Novel benzimidazole derived naphthalimide triazoles: synthesis, antimicrobial activity and interactions with calf thymus DNA

A novel series of benzimidazole derived naphthalimide triazoles and some corresponding triazoliums have been successfully synthesized and characterized by H-1 NMR, C-13 NMR, H-1-H-1 COSY, IR and HRMS spectra. All the new compounds were screened for their antimicrobial activities in vitro by two-fold serial dilution. 2-Chlorobenzyl triazolium 8g and compound 9b with octyl group exhibited the best antibacterial activities among all the tested compounds, especially against S. aureus with inhibitory concentration of 2 mu g/mL which was equipotent potency to Norfloxacin (MIC=2 mu g/mL) and more active than Chloromycin (MIC=7 mu g/mL). Triazoliums 8g and 8f bearing 3-fluorobenzyl moiety displayed the best antifungal activities (MIC=2-19 mu g/mL) against all the tested fungal strains without being toxic to PC12 cell line within concentration of 128 mu g/mL. Further investigations by fluorescence and UV-Vis spectroscopic methods revealed that the compound 8g could effectively intercalate into calf thymus DNA to form the 8g-DNA complex which could block DNA replication, exerting powerful antimicrobial activities.