Quantitative determination of plasma vitamin K1 by high-performance liquid chromatography coupled to isotope dilution tandem mass spectrometry

Electrochemical biosensor based on NAD(P)H-dependent quinone reductase for rapid and efficient detection of vitamin K3

Vitamin K refers to a group of vitamins that play an important role in blood coagulation and regulation of bone and vascular metabolism. However, vitamin K3 may give severe side effects in animal and humans when improperly added to food and feed due to its toxicity. Here, an electrochemical biosensor, based on the YaiB NADPH-dependent quinone reductase from Lactococcus lactis (YaiB), was developed to achieve rapid and redox probe-free detection of vitamin K3. First, the ability of the carbon electrode to distinguish between 1,4-benzoquinone and hydroquinone was demonstrated. Then, we engineered YaiB to work as a bioreceptor immobilized at the electrode and its sensitivity and specificity to reduce vitamin K3 were demonstrated. Finally, to demonstrate the practical potential of the biosensor, we tested it directly in spiked milk samples, achieving 15-minute quantification of the vitamin K3. The limit of detection was 0.87 µM and 4.1 µM in buffer and milk, respectively.

Analysis of vitamin K1 and major K2 variants in rat/human serum and lipoprotein fractions by a rapid, simple, and sensitive UHPLC-MS/MS method

Determination of the various forms of vitamin K, which are involved in coagulation and other physiological processes in humans, is challenging and no standardized method is yet available. Therefore, a reliable and practical method was developed to quantify vitamin K levels in serum and additionally in lipoprotein fractions to clarify its distribution. The LC-MS/MS method for the determination of vitamin K1 and the three main isoforms of vitamin K2 (MK-4, MK-7, MK-9) was combined with a gradient ultracentrifugation technique to allow the separation of lipoprotein fractions. The chromatographic separation was carried out on a Kinetex™ C18 column using a mobile phase consisting mainly of methanol. The target analytes were detected by electrospray ionization mass spectrometry. The separation of all four substances was achieved after a simple sample preparation technique based on miniaturized liquid-liquid extraction. Our method of only 8.5 min revealed the levels of the major forms of vitamin K in 59 human and 12 rat sera and confirmed our hypothesis that vitamin K is primarily (about 50 %) found in the high-density lipoprotein fraction. The median concentrations of vitamin K1, MK-4, MK-7, and MK-9 were found to be 1.19, 2.98, 0.43, and < 0.71 nmol/L in human serum and 1.74, 6.75, less than 0.2, and less than 0.5 nmol/L in rat serum, respectively.

Rapid simultaneous determination of 7 fat-soluble vitamins in human serum by ultra high performance liquid chromatography tandem mass spectrometry

Accurate detection of vitamins is critically important for clinical diagnosis, metabolomics and epidemiological studies. However, the amounts of different vitamins vary dramatically in human serum. It is a challenge to achieve simultaneous detection of multiple vitamins rapidly. Herein, we developed and validated a sensitive and specific method using ultra high-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) for simultaneous quantification of 7 fat-soluble vitamins (FSVs) across their physiological concentrations in serum for the first time, which was subjected to protein precipitation, liquid-liquid extraction to an organic phase, evaporation to dryness and reconstitution with acetonitrile. In the present procedure, retinol (vitamin A), ergocalciferol (25-OH-D2), cholecalciferol (25-OH-D3), α-tocopherol (vitamin E), phylloquinone (vitamin K1), menatetrenone-4 (MK-4), and menaquinone-7 (MK-7) were detected in one analytical procedure for the first time within 5.0 min by triple quadrupole tandem mass spectrometry. The limit of quantification (LOQ) for vitamin A was 10.0 ng mL-1, LOQs for 25-OH-D2 and 25-OH-D3 were 1.0 ng mL-1, LOQ for vitamin E was 100.0 ng mL-1, and LOQs for vitamin K1, MK-4 and MK-7 were 0.10 ng mL-1, respectively, with a correlation (R2) of 0.995-0.999. Recoveries ranged from 80.5% to 118.5% and the intra-day and inter-day coefficients of variance (CVs) were 0.72-8.89% and 3.2-9.0% respectively. The method was validated according to the European Medicines Agency (EMA) and U.S. Food and Drug guidelines and C62-A on bioanalytical methods, and was used for clinical routine determination.

