Comparative Amoebacidal Activity of Some Compounds Related to Emetine.

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Abstract
Members of 2 series of compounds were tested against cultures of Entamoeba histolytica grown with Escherichia coli. In fixing amebacidal endpoints, records were made of bacterial populations, oxidation reduction potentials, and pH following 48-hr, tests in liver-egg yolk infusion. Emetine and a strongly antibacterial agent, aureomycin, also were included for reference, the latter as a check in the event that any of the exptl. series should prove antibacterial and thus raise a question about their direct or indirect amebacidal action. In the series of 4 phenylalkylamides of phenylalkylaminoisovaleric acids, alpha_methyl-beta-hydroxy_gamma_gamma''_bis(beta-phenyl-ethylamino)-N-(beta-phenylethyl)-isovaleramide dihydrochloride proved amebacidal at 200 ug./ml. which represented an activity 10 times greater than in the case of 3,4-dimethoxy substitution of the phenyl radicals. In this series the bis-substituted phenylalkylaminoisovaleric acids were distinctly more active than the corresponding mono-substituted ones. Of the 2 quaternary emetine derivatives tested, a correlation was evident between amebacidal activity and degree of quaternization of the 2 N atoms in the emetine molecule. Thus, N-benzoylemetine-N'' -ethoethylsulfate, with only one quaternized N, proved amebacidal at 500 ug./ml.; whereas N_methylemetine-N,N''_dimethiodide, with both Ns quaternized was only 10% as active. These exploratory tests suggest a few promising lines of further study, even though the compounds themselves displayed only a small fraction of emetine''s amebacidal activity in vitro (1 ug./ml.).