Scheme 1.
Synthesis of bis(thiazol-5-yl)p-tolyl detivatives (10–23)a and (24-31b).
Table 1.
The effect of various substitutions incorporated in bis(thiazol-5-yl)p-tolyl derivatives (10–23)a and (24-31b) on the obtained synthesized yealds.
Fig 1.
In vitro antimicrobial activity of bis(thiazol-5-yl)phenylmethane derivatives 10–31 and control antimicrobial compounds at a concentration of 100 μM against selected multidrug-resistant bacterial strains.
Bacterial strains were exposed to compounds and control antimicrobial drugs at a fixed concentration of 100 μM for 18 hours. Subsequently, resazurin (25 μM) was added, and the plates were further incubated for 3 hours. Following incubation, the optical density at 700 nm (OD700 nm) was measured, and the post-treatment viability percentage was normalized to the untreated control (UC). AZT-aztreonam, COL-colistin, FOX-cefoxitin, MEM-meropenem, OX-oxacillin, VAN-vancomycin. The data presented in the figure represents the mean ± standard deviation (SD) from three independent experimental replicates.
Table 2.
In vitro minimal inhibitory concentration (MIC) values (μg/mL) of compounds 10–31 against drug-resistant Gram-positive bacterial strains.
Table 3.
In vitro MIC values (μg/mL) of compounds 10–31 against Staphylococcus aureus with genetically defined resistance mechanisms.
Table 4.
The effect of serum addition of the MIC values (μg/mL) for compounds 23a and 28b.
Fig 2.
Bis(thiazol-5-yl)phenylmethane derivatives 23a and 28b exhibit a anti-biofilm activity against S. aureus with genetically defined resistance mechanisms.
Bacterial biofilms were grown for 24 hours in static conditions and then biofilms were exposed with compounds 23a, 28b or vancomycin (VAN) in fresh media for 18 hours. Biofilm mass was measured by using crystal violet assay. Panel A shows representative images of crystal violet assay. Panel B demonstrates the spectrophotometric measurements of compound-exposed biofilms. The data presented in the figure represents the mean ± standard deviation (SD) from three independent experimental replicates.
Table 5.
Predicted binding free energy values (ΔGbin, kcal/mol) for the docking of compounds with Mur family proteins in S. aureus.
Fig 3.
Compound 23a interacts with S. aureus MurC ligase.
Panel A demonstrates the potential binding site of 23a into MurC. Panel B shows plotted 2D maps of H-bonds and hydrophobic interactions of 23a with MurC residues. Van der Waals, Pi–Cation, Pi–Pi stacked, Pi–Pi T-shaped, amide-Pi stacked, alkyl and Pi–alkyl are considered hydrophobic interactions.
Fig 4.
Compound 28b interacts with S. aureus MurC ligase.
Panel A shows potential binding site of 28b into MurC. Panel B demonstrates plotted 2D maps of H-bonds and hydrophobic interactions of 28b with MurC residues. Van der Waals, Pi–Pi stacked, Pi–Pi T-shaped and Pi–alkyl is considered hydrophobic interactions.
Fig 5.
Compounds 23a and 28b shares overlapping positions with UDP-N-acetyl-alpha-D-muramate binding pocket in S. aureus MurC.
Panel A shows the docking poses for UDP-N-acetyl-alpha-D-muramate (green), 23a (blue), and 28b (yellow) into MurC. Panel B demonstrates 2D maps of H-bonds and hydrophobic interactions of UDP-N-acetyl-alpha-D-muramate with MurC amno acid residues. Van der Waals, Pi–cation, Pi–donor hydrogen bond, alkyl and Pi–alkyl are considered hydrophobic interactions.
Table 6.
Binding site contacts of compound 23a, 28b, and substrate into MurC.
Fig 6.
The bis(thiazol-5-yl)phenylmethane derivatives 10–31 exhibit favorable A549 and THP-1 derived macrophage cytotoxicity profiles.
The data represents the mean ± standard deviation (SD) from three independent experimental replicates.
Fig 7.
Hemolytic activity assessment of compounds 23a and 28b using rabbit erythrocyte hemolysis assay.
Rabbit erythrocytes were exposed to compounds 23a and 28b at a concentration of 100 μM for a duration of 1 hour at 37°C. Hemolytic activity was evaluated, and results were compared to the vehicle control (DMSO). The results expressed as mean values ± standard deviation (SD) are derived from three independent experimental replicates.