Bis-pyrazolines: Synthesis, characterization and antiamoebic activity as inhibitors of growth of Entamoeba histolytica

The cyclization of chalcone with N-4 substituted thiosemicarbazides under basic condition led to the formation of new compounds, thiocarbamoyl bis-pyrazoline derivatives. The structure of the compounds were elucidated by UV, IR, H-1 NMR, C-13 NMR and ESI-MS spectral data and thermogravimetric analysis, and their purities were confirmed by elemental analyses. The antiamoebic activity of these complexes was evaluated by microdilution method against HM1:1MSS strain of Entamoeba histolytica and the results were compared with the standard drug, metronidazole. Structure-activity relationship shows that the compound with aromatic substituents at the thiocarbamoyl group was more active than those with the cyclic groups. However, it was clear from the IC50 values that the compounds 15 and 20 are more active and both showed a structural resemblance having an electron withdrawing groups attached to the phenyl ring. MTT assay showed that all the compounds are nontoxic to human kidney epithelial cell line. (C) 2007 Elsevier Masson SAS. All rights reserved.