Design, green synthesis, and quorum sensing quenching potential of novel 2-oxo-pyridines containing a thiophene/furan scaffold and targeting a LasR gene on P. aeruginosa

Abstract

The current trend in fighting bacteria is attacking the virulence and quorum-sensing (QS) signals that control bacterial communication and virulence factors, especially biofilm formation. This study reports new Schiff bases and tetracyclic rings based on a pyridine pharmacophore by two methods: a green approach using CAN and a conventional method. The structure of designed derivatives was confirmed using different spectroscopies (IR and ¹H/¹³C NMR) and elemental analysis. The designed derivatives exhibited good to moderate inhibition zones against bacterial and fungal pathogens. In addition, six compounds 2a,b, 3a,b, and 6a,b displayed potency against tested pathogens with eligible MIC and MBC values compared to standard antimicrobial agents. Compound 2a displayed MIC values of 15.6 μg mL⁻¹ compared to Gentamicin (MIC = 250 μg mL⁻¹ against K. pneumoniae), while compound 6b exhibited super-potent activity against P. aeruginosa, and K. pneumoniae with MIC values of 62.5 and 125 μg mL⁻¹, as well as MBC values of 31.25 and 15.6 μg mL⁻¹ compared to Gentamicin (MIC = 250 and 125 μg mL⁻¹ and MBC = 62.5 μg mL⁻¹), respectively. Surprisingly, these six derivatives revealed bactericidal and fungicidal potency and remarkable anti-biofilm activity that could significantly reduce the biofilm formation against MRSA, E. coli, P. aeruginosa, and C. albicans. Furthermore, the most active derivatives reduced the LasR gene's production between 10–40% at 1/8 MICs compared with untreated P. aeruginosa. Besides, they demonstrated promising safety profile on Vero cells (normal cell lines) with IC₅₀ values ranging between (175.17 ± 3.49 to 344.27 ± 3.81 μg mL⁻¹). In addition, the in silico ADMET prediction was carried out and the results revealed that these compounds could be used with oral bioavailability with low toxicity prediction when administered as a candidate drug. Finally, the molecular docking simulation was performed inside LasR and predicted the key binding interactions responsible for the activity that corroborated the biological results.