Nitroxydes 105: cinetique de reduction d'un radical nitroxyde par l'acide ascorbique en presence de β-cyclodextrine

Cyclodextrin Inclusion Complexes

“…Various stable nitroxide radicals ( 2,100,106,284,311,328,329,(333)(334)(335), and y irradia tion genera ted radicals from incorporated gues ts ( 4-,5,7 ], have been studied in great number by electron spin resonance spectroscopy. The 'H-NMR spectra of stable nitroxide radical spin labels showed enhanced relaxation of the carbohydrate proton nuclei in the vicinity of the binding site ( 330 1.…”

Nitroxide Radicals: Properties, Synthesis and Applications

“…179 reported the partial protection of TEMPO to ascorbate reduction by adding β-cyclodextrin in the media. This approach has been successfully expanded to the spin trapping technique 180 and recently a [1]rotaxane based on a TEMPO unit linked to a β-cyclodextrin moiety has been synthesized and exhibited significant resistance to glutathione (GSH) reduction (Scheme 5.36).…”

Radical intermediates and antioxidant activity of ascorbic acid

“…19 20 21 22 There have been a number of kinetic studies on the reduction of nitroxides by ascorbic acid carried out in aqueous solution [64][65][66][67], in micelles [64], in natural biomembranes [7,60] and in fl-cyclodextrin [68][69][70]. The common feature of these studies involves the determination of the pseudo-first order rate constants for the decay of the nitroxides by ESR in the presence of a large excess of ascorbic acid.…”

“…Ingold and Rassat and their coworkers [68,69] have studied the reduction of nitroxide by ascorbic acid in cyclodextrin and, by determining the dependence of pseudo-first order rate constants upon the concentration of ascorbic acid, evaluated the second order rate constants for the reaction. The mechanism they have proposed is depicted as follows (Eqs.…”

“…Ingold et al [68,69] and others [70] have studied the reduction of nitroxides 19(X=H), 21(X=O=), 21(X=OH), and 22 by ascorbic acid in the presence of fl-cyclodextrin. They both found that the reaction rate is slightly decreased in fl-cyclodextrin compared to that in water with the exception of 21(X=O=).…”