A MOLECULAR ELECTROSTATIC POTENTIAL MAPPING STUDY OF SOME FLUOROQUINOLONE ANTIBACTERIAL AGENTS

Molecular electrostatic potential (MEP) maps of some fluoroquinolones having varying degrees of activity against the bacterium Staphylococcu s Aureus have been studied using the optimized hybridization displacem ent charges (HDC) combined with Lowdin charges obtained by the AM1 met hod. The roles of different substitutions at the N-1-position in the p arent quinolone ring have been studied. The conformation of the carbox ylic group attached to the quinolone ring was shown to be such that th ere is an intramolecular hydrogen bonding between the hydrogen atom of this group and the oxygen atom of the carbonyl group of the quinolone moiety. The carbonyl oxygen atom of the quinolone moiety, hydroxyl ox ygen atom of the carboxylic group and the terminal nitrogen atom of th e piperazin ring attached to the quinolone ring appear to be involved in the action of the drugs through electrostatic interactions while th e N-1-alkyl substituents seem to be involved in the same through hydro phobic interactions.