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Abstract  Formation of inclusion complexes between α- and β-cyclodextrins and three antipyrine type compounds (antipyrine, 4-amino-antipyrine, 4-nitroso-antipyrine), in solution and in solid state, has been investigated. UV–Vis measurements indicate that in solution antipyrine derivatives do not form inclusion complexes and oxidative process of amino group is not influenced by the presence of cyclodextrins. The oxidation of 4-amino-antipyrine to 4-nitroso-antipyrine using DPPH type radicals was investigated using spin trapping experiments in organic solvents and in water. These results were explained by betainic configuration of antipyrine derivatives in aqueous solutions. Formation of inclusion complexes in solid states was evidenced by DSC, as peaks associated with various thermodynamic events (dehydration, melting, thermal decomposition) are shifted towards higher temperature or disappear in case of inclusion complexes. [ABSTRACT FROM AUTHOR]

Abstract  The effect of Antipyrin upon the antioxidant activity of the riboflavin has been evidenced using chemiluminescent system luminol–hydrogen peroxide, in Tris–HCl buffer, pH 8.5. It was found that riboflavin antioxidant activity depends on the reaction time and the Antipyrin concentration. Using ESR spectroscopy the hydroxyl radical generation, in the mentioned chemiluminescent system, was evidenced. The interaction between reactants was also investigated by UV-VIS and fluorescence spectroscopy. The effect of Antipyrin concentration upon the riboflavin fluorescence has also been investigated. The fluorescence quenching by Antipyrin is not significant and subsequently the riboflavin fluorescence quenching doesn’t indicate an electron transfer process through diffusion-controlled mechanism. The results are discussed with relevance to the redox processes of riboflavin. [ABSTRACT FROM AUTHOR]

A new crown ether, derived from the 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH) and diaza-18-crown-6 (kryptofix 22) was synthesized. The physico-chemical properties of this new compound were studied using 1H- and 13C-NMR, EPR, UV-Vis, and IR spectroscopy. The compound has acid-base and redox properties, each of these involving a colour change (i.e., from yellow to red-brown for acid-base processes, and from yellow to violet for redox processes). The transport properties of the compound were studied by means of biphasic (l/l or s/l) systems. Thus, by an acid-base process alkaline cations were transported into an organic phase, as well as arginine; by a redox process, short-lived free radicals such as .C6H5 and .H were generated and observed by the EPR spin-trapping technique, using t-butyl-phenyl-nitrone (PBN) as spin-trap. [ABSTRACT FROM AUTHOR]

The action of different molar ratios of α, β, γ-cyclodextrin upon the chemiluminescence of the luminol-H2O2 in alkaline buffer Tris-HCl, pH=8.5 has been evidenced. It was found out that α, β, γ- cyclodextrin have an antioxidant capacity, probably due to the free radicals (that are generate in the system) encapsulation in the their cavity. This behaviour depends on α, β, γ-cyclodextrin molar ratio; α-cyclodextrin and γ-cyclodextrin protects more efficiently against free radicals than β-cyclodextrin. These findings could be very important regarding the oxidative stress process. [ABSTRACT FROM AUTHOR]