3-Naphthylindoles as new promising candidate antioxidant, antibacterial, and antibiofilm agents

摘要

Indole derivatives have attracted significant attention in organic synthesis and bioactivity research owing to their substantial biological activity. In the present study, several 3-naphthylindole analogues were synthesized by direct arylation of 1-diazonaphthalene-2-(1H)-ones by rhodium(II)-catalyzed cross-coupling reaction and their antioxidant and antibacterial properties evaluated. Among the analogues tested, compound 3m displayed the highest antioxidant activity [as evaluated by ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) tests], whereas compound 3c exhibited the lowest activity. The compounds were also screened against biofilm-forming bacterial species (Gram-negative Escherichia coli and Pseudomonas aeruginosa as well as Gram-positive Staphylococcus aureus and Bacillus cereus). Compounds 3b, i, j, p displayed potent antibacterial activity against E. coli. Similarly, compound 3p exhibited activity superior to quercetin (4.2 mu g/mL) by completely inhibiting biofilm formation by E. coli. Moreover, the half-maximal inhibitory concentration (IC50) values of compounds 3e, j against B. cereus were comparable to that of standard quercetin.