which are the most cardenolide-tolerant insects known. These insects likely impose natural selection for the repeated derivatisation of cardenolides. A first step in investigating this hypothesis is to conduct a phytochemical profiling of the cardenolides in the seeds. Here, we report the concentrations of 10 purified cardenolides from the seeds of Asclepias curassavica. We report the structures of new compounds: 3-O-β-allopyranosyl coroglaucigenin (1), 3-[4'-O-β-glucopyranosyl-β-allopyranosyl] coroglaucigenin (2), 3'-O-β-glucopyranosyl-15-β-hydroxycalotropin (3), and 3-O-β-glucopyranosyl-12-β-hydroxyl coroglaucigenin (4), as well as six previously reported cardenolides (5-10). We test the in vitro inhibition of these compounds on the sensitive porcine Na+/K+-ATPase. The least inhibitory compound was also the most abundant in the seeds-4'-O-β-glucopyranosyl frugoside (5). Gofruside (9) was the most inhibitory. We found no direct correlation between the number of glycosides/sugar moieties in a cardenolide and its inhibitory effect. Our results enhance the literature on cardenolide diversity and concentration among tissues eaten by insects and provide an opportunity to uncover potential evolutionary relationships between tissue-specific defense expression and insect adaptations in plant-herbivore interactions.
Abstract reproduced from the published paper, which is licensed CC BY. Copyright remains with the authors.
Key terms
Milkweeds in this paper
- Tropical Milkweed Asclepias curassavica
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title = {New Structures, Spectrometric Quantification, and Inhibitory Properties of Cardenolides from Asclepias curassavica Seeds (listing)},
author = {{Milkweed USA}},
year = {2026},
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