Based on the mechanism of action, several groups of antimicrobial agents are distinguished – one consists of compounds that act on different cellular processes of DNA modification. This also includes new inhibitors of the bacterial DNA gyrase subunit A called NBTI (novel bacterial topoisomerase inhibitors). Type II topoisomerases, including DNA gyrase, are enzymes that cleave both strands of DNA and thus allow the introduction of supercoils or release of topological tension, which is important for the storage of genetic material, and processes of transcription, recombination and replication. NBTIs achieve their antibacterial effect by inhibiting exactly this enzyme. NBTIs consist of a left-hand side that forms interactions with DNA, a right-hand side that binds to hydrophobic pocket of DNA gyrase and a linker that connects the two parts and is responsible for their proper orientation.
In the experimental part of this master's thesis we first searched for new potential NBTIs through virtual screening and molecular docking. Molecular structures with the preserved 1,5-naphthyridine left hand side and the 4-amino-1-ethylpiperidine linker were designed and subsequently synthesized. For the right-hand side of the molecule various mono- and disubstituted aromatic bicyclic fragments were used in the first series and monocyclic ones in the second series. Prepared compounds were characterized using liquid chromatography, various spectroscopic techniques and by measuring of their melting point. This was followed by evaluation of the inhibitory effect of potential NBTIs by determining the half maximal inhibitory concentration IC50 on isolated DNA gyrase Staphylococcus aureus and Escherichia coli and the minimum inhibitory concentration MIC on both aforementioned bacteria and many other bacterial strains.
The results confirmed and re-outlined the effect of the known difference in the space size at the active site of DNA gyrase in S. aureus and E. coli on the spectrum of NBTI activity and expanded set of potential antibacterial compounds with some promising fluorosubstituted molecules that allow insight into possibility of fluoro-DNA gyrase interaction formation.
|
