title: Rapid and sensitive analysis of reduced and oxidized coenzyme Q10 in human plasma by ultra performance liquid chromatography-tandem mass spectrometry and application to studies in healthy human subjects.
abstract: BACKGROUND
  Coenzyme Q10 is an endogenous antioxidant as well as a popular dietary supplement. In blood circulation, coenzyme Q10 exists predominantly as its reduced ubiquinol-10 form, which readily oxidizes to ubiquinone-10 ex vivo. Plasma concentrations of coenzyme Q10 reflect net overall metabolic demand, and the ratio of ubiquinol-10:ubiquinone-10 has been established as an important biomarker for oxidative stress. However, the lability of ubiquinol-10 makes accurate determination of both forms of coenzyme Q10 difficult. Ex vivo oxidation of ubiquinol-10 to ubiquinone-10 during sample collection, processing and analysis may obfuscate the in vivo ratio.
  
  
  METHODS
  We developed a rapid and sensitive method for the determination of ubiquinol-10 and ubiquinone-10 in human plasma, using coenzyme Q9 analogues as internal standards. Single-step protein precipitation in 1-propanol, a lipophilic and water-soluble alcohol, allowed for rapid extraction.
  
  
  RESULTS
  Analysis by ultra performance liquid chromatography-tandem mass spectrometry provided rapid run-time and high sensitivity, with lower limits of quantitation for ubiquinol-10 and ubiquinone-10 of 5 μg/L and 10 μg/L, respectively.
  
  
  CONCLUSIONS
  This method is suitable for clinical studies with coenzyme Q10 supplementation in various disease states where this lipid-antioxidant may be beneficial. We have applied this method to >300 plasma samples from coenzyme Q10 research studies in chronic haemodialysis patients and postsurgical patients.
authors.affiliation: Pharmacokinetics Laboratory, Department of Pharmaceutics, School of Pharmacy, University of Washington, Seattle, WA, USA.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Claessens
authors.affiliation: Department of Pharmacy, School of Pharmacy, University of Washington, Seattle, WA, USA Kidney Research Institute, Division of Nephrology, Department of Medicine, School of Medicine, University of Washington, Seattle, WA, USA.
authors.forename: Catherine K
authors.initials: CK
authors.lastname: Yeung
authors.affiliation: Pharmacokinetics Laboratory, Department of Pharmaceutics, School of Pharmacy, University of Washington, Seattle, WA, USA.
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Risler
authors.affiliation: Pharmacokinetics Laboratory, Department of Pharmaceutics, School of Pharmacy, University of Washington, Seattle, WA, USA.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Phillips
authors.affiliation: Kidney Research Institute, Division of Nephrology, Department of Medicine, School of Medicine, University of Washington, Seattle, WA, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Himmelfarb
authors.affiliation: Pharmacokinetics Laboratory, Department of Pharmaceutics, School of Pharmacy, University of Washington, Seattle, WA, USA Department of Pharmacy, School of Pharmacy, University of Washington, Seattle, WA, USA Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, WA, USA ds@uw.edu.
authors.forename: Danny D
authors.initials: DD
authors.lastname: Shen
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods*; D064368:Healthy Volunteers; D006801:Humans; D057230:Limit of Detection; D010084:Oxidation-Reduction; D013048:Specimen Handling; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014451:Ubiquinone; C024989:coenzyme Q10
keywords: UPLC-MS/MS; oxidized CoQ10; plasma concentrations; reduced Coq10; stability