Abstract
A novel application of the liquid chromatography method combined with the triple quadrupole tandem mass spectrometry method was developed for the quantification of vitamin K1 and two forms of vitamin K2 (menaquinone-4, menaquinone-7) in human serum. Total chromatography time for each run was 9 min. Time required for the sample pretreatment procedures was approximately 4 h. The coefficients of variation (CVs) of intra-assay were 10.4%, 3.2 % and 2.3% for vitamin K1 in three levels of quality control samples; were 14.3%, 3.2% and 6.7% for menaquinone-4; and were 11.1%, 6.0% and 7.0% for menaquinone-7. The inter-assay CVs were 12.8%, 11.3% and 7.4% for vitamin K1; were 15.2%, 9.2% and 8.7% for menaquinone-4; and were 13.2%,11.1% and 7.2% for menaquinone-7. No interference was found between K1, menaquinone-4 and menaquinone-7, nor any deuterated internal standards. This method was then used to determine reference values for Caucasian populations of central European origin. Samples were measured from 191 healthy volunteers (51.2 ± 16.2 years (mean ± SD)) and the values concerning K1 were 0.044–1.357 ng/mL for women and 0.030–1.214 ng/mL for men. The values for menaquinone-4 and menaquinone-7 did not exhibit any differences between women and men, and were 0.050–1.598 and 0.074–0.759 ng/mL, respectively.
Highlights
Vitamin K is a cofactor for enzymatic modification of glutamic acid residues (Glu) to gamma-carboxyglutamic acid residues (Gla) in vitamin K-dependent Gla proteins
Our LC–MS/MS method for analysis of K1, MK-4 and MK-7 in human serum has been successfully validated following the criteria of the U.S Food and Drug Administration (FDA) (2013)
Calibration curves were established by plotting the peak area ratios K1, MK-4 and MK-7 against IS at 10-point concentrations
Summary
Vitamin K is a cofactor for enzymatic modification of glutamic acid residues (Glu) to gamma-carboxyglutamic acid residues (Gla) in vitamin K-dependent Gla proteins. These Gla proteins are necessary for hemostasis, bone metabolism, vascular calcification and cell proliferation. Vitamin K1 is the main form of vitamin K in the Western diet (about 90%), whereas menaquinones make up about 10%. This form of vitamin K is important mainly for blood coagulation. The main functions of vitamin K2 were discovered to be bone metabolism, vascular calcification and cell proliferation. Vitamins K2, K3, K4 and K5 have been shown to have anticancer effects (Fu et al, 2009; Jiang et al, 2013; Lee et al, 2015; Nakaoka et al, 2015; Osman, El-Abd & Nasrallah, 2016; EFSA NDA Panel (EFSA Panel on Dietetic Products, Nutrition and Allergies), 2017)
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