Synthesis and Antimicrobial Activity of 3-Alkylidene-2-Indolone Derivatives

The escalating threat of antibiotic-resistant bacteria and fungi underscores an urgent need for new antimicrobial agents. This study aimed to synthesize and evaluate the antimicrobial activities of two series of 3-alkylidene-2-indolone derivatives. We synthesized 32 target compounds, among which 25 exhibited moderate to high antibacterial or antifungal activities. Notably, compounds , , and demonstrated the highest antibacterial activity with a minimum inhibitory concentration (MIC) of 0.5 μg/mL, matching the activity of the positive control gatifloxacin against three Gram-positive bacterial strains: ATCC 6538, 4220, and Methicillin-resistant ATCC 43300. Moreover, the three most active compounds , , and were evaluated for their in vitro cytotoxicity in the HepG2 cancer cell line and L-02; only compound was found to exert some level of cytotoxicity. These findings suggest that the synthesized 3-alkylidene-2-indolone derivatives hold potential for further development as antibacterial agents.