Antioxidant Potential of Aqueous Dispersions of Fullerenes C, C, and Gd@C.

The antioxidant potential (capacity and activity) of aqueous fullerene dispersions (AFD) of non-functionalized C, C, and Gd@C endofullerene (in micromolar concentration range) was estimated based on chemiluminescence measurements of the model of luminol and generation of organic radicals by 2,2'-azobis(2-amidinopropane) dihydrochloride (ABAP). The antioxidant capacity was estimated by the TRAP method, from the concentration of half-suppression, and from the suppression area in the initial period. All three approaches agree and show that the antioxidant capacity of AFDs increased in the order Gd@C < C < C. Mathematical modeling of the long-term kinetics data was used for antioxidant activity estimation. The effect of C and C is found to be quenching of the excited product of luminol with ABAP-generated radical and not an actual antioxidant effect; quenching constants differ insignificantly. Apart from quenching with a similar constant, the AFD of Gd@C exhibits actual antioxidant action. The antioxidant activity in Gd@C is 300-fold higher than quenching constants.