Proposed mechanism for the trypanocidal activity of the benzyl and ethyl esters of NPOx. B-NPOx and Et-NPOx would diffuse through the cellular membrane of T. cruzi, where they would be hydrolyzed by intracellular aliphatic and aromatic carboxyl esterases to give NPOx, which is a selective and competitive inhibitor of HADH-isozyme II. Et-NPOx would also give the inactive ethyl alcohol, whereas B-NPOx would give benzyl alcohol, which is a well know antimicrobial agent that also exhibits trypanocidal activity (as we demonstrated here). B-NPOx would therefore exhibit dual trypanocidal activity resulting from NPOx and benzyl alcohol. Furthermore, the lipophilicity of B-NPOx was found to be 1.76-fold greater than that of Et-NPOx, which would allow it to penetrate more effectively into T. cruzi than Et-NPOx to give a higher level of trypanocidal activity.