Abstract
The chain-breaking antioxidant activities of reduced form of novel type of geroprotectors, mitochondria-targeted quinones (QH(2)) have quantitatively been measured for the first time. To this end, the chain peroxidation of methyl linoleate (ML) in Triton micelles was used as a kinetic testing model. The studied QH(2) were lipophilic triphenylphosphonium cations conjugated by an aliphatic linker to an antioxidant, i.e. a ubiquinol moiety (MitoQH(2)) or plastoquinol moiety (SkQH(2)). The antioxidant activity was characterized by the rate constant k(1) for the reaction between QH(2) and the lipid peroxyl radical (LO(2) (.)) originated from ML: QH(2) + LO(2) (.) --> HQ(.) + LOOH. All the tested QH(2) displayed a pronounced antioxidant activity. The oxidized forms of the same compounds did not inhibit ML peroxidation. The value of k(1) for SkQH(2) far exceeded k(1) for MitoQH(2). For the biologically active geroprotectors SkQ1H(2), the k(1) value found to be as high as 2.2 x 10(5) M(-) (1)s(-) (1), whereas for MitoQH(2), it was 0.58 x 10(5) M(-) (1)s(-) (1). The kinetic behavior of QH(2) suggested that SkQ1H(2) can rather easily diffuse through lipid-water microheterogeneous systems.
Highlights
The oxidative stress caused by reactive oxygen species (ROS) is assumed to significantly contribute to aging and numerous age-related pathologies
The chain peroxidation of methyl linoleate (ML) in Triton micelles was used as a kinetic testing model
The non-inhibited oxidation of ML in Triton micelles is a chain process, which rate, R0, was found to be proportional to [ML] and square root of [azobis(2-amidinopropan) dihydrochloride (AAPH)] as it was reported in our preceding papers [21,22]
Summary
The oxidative stress caused by reactive oxygen species (ROS) is assumed to significantly contribute to aging and numerous age-related pathologies. Mitochondria are known as a place, where the most intensive ROS production can occur. No. targeting non-charged compounds to mitochondria was put forward [5, 6]. Murphy and coworkers initiated the practical realization of this idea [1, 7,8,9]. They synthesized and tested several mitochondria-targeted antioxidants conjugated to the lipophilic alkyltriphenylphosphonium cations. The ubiquinone moiety linked to triphenylphosphonium cation by C10 aliphatic chain, MitoQ (Figure 1), seemed to be the most promising [1, 4, 9]
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