Design, synthesis and biological evaluation of novel Pseudomonas aeruginosa DNA gyrase B inhibitors

In the present study, we attempted to develop a novel class of compounds active against Pseudomonas aeruginosa (Pa) by exploring the pharmaceutically well exploited enzyme targets. Since, lack of Pa gyrase B crystal structures, Thermus thermophilus gyrase B in complex with novobiocin (1KIJ) was used as template to generate model structure by performing homology modeling. Further the best model was validated and used for high-throughput virtual screening, docking and dynamics simulations using the in-house database for identification of Pa DNA gyrase B inhibitors. This study led to an identification of three lead molecules with IC₅₀ values in range of 6.25-15.6 µM against Pa gyrase supercoiling assay. Lead-1 optimization and expansion resulted in 15 compounds. Among the synthesized compounds six compounds were shown good enzyme inhibition than Lead-1 (IC₅₀ 6.25 µM). Compound 13 emerged as the most potential compound exhibiting inhibition of Pa gyrase supercoiling with an IC₅₀ of 2.2 µM; and in-vitro Pa activity with MIC of 8 µg/mL in presence of efflux pump inhibitor; hence could be further developed as novel inhibitor for Pa gyrase B.