Protonation Equilibria and Lipophilicity of Sarafloxacin

The main objective of this work was to quantify the lipophilicity of sarafloxacin in the form of the apparent and true partition coefficient in an n-octanol/buffer system. For that purpose the ionization constants were determined by a spectrophotometric method, and the distribution profiles of microspecies in water as a function of pH for this fluoroquinolone were established. The maximum concentration of the neutral species occurs at the sarafloxacin isoelectric point, pH = 5.5. The apparent partition coefficient in the n-octanol/buffer system versus the pH profile of sarafloxacin displayed a parabolic behavior that reached a maximum near the pH of the isoelectric point. The true partition coefficient was calculated from the log P-app and microconstant values and has the value of 0.846 +/- 0.021.