Trypanocidal activity of guaianolide obtained from Tanacetum parthenium (L.). Schultz-Bip. and its combinational effect with benznidazole

In the present study, we evaluated the in vitro antiprotozoal activity of a guaianolide (11,13-dehydrocompressanolide) isolated from Tanacetum part henium against Trypanosoma cruzi and investigated the possible combinational effect of guaianolide and benznidazole. The isolated compound was shown to be effective against T. cruzi, with IC50 values of 18.1 +/- 0.8 and 66.6 +/- 1.3 mu M against the multiplicative epimastigote and amastigote forms, respectively. The best results were obtained against trypomastigotes, with an EC50 of 5.7 +/- 0.7 mu M. The guaianolide presented no toxicity in LLCMK2 cells (CC50 of 93.5 mu M) and was 16.4-fold more selective for trypomastigotes. The study of the combinational effect of benznidazole and guaianolide revealed the presence of a synergistic effect against the epimastigote form and marginal additive effect against the trypomastigote form. Striking morphological changes were observed in epimastigotes treated with guaianolide, such as thinning and stretching of the cell body and flagellum and changes in the format of the cell body with apparent leakage of the cytoplasmic content in trypomastigote forms. The ultrastructural analysis of epimastigotes revealed the presence of membranes that involved organelles and formation of myelin-like figures. Flow cytometry revealed a cell volume reduction and decrease in mitochondrial membrane potential. However, no major changes in cell membrane integrity were found in the epimastigote form treated with guaianolide. (C) 2012 Elsevier GmbH. All rights reserved.