Comparative evaluation of the cytotoxic and apoptotic potential of Poecilocerus pictus and Calotropis gigantea.

Calotropis gigantea, the giant milkweed, is traditionally used for the treatment of cancer and in Ayurvedic medicine as an anti-helminthic, anti-pyretic, and anti-malarial agent. Poecilocerus pictus, an orthopteran insect, feeds on C. gigantea and both are known to possess cardiac glycosides. The increasing reports on the specific cytotoxicity of cardiac glycosides on human tumor cell lines led us to attempt characterization and comparative evaluation of cardenolides in both the insect and plant extracts for their anti-tumor and apoptotic potential.Chemical characterization using high-performance thin layer chromatography, ultraviolet and infrared spectra analysis confirmed the presence of cardiac glycosides, but differences in the components of the insect extract were indicative of biotransformation. The cytotoxicity studies revealed a more potent trend for the insect extract compared with the plant extract on A549 and COLO205 cells. There was a considerably lesser measure of toxicity on WI38 cells and peripheral blood lymphocytes, whereas B16F1 remained unaffected by both extracts. DNA ploidy analysis on COLO205 indicated that both extracts induced dose-dependent apoptosis. Therefore, both the insect and the plant extracts differentiate between human cancer cells and normal cells and exhibit species specificity. Further investigations are necessary to establish these extracts as promising lead candidates for anti-neoplastic activity.