Abstract
Midgut and fat body homogenates of monarch butterfly larvae,Danaus plexippus L. (Lepidoptera:Danaidae), were examined for microsomal monooxygenase activity usingp-chloro-N-methylanilineN-demethylation and for the ability to metabolize a milkweed (Asclepias spp.) cardenolide (C23 steroid glycoside), uscharidin. All homogenates tested had bothN-demethylation and uscharidin biotransformation activities. Both transformations required NADPH. The monooxygenase inhibitors sesamex, SKF525A, and carbon monoxide inhibitedN-demethylation but not uscharidin biotransformation. Subsequent subcellular fractionation revealed the uscharidin biotransformation occurs in the soluble fraction and not the microsomal fraction, whileN-demethylation occurs in the microsomal fraction and not the soluble fraction. The larval NADPH-dependent microsomal monooxygenase apparently is not involved in the metabolism of uscharidin.
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Marty, M.A., Krieger, R.I. Metabolism of uscharidin, a milkweed cardenolide, by tissue homogenates of monarch butterfly larvae,Danaus plexippus L.. J Chem Ecol 10, 945–956 (1984). https://doi.org/10.1007/BF00987975
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DOI: https://doi.org/10.1007/BF00987975