Study of inclusion complex of β-cyclodextrin and levofloxacin and its effect on the solution equilibria between gadolinium(III) ion and levofloxacin

Abstract

The formation of host–guest inclusion complex of levofloxacin with β-cyclodextrin (β-CD) was studied by fluorescence spectroscopy in buffer solution (pH 7.4) at 298 K. The experimental results confirmed the existence of 1:1 inclusion complex of levofloxacin with β-CD. The association constant of the β-CD inclusion complex was obtained from the Benesi–Hildebrand equation. The formation of the inclusion complex was confirmed by the IR and 1H NMR technique. The complex formation equilibria between Gd(III) ion and levofloxacin were investigated in aqueous solutions without and in the presence of β-cyclodextrin. The stoichiometry and stability constants of the formed complexes are reported, and the concentration distribution of the various complex species has been evaluated as a function of pH. The effect of β-cyclodextrin on dissociation constants, K a, of levofloxacin and stability constants of gadolinium(III)– levofloxacin complexes, β p,q,r, were examined. Furthermore, effect of levofloxacin on the speciation and distribution Gd(III) in human blood plasma was evaluated by computer simulation.