Liquid chromatography-tandem mass spectrometry in fat-soluble vitamin deficiency

Fat-soluble vitamins, including vitamins A, D, E, and K, are essential for maintaining normal body function and metabolism. Fat-soluble vitamin deficiency may lead to bone diseases, anemia, bleeding, xerophthalmia, etc. Early detection and timely interventions are significant for preventing vitamin deficiency-related diseases. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is developing into a potent instrument for the precise detection of fat-soluble vitamins due to its high sensitivity, high specificity, and high resolution.

New Insights into Vitamin K-From Its Natural Sources through Biological Properties and Chemical Methods of Quantitative Determination

Vitamin K is one of the many health-promoting substances whose impact on the human body has been underestimated until recently. However, recently published research results have changed this situation, prompting some researchers to consider it a new panacea for diseases of old age. The result is a significant increase in interest in the accurate analysis of vitamin K in various types of samples, ranging from food, through dietary supplements, to biological matrices and clinical trials, both observational and interventional. This review summarizes the current state of knowledge about the proven and speculated biological activity of vitamin K and its importance for the world's aging societies, including the methods used for its isolation and analysis in various matrices types. Of all the analytical methods, the currently preferred methods of choice for the direct analysis of vitamin K are chromatographic methods, in particular liquid chromatography-tandem mass spectrometry. This technique, despite its sensitivity and selectivity, requires an appropriate stage of sample preparation. As there is still room for improvement in the efficiency of these methods, especially at the sample preparation stage, this review shows the directions that need to be taken to make these methods faster, more efficient and more environmentally friendly.

Determination of Vitamins K1, K2 MK-4, MK-7, MK-9 and D3 in Pharmaceutical Products and Dietary Supplements by TLC-Densitometry

Vitamin K is a group of lipophilic molecules. Forms of vitamin K play an essential role in the activation of specific proteins involved in blood clotting cascade or bone metabolism. Another molecule belonging to the fat-soluble vitamins group that also plays an important role in calcium metabolism is vitamin D3. The dietary supplements containing vitamins K and D3 are one of the most frequently consumed by patients. The objective of this work was to develop a simple, fast and sensitive thin-layer chromatography (TLC)-densitometric procedure for the simultaneous quantitative analysis of vitamins K and D3 in pharmaceutical products and dietary supplements. The analysis of vitamins was performed on the silica gel RP-18 F₂₅₄s plates with methanol-ethanol-isopropanol in a volume ratio of 15:1:4 as a mobile phase. The densitometric measurements were made at 254 nm. The method was validated by checking the specificity, linearity, precision, recovery, limit of detection, limit of quantification and robustness in accordance with International Conference on Harmonization (ICH) guidelines. The method was shown to be specific, accurate (recoveries were from 95.78 to 104.96%), linear over the tested range (correlation coefficient, exceeding 0.99), and precise (precision and intermediate precision RSD below 2.70% for all analytes). The satisfactory results of the validation of the method indicate that it can be used in the quality control of dietary supplements and pharmaceutical products containing vitamins K and D3.

Cis and trans isomers of the vitamin menaquinone-7: which one is biologically significant?

Recently, several studies have indicated that an adequate intake of menaquinone-7 (MK-7) offers numerous health benefits. However, the low availability of MK-7 in the diet necessitates the development of dietary supplements or functional food products to complement natural food sources and meet the daily intake requirements. Like most biological molecules, MK-7 can exist as geometric isomers that can occur in the cis, trans, and cis/trans forms; however, only the all-trans form is biologically significant. MK-7 is traditionally produced through bacterial fermentation, but various synthetic preparations have lately become available. The isomer composition in the final product is influenced by numerous factors, including the methods of production and purification, as well as particular environmental and storage conditions. The MK-7 profile obtained from the various production methods has not yet been elucidated, and the ideal method for the synthesis of the all-trans form of the vitamin is also debatable. Consequently, the quantification of the MK-7 profile of various products is necessary to develop an understanding of the factors that influence the proportion of isomers that are obtained in different preparations. Several possible methods exist for the quantification of MK-7 isomers, and of these, liquid chromatography in conjunction with mass spectrometry techniques appears to be the most promising. Evaluation of the isomer composition is an important consideration, as only the all-trans form sustains biological activity. Furthermore, knowledge of the prominent factors that influence the MK-7 composition may also enable their manipulation to obtain a more favorable MK-7 profile in the final product.

