1H NMR and electron paramagnetic resonance (EPR) titrations were used to determine the association constants of the complexes of α-phenyl-N-tert-butylnitrone (PBN) analogues and their Superoxide spin adducts, respectively, with methylated-β-cyclodextrins. A 1:1 stoichiometry for the nitrones with randomly methylated β-cyclodextrin and 2,6-di-O-methyl-β-cyclodextrin and 1:1 and 1:2 stoichiometries for the corresponding cyclodextrin-nitroxide complexes were observed. After the Superoxide radical spin trapping reaction, EPR titrations afforded the association constants of the corresponding cyclodextrin-nitroxide complexes. Two-dimensional EPR simulations indicated a bimodal inclusion of the nitroxide free radical spin adducts into the cyclodextrins. For all the nitrone-cyclodextrin and nitroxide-cyclodextrin complexes, the association constants were always higher for the nitroxide complexes than for the nitrone complexes. A cooperative system concerning the complexation of the nitroxide spin adduct with a cyclodextrin was evidenced by EPR titrations. The efficiency of the cyclodextrin inclusion technique to trap Superoxide and to resist bioreduction by sodium L-ascorbate was also investigated.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry