Sequestration of Camptothecin, an Anticancer Alkaloid, by Chrysomelid Beetles
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Camptothecin (CPT), a monoterpene indole alkaloid, is a potent inhibitor of eukaryotic toposiomerase-I. Several derivatives of CPT are in clinical use against ovarian and lung cancers. CPT has been reported from several plant species belonging to the order Asterids, with the highest concentration in Nothapodytes nimmoniana (family Icacinaceae). In this paper, we report an intriguing observation of chrysomelid beetles (Kanarella unicolor Jacobby) feeding on the leaves of N. nimmoniana without any apparent adverse effect. LC-MS/MS analysis of the beetles indicated that 54.9% of the ingested CPT’s was recovered from the wings, followed by lesser amounts in the head and abdomen. LC-HRMS analysis revealed that most of the CPT in the insect body was in the parental form available in the plants without any major metabolizable products, including sulfated and glucuronilated forms. The mechanism by which the beetles are able to tolerate substantially high levels of CPT in their body tissue is under investigation.
Key WordsSequestration Anti-cancer Alkaloid Camptothecin Chrysomelid beetles Topoisomerase I
We thank Prof. C. A. Virakthamath and Dr. K. Chandrashekara, Department of Entomology and School of Ecology and Conservation, University of Agricultural Sciences, Bangalore for help in identification of the beetle.
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