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

Bis-nitroxide malonate methanofullerene (NO center dot)(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-(beta-oxyethyl)-4,6-dimethyl-1,2-dihydro-2-oxopyrimidine (xymedon (R)). (NO center dot)(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 center dot)(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 center dot)(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 (R) with (NO center dot)(2)-MF monolayers was confirmed by the increasing of limiting area A(0) from 0.88 nm(2) up to 1.70 nm(2) of (NO)2 center dot-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 (R) in the presence of additives (0.001%) of (NO center dot)(2)-MF in the experiments on the rats. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).