Bismuth-norfloxacin complex: synthesis, physicochemical and antimicrobial evaluation

Norfloxacin is a fluoroquinolone antibacterial agent which is active against various Gram-positive as well as Gram-negative microorganisms. Presence of metal ions considerably alters the activity of fluoroquinolones against potentially susceptible bacteria. As bismuth is known to possess a good antibacterial activity, bismuth complex of norfloxacin was prepared by reacting bismuth citrate with aqueous solution of norfloxacin. The structure of the bismuth-norfloxacin complex (BNC) was confirmed by spectral, chemical and elemental analysis. Antimicrobial studies were carried out using agar diffusion method against Escherichia coli (ATCC 25922), Klebsiella pneumoniae (NTCC 10320), Staphylococcus aureus (ATCC 29213), Bacillus pumilis (NTCC 8241) and Staphylococcus epidermidis (ATCC 12228). The results showed significant increase (p<0.05, Tukeys test) in antibacterial activity of BNC as compared with norfloxacin and physical mixture of norfloxacin and bismuth citrate. This increase in activity is being considered due to increased bioavailability of the metal drug complex. Thus, the use of the BNC may be preferable over norfloxacin alone.