Inhibition of heme synthesis by methyl-substituted benzimidazoles in vitro.

Emerson and associates (1) noted that 2,5-dimethylbenzimidazole appeared to act as a growth depressant when fed to rats in tests of compounds for vitamin Blz-like activity. This property was not exhibited by benzimidazole or any of the other monoor dimethylbenzimidazoles studied. They remarked that 2,5-dimethylbenzimidazole might have “inhibitor activity.” 2,5-Dimethylbenzimidazole inhibited red blood cell formation in mice made anemic by phenylhydrazine injection (2) and inhibited influenza virus multiplication (3). 5,6-Dimethylbenzimidazole had inhibitory properties for the vitamin Blz-requiring organisms Lactobacillus lactis Dorner, Lactobacillus leichmannii, and Euglena gracilis (4). Because of the chemical relationship of 2,5-dimethylbenzimidazole to the benzimidazole moiety of vitamin Blz and to the purines, we have investigated the effect of it and other methyl-substituted benzimidazoles on the synthesis of heme in vitro by chicken erythrocytes.