A new LC-MS assay for the quantitative analysis of vitamin K metabolites in human urine[S]

• Main Authors: Matthew G. McDonald, Catherine K. Yeung, Aaron M. Teitelbaum, Amanda L. Johnson, Shinya Fujii, Hiroyuki Kagechika, Allan E. Rettie
• Format: Article
• Language: English
• Published: Elsevier 2019-04-01
• Series: Journal of Lipid Research
• Subjects: beta-oxidation; omega-oxidation; liquid chromatography-mass spectrometry; menaquinone; phylloquinone
• Online Access: http://www.sciencedirect.com/science/article/pii/S0022227520326018

Vitamin K (VK), in both its phylloquinone and menaquinone forms, has been hypothesized to undergo ω- and β-oxidation on its hydrophobic side chain in order to generate the observed urinary metabolites, K acid I and K acid II, which are excreted primarily as glucuronide conjugates. Synthetic standards of K acid I, K acid II, and a putative intermediate metabolite, menaquinone (MK)1 ω-COOH, were used to develop and optimize a new atmospheric pressure negative chemical ionization LC-MS/MS assay for the quantitation of these compounds in urine from untreated individuals and subjects treated with a high dose VK supplement. VK catabolites were extracted from urine, deconjugated, and converted to their methyl ester derivatives using previously reported methodology. The assay showed a high degree of sensitivity, with limits of detection below 10–50 fmol of metabolite per milliliter of urine, as well as an inter-assay precision of 8–12%. Metabolite standards provided unambiguous evidence for MK1 ω-COOH as a new human urinary metabolite of VK. This assay provides a minimally invasive, highly sensitive, and specific alternative for monitoring VK status in humans.