Synthesis, antiprotozoal and cytotoxic activities of new N-(3,4-dimethyl-5-isoxazolyl)-1,2-naphthoquinone-4-amino derivatives

Three derivatives of N-(3,4-dimethyl-5-isoxazolyl)-1,2-naphthoquinone-4-amino ( 1), a compound which exhibits significant activity against Trypanosoma cruzi and Plasmodium falciparum but with cytotoxicity toward murine L-6 cells, were synthesized with the aim of ameliorating its cytotoxicity. The in vitro antiprotozoal and cytotoxic activities of the synthesized compounds were evaluated against T. cruzi, Trypanosoma brucei rhodesiense, P. falciparum and murine L-6 cells. The hydroxymethyl ( 2) and the oxime ( 3) derivatives were active against T. cruzi, with IC 50 values in a range comparable to those of 1 (IC 50: 0.65 μg/ml) and benznidazole (IC 50: 0.56 μg/ml) while the carboxymethyloxime ( 4) was inactive. Compounds 2 and 3 were cytotoxic toward L-6 cells, with IC 50 values identical to that of 1 (IC 50: 0.50 μg/ml). The results did not support the suggestion that 2 and 3 may be used as prodrugs of 1.