Abstract:
After a while, following the advantages provided by the discovery of antibiotics, attention quickly turned to drug resistance due to the development of antibacterial resistance in bacteria. This breakthrough of resistance led to exploring new ways of treating infectious diseases like the invention of new compounds including Schiff bases with their metal complexes that can create a new class of antimicrobial drugs with exciting potential. In this study, the antibacterial activity of fluorinated 3,5'- di-tert butylsalicylaldehyde Schiff base ligands with their palladium and copper complexes (6 compounds) were tested against Klebsiella pneumoniae, Proteus mirabilis, and Streptococcus pyogenes. The MTT method was used to determine the MIC₅₀ values of gentamicin and each tested compound. The compounds and the antibiotic were prepared in four concentrations: 1 μM, 10 μM, 100 μM, and 1000 μM, and were added to 96-well culture plates with 100 μL of bacterial suspension (0.5 McFarland) followed by MTT application and reading plates by by ELIZA plate reader at 570 nm. The results showed an MIC50 value of 1.91 μM for gentamicin against K. pneumoniae, 1.92 μM, and 2.09 μM against P. mirabilis and S. pyogenes, respectively. The MIC50 values of Schiff base compounds ranged between 10.82 to 25.44 μM for K. pneumoniae, 5.28 to 11.12 μM for P. mirabilis, and 3.11 to 5.10 μM for S. pyogenes. The most effective compound for both P. mirabilis and S. pyogenes was (Bis(2,4,6-trifluorophenyl-3,5-di-tert- butylsalicilaldiminato) Cu(II)) with an MIC50 value of 5.28 μM and 3.11 μM, respectively. While for K. pneumonia it was (3,4,5-trifluorophenyl-3,5-di-tert butylsalicilaldiminato) with an MIC50 value of 10.82 μM. The fluorinated Schiff bases showed moderate to good antibacterial activities. The effectiveness of the copper complexes of the compounds on both gram-negative and gram-positive bacteria was more significant than their corresponding ligands.
