Design, Synthesis, Biological Evaluation, and Molecular Docking Studies of Pleuromutilin Derivatives Containing Thiazole

In this study, we designed and synthesized a series of pleuromutilin derivatives containing thiazole. The in vitro antimicrobial efficacy of these synthesized compounds was examined by using four strains. Compared with tiamulin (MIC = 0.25 mu g/mL), compound 14 exhibited potency in inhibiting MRSA growth (MIC = 0.0625 mu g/mL) in these derivatives. Meanwhile, the time-killing kinetics further demonstrated that compound 14 could efficiently inhibit the MRSA growth. After exposure at 4 x MIC, the postantibiotic effect (PAE) of compound 14 was 1.29 h. Additionally, in thigh-infected mice, compound 14 exhibited a more potent antibacterial efficacy (-1.78 +/- 0.28 log(10) CFU/g) in reducing MRSA load compared to tiamulin (-1.21 +/- 0.23 log(10) CFU/g). Moreover, the MTT assay on RAW 264.7 cells demonstrated that compound 14 (8 mu g/mL) had no significant cytotoxicity. Docking studies indicated the strong affinity of compound 14 toward the 50S ribosomal subunit, with a binding free energy of -9.63 kcal/mol. Taken together, it could be deduced that compound 14 was a promising candidate for treating MRSA infections.