Structure-function analysis of antimicrotubule dinitroanilines against promastigotes of the parasitic protozoan Leishmania mexicana.

Although leishmaniasis is a major tropical disease, the currently available drugs are toxic and inadequate. We show that the antimicrotubule herbicide trifluralin has antileishmania activity. The present study aimed at deducing the relationship between the structure of the molecule and its antiprotozoan activity. Nine dinitroanilines, all of which were analogs of trifluralin, were compared. We found that pendimethalin was 2.5-fold more potent than trifluralin, and the higher efficacy may be correlated with molecular structural features that increase the accessibility to one nitro group. This association was further supported by molecular modeling. Moreover, trifluralin samples from two sources differed in their activities by more than threefold, and gas column chromatography showed that impurities were present in the more potent sample.