Synthesis and antimicrobial activity of quaternary N-aryl-5,6-benzoquinaldinium derivatives

A series of quaternary N-aryl-5,6-benzoquinaldinium derivatives have been synthesized. Their antimicrobial activity (E. coli, S. aureus) has been tested. It was found that introduction of a new annelated benzene ring into the heterocyclic molecule (compared with quinolinium and benzoquinolinium compounds) leads to a significant increase of the antibacterial activity. Electron-withdrawing substituents in the quaternary phenyl group decrease slightly the antimicrobial effect. Since better results have been obtained for N-phenyl-5,6-benzoquinaldinium tetrafluoroborate, biological investigations were continued on the additional test cultures S. saprophyticus, Salmonella spp., Micrococcus luteus, Proteus vulgaris, Bacillus subtilis, and Candida albicans. The observation of high fungicidal activity against C. albicans was promising.