Design and synthesis of new norfloxacin-1,3,4-oxadiazole hybrids as antibacterial agents against methicillin-resistant Staphylococcus aureus (MRSA)

Toward the search of new antibacterial agents to control methicillin-resistant Staphylococcus aureus (MRSA), a class of new norfloxacin-1,3,4-oxadiazole hybrids were designed and synthesized. Antibacterial activities against drug-sensitive bacteria S. aureus and clinical drug resistant isolates of MRSA were evaluated. Compound 5k exhibited excellent antibacterial activities against S. aureus (MIC: 2 μg/mL) and MRSA1–3 (MIC: 0.25–1 μg/mL). The time-kill kinetics demonstrated that compound 5k had an advantage over commonly used antibiotics vancomycin in killing S. aureus and MRSA. Moreover, compound 5k could inhibit the bacteria and destroy their membranes in a short time, and showed very low cytotoxicity to NRK-52E cells. Some interesting structure-activity relationships (SARs) were also discussed. These results indicated that these norfloxacin-1,3,4-oxadiazole hybrids could be further developed into new antibacterial agents against MRSA.