Amidine derivatives are highly effective against Trypanosoma evansi trypomastigotes

The in vitro effect of N,N'-diphenyl-4-R-benzamidine (where R = H, CN, Br, Cl, CH3, OCH3 and NO2) in three isolates of Trypanosoma evansi was studied. The compounds were solubilized in dimethysulphoxide (DMSO) and tested in a concentration range of 5 to 160 mu g/ml. The parasites were isolated from a horse, a dog and a coati. They were maintained in immunosuppressed rats, since they could not be cultured in vitro, and further purified through a d iethylaminoethanol (DEAE) column. The trypomastigotes obtained were mixed w ith different concentrations of the drugs and after incubation at 26 degree s C for 24 h, the remaining parasites were counted in a Neubauer chamber. T he percentage of inhibition was evaluated compared with the control, withou t the drugs, Most of the amidine derivatives showed high activity against t he three T. evansi isolates, but different patterns of sensitivity to the t ested compounds were observed. At least four compounds with Br, Cl, OCH3 an d NO2 as substituents, were much more effective than Berenil [4,4'-(diazoam ine)-dibenzamidine aceturate], the reference drug used, which is included i n the same chemical class of amidines.