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Native levels and determinants for oxidation of coenzyme Q10 in human plasma
Author(s) -
Franke Adrian A,
Morrison Cynthia M,
Bakke Jesse L,
Custer Laurie J,
Li Xingnan,
Cooney Robert V
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.321.3
Subject(s) - coenzyme q10 , ubiquinol , chemistry , chromatography , antioxidant , redox , high performance liquid chromatography , toluene , organic chemistry , coenzyme q – cytochrome c reductase , biochemistry , cytochrome c , mitochondrion
Coenzyme Q10 (Q10) is present in the circulation mainly reduced (ubiquinol‐10; UL10), but oxidizes quickly ex vivo to ubiquinone‐10 (UN10). Therefore, native UL10/UN10 ratios, used as markers of redox status and disease risk, are difficult to measure. We established a RP‐(U)HPLC method with coulometric detection to measure natively circulating UL10 and UN10 concentrations by adding a ubiquinol/ubiquinone mixture as internal standards immediately after plasma preparation. This allowed adjustment for unavoidable artificial UL10 oxidation as well as for total losses (or gains) of analytes during sample storage, processing, and analysis since the internal standards exactly paralleled the chemical behavior of Q10. This technique applied to blood collected from 13 healthy volunteers revealed Q10 levels of 680–3300 nM with a UL10/UN10 ratio of 95:5 (mean) which was inversely associated with total Q10 (r=−0.69; p=0.004). The oxidation of UL10 to UN10 was equimolar, increased by O2, and decreased by lower temperatures or various degassing methods. Although UL10 was stable in blood or when pure in organic solvents at 22 oC, its oxidation was catalyzed dose dependently by alpha‐tocopherol and butylated hydroxy toluene, particularly when present in combination. Key structural features for the catalytic pro‐oxidant properties of phenolic antioxidants included two aliphatic substituents vicinal to the phenolic hydroxyl group.