Laboratory assessment of vitamin K status

Vitamin K is required for the ɣ-carboxylation of specific glutamic acid residues within the Gla domain of the 17 vitamin K-dependent proteins (VKDPs). The timely detection and correction of vitamin K deficiency can protect against bleeding. Vitamin K also plays a role in bone metabolism and vascular calcification. Patients at increased risk of vitamin K deficiency include those with a restricted diet or malnutrition, lipid malabsorption, cancer, renal disease, neonates and the elderly. Coagulation assays such as the prothrombin time have been used erroneously as indicators of vitamin K status, lacking sufficient sensitivity and specificity for this application. The measurement of phylloquinone (K1) in serum is the most commonly used marker of vitamin K status and reflects abundance of the vitamin. Concentrations <0.15 µg/L are indicative of deficiency. Disadvantages of this approach include exclusion of the other vitamin K homologues and interference from recent dietary intake. The cellular utilisation of vitamin K is determined through measurement of the prevalence of undercarboxylated VKDPs. Most commonly, undercarboxylated prothrombin (Protein Induced by Vitamin K Absence/antagonism, PIVKA-II) is used (reference range 17.4–50.9 mAU/mL (Abbott Architect), providing a retrospective indicator of hepatic vitamin K status. Current clinical applications of PIVKA-II include supporting the diagnosis of vitamin K deficiency bleeding of the newborn, monitoring exposure to vitamin K antagonists, and when used in combination with α-fetoprotein, as a diagnostic marker of hepatocellular carcinoma. Using K1 and PIVKA-II in tandem is an approach that can be used successfully for many patient cohorts, providing insight into both abundance and utilisation of the vitamin.

A concise review of quantification methods for determination of vitamin K in various biological matrices

Vitamin K is an essential nutrient in the body and involved in numerous physiological and pathophysiological functions. Both the lack and surplus of vitamin K can put human health at risk. Therefore, it becomes necessary to monitor vitamin K concentrations in different biomatrices through establishing sensitive and specific analytical methods. This review collectively describes an updated overview of the sample pretreatment methodologies and methods for quantitative determination of vitamin K that have been used in last two decades. High Performance Liquid Chromatography (HPLC) is commonly utilized as a standard for separation of vitamin K in combination with different detection including spectroscopic, spectrometric, fluorometric and mass spectroscopy. Recent progress in sample pretreatment technologies and quantitation methodologies have enhanced the ability to identify and quantitate vitamin K in biomatrices to further advance our understanding of the role of this vitamin in human health and disease.

A simple, sensitive, and high-throughput LC-APCI-MS/MS method for simultaneous determination of vitamin K1, vitamin K1 2,3-epoxide in human plasma and its application to a clinical pharmacodynamic study of warfarin

Warfarin exerts its anticoagulation activity by blocking the vitamin K-epoxide cycle. A quantitative understanding of how warfarin and related genes interact with the vitamin K-epoxide cycle and the associated change of coagulation activity in the human body may help study the pharmacodynamics of warfarin. The plasma concentration of vitamin K₁ (VK₁) and vitamin K₁ 2,3-epoxide (VK₁O) could reflect the status of vitamin K-epoxide cycle. However, their determination is a challenging task due to their extremely low concentrations in human plasma and the severe interferences caused by co-extracted lipids. In this study, we developed an LC-APCI-MS/MS method for the simultaneous determination of VK₁ and VK₁O in human plasma using stable deuterium-labeled vitamin K₁ (vitamin K₁-d7) as the internal standard (IS). Plasma samples were prepared through protein denaturation followed by one-step liquid extraction with cyclohexane. Chromatographic separation of analytes from isobaric interferences and endogenous ion suppressor was performed on a Synergi Hydro-RP column (150 mm × 4.6 mm, 4 μm) under the reversed-phase condition with isocratic elution. The selective reaction monitoring (SRM) transitions were chosen as m/z = 451.5→187.3 for VK₁, m/z = 467.5→161.2 for VK₁O, and m/z = 458.6→194.3 for IS in APCI positive mode. The assay was linear in the range of 100-10,000 pg/mL for the two analytes and achieved considerable extraction recoveries (87.8-93.3%, 91.0-96.9%, and 92.0% for VK₁, VK₁O, and IS, respectively), negligible matrix effects (93.6-96.0%, 96.3-100.1%, and 95.5%), and high selectivity with a small sample volume requirement (0.2 mL) and short run time (15 min). The validated method was successfully applied in a clinical pharmacodynamic study of warfarin, and the clotting activity was found to be negatively correlated with the plasma concentration ratio of VK₁O to VK₁.

