A study on the interactions between coenzyme Q(0) and superoxide anion. Could ubiquinones mimic superoxide dismutase (sod)?

An electrochemical study was carried out on 1,4-benzoquinone, duroquinone, coenzymes Q(0) and Q(10) in the absence and in the presence of molecular ox ygen in aprotic (DMF) and protic (DMF/H2O 95:5 (v/v)) media. Water was adde d because the investigated reactions are deeply influenced by the presence of protons. Q(0) and Q(10) exhibited a similar electrochemical behaviour. S ince Q(0) is more soluble in protic medium than the biologically more impor tant analogue Q(10), it was chosen as a model for a more detailed investiga tion. Voltammetric studies of Q(0) carried out in aprotic and protic media in the presence of oxygen showed that, besides simple O-2(.-) dismutation, theQ(0) promoted dismutation of O-2(.-) should also be considered. Spectroe lectrochemical experiments with the same experimental conditions support th e electrochemical results, showing that in the presence of superoxide and i n aprotic medium semiquinone Q(0) gives rise to a disproportionation equili brium, while in the presence of water it tends to be reoxidized to the star ting eo by OOH.. EPR measurements are also in agreement with these results.