Antimicrobial Activity of Tryptanthrins in Escherichia coli

Tryptanthrins have potential therapeutic activity against a wide variety of pathogenic organisms, although little is known about their mechanism. Activity against Escherichia coli, however, has not been examined. The effects of tryptanthrin (indolo[2,1-b]quinazolin-6,12-dione) and nine derivatives on growth, survival, and mutagenesis in E. coli were examined. Analogues with a nitrogen atom at the 4-position of tryptanthrin stopped log phase growth of E. coli cultures at concentrations as low as 5 μM. Tryptanthrins decreased viability during incubation with cells in buffer by factors of 10−2 to