Coenzyme Q10 in human blood: Native levels and determinants of oxidation during processing and storage

Adrian A. Franke, Cynthia M. Morrison, Jesse L. Bakke, Laurie J. Custer, Xingnan Li, Robert V. Cooney

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Coenzyme Q10 (Q10) is present in the circulation mainly in its reduced form (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 an RP-(U)HPLC method with coulometric detection to measure natively circulating UL10 and UN10 concentrations by adding a ubiquinol/ubiquinone mixture as an internal standard 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 because the internal standards exactly paralleled the chemical behavior of Q10. This technique applied to blood (n = 13) revealed Q10 levels of 680-3300nM with a mean UL10:UN10 ratio of 95:5, 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°C, its oxidation was catalyzed dose dependently by α-tocopherol and butylated hydroxytoluene, particularly when present in combination. Key structural features for the catalytic pro-oxidant properties of phenolic antioxidants included two substituents vicinal to the phenolic hydroxyl group.

Original languageEnglish
Pages (from-to)1610-1617
Number of pages8
JournalFree Radical Biology and Medicine
Issue number12
StatePublished - Jun 2010


  • Coenzyme Q10
  • Free radicals
  • HPLC
  • Internal standard
  • Native blood levels
  • Redox status
  • Ubiquinol
  • Ubiquinone


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