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The formation of host-guest inclusion complex of levofloxacin with b-cyclodextrin (b-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 b-CD. The association constant of the b-CD inclusion complex was obtained from the Benesi-Hildebrand equation. The formation of the inclusion complex was confirmed by the IR and 1 H NMR technique. The complex formation equilibria between Gd(III) ion and levofloxacin were investigated in aqueous solutions without and in the presence of b-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 b-cyclodextrin on dissociation constants, K a , of levofloxacin and stability constants of gadolinium(III)-levofloxacin complexes, b 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. Graphical abstract

Nine 1,2,4-triazole-3-thiones containing phenolic acid moiety have been synthesized and examined by scavenging of stable DPPH (2,2-diphenyl-1-picrylhydrazyl) radical, measurement of reducing capacity, cyclic voltammetry experiments and density functional theory (DFT). The differences in DPPH-radical scavenging activity of the compounds 4 a-i are affected by the sta-bility of the corresponding radicals or radical cations and possibility of delocalization of unpaired electron through benzene and triazole ring. Significantly, lower proton affinity (PA) values than bond dissociation enthalpy (BDE) indicate SPLET (sequential proton loss electron transfer) mechanism under these experimental conditions.[a] N. Ivanović, Dr.