Substituted 4,7-dihydroxyindoles and related quinonoid derivatives as potential antimicrobial agents

The antimicrobial activity of some 4,7-dihydroxyindole derivatives and indole-4,7-quinones was examined by determining the MIC against selected typical microorganisms (bacteria and fungi). A few of the compounds examined showed only a feeble inhibitory effect against some Gram-positive strains. Activity seems to be correlated with the lipophilic character of the molecules; in fact, all compounds containing a strong hydrophilic group, like a carboxyl, proved completely inactive.