A Review of the Extraction and Determination Methods of Thirteen Essential Vitamins to the Human Body: An Update from 2010

Vitamins are a class of essential nutrients in the body; thus, they play important roles in human health. The chemicals are involved in many physiological functions and both their lack and excess can put health at risk. Therefore, the establishment of methods for monitoring vitamin concentrations in different matrices is necessary. In this review, an updated overview of the main pretreatments and determination methods that have been used since 2010 is given. Ultrasonic assisted extraction, liquid–liquid extraction, solid phase extraction and dispersive liquid–liquid microextraction are the most common pretreatment methods, while the determination methods involve chromatography methods, electrophoretic methods, microbiological assays, immunoassays, biosensors and several other methods. Different pretreatments and determination methods are discussed.

Vitamin K plasma levels determination in human health

Vitamin K (phylloquinone or vitamin K1 and menaquinones or vitamin K2) plays an important role as a cofactor in the synthesis of hepatic blood coagulation proteins, but recently has also aroused an increasing interest for its action in extra-hepatic tissues, in particular in the regulation of bone and vascular metabolism. The accurate measurement of vitamin K status in humans is still a critical issue. Along with indirect assays, such as the undercarboxylated fractions of vitamin K-dependent proteins [prothrombin, osteocalcin (OC), and matrix gla protein], the direct analysis of blood levels of phylloquinone and menaquinones forms might be considered a more informative and direct method for assessing vitamin K status. Different methods for direct quantification of vitamin K serum levels are available. High-performance liquid chromatography (HPLC) methods coupled with post-column reduction procedures and fluorimetric or electrochemical detection are commonly used for food and blood analysis of phylloquinone, but they show some limitations when applied to the analysis of serum menaquinones because of interferences from triglycerides. Recent advancements include liquid chromatography tandem mass spectrometry (LCMS/MS) detection, which assures higher specificity. The optimization and standardization of these methods requires specialized laboratories. The variability of results observed in the available studies suggests the need for further investigations to obtain more accurate analytical results.

Measurement of plasma vitamin K1 (phylloquinone) and K2 (menaquinones-4 and -7) using HPLC-tandem mass spectrometry

BACKGROUND

Given the growing interest in the health benefits of vitamin K, there is great need for development of new high-throughput methods for quantitative determination of vitamin K in plasma. We describe a simple and rapid method for measurement of plasma vitamin K1 (phylloquinone [PK]) and K2 (menaquinones [MK]-4 and -7). Furthermore, we investigated the association of fasting plasma vitamin K with functional vitamin K insufficiency in renal transplant recipients (RTR).

METHODS

We used HPLC-tandem mass spectrometry with atmospheric pressure chemical ionization for measurement of plasma PK, MK-4, and MK-7. Solid-phase extraction was used for sample clean-up. Mass spectrometric detection was performed in multiple reaction monitoring mode. Functional vitamin K insufficiency was defined as plasma desphospho-uncarboxylated matrix Gla protein (dp-ucMGP) >500 pmol/L.

RESULTS

Lower limits of quantitation were 0.14 nmol/L for PK and MK-4 and 4.40 nmol/L for MK-7. Linearity up to 15 nmol/L was excellent. Mean recoveries were >92%. Fasting plasma PK concentration was associated with recent PK intake (ρ=0.41, p=0.002) and with plasma MK-4 (ρ=0.49, p<0.001). Plasma PK (ρ=0.38, p=0.003) and MK-4 (ρ=0.46, p<0.001) were strongly correlated with plasma triglyceride concentrations. Furthermore, we found that MK-4-triglyceride ratio, but not PK-triglyceride ratio, was significantly associated with functional vitamin K insufficiency (OR 0.22 [0.07-0.70], p=0.01) in RTR.

