Synthesis and antileishmanial evaluation of 1-aryl-4-(4,5-dihydro-1H-imidazol-2-yl)-1H-pyrazole derivatives.

A series of 1-aryl-4-(4,5-dihydro-1H-imidazol-2-yl)-1H-pyrazoles (4a-g) and 5-amino-1-aryl-4-(4,5-dihydro-1H-imidazol-2-yl)-1H-pyrazoles (5a-g) were synthesized and evaluated in vitro against three Leishmania species: L. amazonensis, L. braziliensis and L. infantum (L. chagasi syn.). The cytotoxicity was assessed. Among the derivatives examined, six compounds emerged as the most active on promastigotes forms of L. amazonensis with IC(50) values ranging from 15 to 60 µM. The reference drug pentamidine presented IC(50)=10 µM. However, these new compounds were less cytotoxic than pentamidine. Based on these results, the more promising derivative 5d was tested further in vivo. This compound showed inhibition of the progression of cutaneous lesions in CBA mice infected with L. amazonensis relative to an untreated control.

Evaluation of thiosemicarbazones and semicarbazones as potential agents anti-Trypanosoma cruzi.

Synthetic thiosemicarbazones and semicarbazones were evaluated for their Trypanosoma cruzi trypomastigotes obtained from LLC-MK2 cell cultures. In general, thiosemicarbazone derivatives were most effective and among them the 4-N-(2'-methoxy styryl)-thiosemicarbazone was chosen, to compare the in vitro effect against amastigotes of T. cruzi lodged in mouse peritoneal and human macrophages. A potent trypanocidal effect was observed that was more pronounced against parasites internalized in human macrophages. A potential target for this compound was also evaluated by measuring the nitric oxide synthase activity through NADPH consumption. A significant decrease in enzyme activity was observed. In contrast to the cytotoxic effect observed with benznidazole, no macrophage toxicity was observed for any of the compounds, indicating that their activity was specific for the parasite forms investigated.