Abstract: The invention relate to a method for detecting cytochrome c in a given biological sample, comprising: adding to said sample an efficient amount of two redox couples allowing for a cycling oxido-reduction of cytochrome c, said couples comprising an oxidizing agent consisting of cytochrome c oxidase enzyme and a reducing agent specific for cytochrome c with a reduced co-factor; measuring, by a biophysical system depending on the co-factor and allowing to distinguish the co-factor oxidized form from the reduced form, the oxidation of the co-factor which is oxidized during said cycling redox reaction; the amount of the co-factor oxidized form being correlated to the concentration of cytochrome c in the sample.

Abstract: A method of treating or preventing a disorder resulting from a mitochondr dysfunction induced by an iron overload including Friedreich Ataxia, hypertrophic cardiomyopathy, Hallervorden-Spatz disease, sideroblastic anemia by administering an effective amount of an ubiquinone derivative such as idebenone, decylubiquiqnone, coenzyme Q2, coenzyme Q4, and coenzyme Q6, either alone or in conjunction with a second therapeutic agent or a non-reducing antioxidant.