Nitroxide malonate methanofullerene as biomimetic model of interaction of nitroxide species with antioxidants.

Abstract Bis-nitroxide malonate methanofullerene (NO ) 2 -MF was studied as a biomimetic model of reduction–oxidation activity with natural compounds—cytochrome c (cyt c ), dihydroquercetin (DHQ), ascorbic acid (AA) and synthetic drug—1-(β-oxyethyl)-4,6-dimethyl-1,2-dihydro-2-oxopyrimidine (xymedon ® ). (NO ) 2 -MF may be used as the component of Langmuir monolayers on an aqueous subphase and as the adsorbate on silica gel. The activity of (NO ) 2 -MF in the reaction with cyt c was compared with the effect of nitroxide species such as gaseous nitric oxide, 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) by using UV–vis and EPR-spectra. It has been shown, that iron(III) in cyt c 3+ under action (NO ) 2 -MF was reduced up to iron(II), similar effect was observed under the influence of gaseous NO in aqueous solution, but reduction of iron(III) in heme cyt c was reversible in the presence of TEMPO. Therefore, the state of Fe-heme in cyt c can be used as the indicator of the interaction of cyt c with nitroxide species in vitro . The interaction of cyt c , DHQ, xymedon ® with (NO ) 2 -MF monolayers was confirmed by the increasing of limiting area А 0 from 0.88 nm 2 up to 1.70 nm 2 of (NO ) 2 -MF on the aqueous subphase, by the paramagnetism and UV–vis spectral data changes. These results can be explained by appearance of oxoammonium ion (NO + ) 2 -MF adlayers and monolayers. The antioxidant and regenerating effects were shown when treating wounds by xymedon ® in the presence of additives (0.001%) of (NO ) 2 -MF in the experiments on the rats.