Synthesis and bactericidal evaluation of fluoroquinolone derivatives

Fluoroquinolone resistance has been constantly reported worldwide. Therefore, several approaches are explored in the search for new antimicrobials. In this work, a series of N-acyl-hydrazonic and thioureidic fluoroquinolone derivatives were synthesized and evaluated for antibacterial activity (Figure 1).

The in vitro antimicrobial activity of all the synthesized compounds were tested against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC-33591, Klebsiella pneumoniae ATCC-700603, Pseudomonas aeruginosa ATCC-28753, Shigella sonnei ATCC-25931, Salmonella enterica ATCC-10749. All of the title compounds have considerable activity against the strains, and exhibit exceptional potency in inhibiting the growth of Escherichia coli and Shigella sonnei (minimum inhibitory concentration: 0.015–4 μg/mL). Hydrazone derivatives 5ae and 5af presented comparable activity with ciprofloxacin against S.aureus and E. coli. The most active compound was thiourea 7ab, 4-fold more potent than ciprofloxacin against Shigella sonnei and 2-fold more potent against S.aureus. The results demonstrated the potential of developing new quinolone derivatives against bacterial infections.