Synthesis and Antimicrobial Evaluation of (Z)-5-((3-phenyl-1H-pyrazol-4- yl)methylene)-2-thioxothiazolidin-4-one Derivatives.

BACKGROUND: An alarming increment in pathogenic resistance to existing anti-microbial agents is a serious problem and the treatment of these bacterial infections is becoming increasingly challenging. Therefore, there is an urgent need to develop novel antimicrobial agents.

OBJECTIVE: As a part of our ongoing studies toward the development of novel antibacterial agents, the synthesis and antibacterial activity of a series of (Z)-5-((3-phenyl-1H-pyrazol-4-yl)methylene)-2-thioxothiazolidin-4-one derivatives will be discussed in this study.

METHOD: (Z)-5-((3-phenyl-1H-pyrazol-4-yl)methylene)-2-thioxothiazolidin-4-one derivatives were designed, synthesized and evaluated for antibacterial activity. The structures were confirmed by IR, 1H NMR, 13C NMR and mass spectrometry. All of the synthesized compounds were evaluated in vitro using a 96-well microtiter plate and a serial dilution method to obtain their minimum inhibitory concentration (MIC) values against a variety of different strains, including multidrug-resistant clinical isolates.

RESULTS: The antibacterial test in-vitro showed that most compounds in series 7 and 9 exhibited significant inhibitory activities against anaerobic bacteria (Streptococcus mutans) strains with a MIC value of 1 µg/mL. Compounds 7c and 9c showed the most potent activity against MRSA (3167 and 3506) with a minimum inhibitory concentration (MIC) value of 1 µg/mL, which is equivalent to moxifloxacin and greater than gatifloxacin, oxacillin and norfloxacin. Additionally, compound 9c showed potent antibacterial activity against Bacillus subtilis (aerobic bacteria) with a MIC value of 2 µg/mL.

CONCLUSION: The work suggests that these type of rhodanine compounds had a better potent activity against MRSA compared with other perviously reported rhodanine derivatives, which might provide a valuable information for the development of new antibacterial agents against multidrug-resistant clinical isolates MRSA.