N-N-ALKYL-3,4-DIHYDROXYBENZAMIDES AS INHIBITORS OF THE TRYPANOSOME ALTERNATIVE OXIDASE - ACTIVITY INVITRO AND INVIVO

On the basis of our previous demonstration of the high inhibitory acti vity of a series of p-n-alkyloxybenzhydroxamic acids and n-alkyl ester s of 3,4-dihydroxybenzoic acid against the trypanosome alternative oxi dase in a cell-free mitochondrial preparation of Trypanosoma brucei br ucei, we synthesized a series of N-n-alkyl-3,4-dihydroxybenzamides for evaluation as inhibitors of this enzyme. This class of compounds was selected with the expectation of their having similar inhibitory activ ity to but greater solubility than the esters and hydroxamic acids not ed above and greater resistance to serum hydrolases in vivo. We predic ted that such properties would allow an inhibitor of the trypanosome a lternative oxidase to be coadministered with glycerol as a means of pr oviding treatment for infections by African trypanosomes. As expected, such benzamides were both more soluble and more stable, some being mo re active against the target enzyme than the corresponding ester. One, N-n-butyl-3,4-dihydroxybenzamide, was selected for evaluation in vivo against T. brucei brucei. When combined with glycerol, this benzamide was found to be curative. A regimen wherein 450 mg of N-n-butyl-3,4-d ihydroxybenzamide per kg and 15 g of glycerol per kg were given hourly in three divided doses cured 17 of 19 mice with established T. brucei brucei infections. This combination is more active in vivo than any o ther designed to block simultaneously both the unique respiratory elec tron transport system and the anaerobic glycolytic pathways of these p athogenic protozoa.