CONCLUSIONS

The developed rapid and easy-to-use LC-MS/MS method for quantitative determination of PK, MK-4, and MK-7 in human plasma may be a good alternative for the labor-intensive and time-consuming LC-MS/MS methods and enables a higher sample throughput.

Development of isotope dilution-liquid chromatography/tandem mass spectrometry for the accurate determination of trans- and cis-vitamin K1 isomers in infant formula

A method based on isotope dilution-liquid chromatography/tandem mass spectrometry (ID-LC/MS/MS) using a C30 column has been developed for the separate and accurate determination of trans- and cis-vitamin K₁ in infant formula. Vitamin K₁ and the deuterium-labeled internal standard eluted at slightly different retention times experiencing different matrix effects, and this possibly resulted in biased measurement. The matrix effect profiles obtained from post-column infusion experiments showed that atmospheric pressure chemical ionization (APCI) was less susceptible to matrix effects near the retention time than electrospray ionization (ESI); therefore, APCI was used in this study. The developed method was validated by measuring fortified samples, and the results agreed with the gravimetric values. Its repeatability and reproducibly were within 2% relative standard deviation. The relative expanded uncertainty was approximately 5%, indicating that the method was of higher-order metrological quality as a reference method.

Reactive paper spray mass spectrometry for in situ identification of quinones

RATIONALE

The polycyclic aromatic hydrocarbons quinones are reported to be harmful and could cause mutations and cancer via the generation of reactive oxygen species through their redox cycle in human body. For detection by gas chromatography and high-performance liquid chromatography mass spectrometry (MS), sample pretreatments and chromatographic separation prior to MS are generally required, which makes the whole analytical process laborious and time-consuming, resulting in difficulties for fast screening targets from complicated matrices. Thus facile, rapid and reliable MS methods for detection of quinones in complicated matrices are in great demand.

METHODS

Reactive paper spray mass spectrometry is reported for rapid identification and quantification of quinones in complicated matrices. The method is based on an in situ derivatization reaction between cysteamine and quinones prior to analysis with paper spray mass spectrometry. With the addition of an easily charged chemical tag, the ionization efficiency of analysts is greatly improved. Due to the high ionization efficiency of the drivatives, quinones in complicated matrices could be detected rapidly without any pretreatment.

RESULTS

Under the optimized experimental conditions, the linear dynamic ranges for both 1,4-benzoquinone and 1,4-naphthoquinone are 0.4-40 ng and that for 1,4-anthraquinone is 0.4-20 ng. Limits of detection for these three analytes were measured to be 160, 40 and 200 pg using methyl-p-benzoquinone as internal standard. The capability to conduct MS analysis under ambient pressure is illustrated by identification of 1,4-naphthoquinone and 1,4-anthraquinone in raw urine, raw serum and cell culture medium.

CONCLUSIONS

Reactive paper spray could be applied to fast screening of quinones from complicated matrices. Therefore, we believe that reactive paper spray mass spectrometry might be potentially useful in the fields of environmental sciences, metabolomics and clinic analysis.

Review article: The nutritional and pharmacological consequences of obesity surgery

BACKGROUND

Obesity surgery is acknowledged as a highly effective therapy for morbidly obese patients. Beneficial short-term effects on common comorbidities are practically undisputed, but a growing data pool from long-term follow-up reveals increasing evidence of potentially severe nutritional and pharmacological consequences.

AIMS

To assess the prevalence, causes and symptoms of complications after obesity surgery, to elucidate and compare therapy recommendations for macro- and micronutrient deficiencies, and to explore surgically-induced effects on drug absorption and bioavailability, discussing ramifications for long-term therapy and prophylaxis.

METHODS

PubMed, Embase and MEDLINE were searched using terms including, but not limited to, bariatric surgery, gastric bypass, obesity surgery and Roux-en-Y, coupled with secondary search terms, e.g. anaemia, micronutrients, vitamin deficiency, bacterial overgrowth, drug absorption, pharmacokinetics, undernutrition. All studies in English, French or German published January 1980 through March 2014 were included.

RESULTS

Macro- and micronutrient deficiencies are common after obesity surgery. The most critical, depending on surgical technique, are hypoalbuminemia (3-18%) and deficiencies of vitamins B1 (≤49%), B12 (19-35%) and D (25-73%), iron (17-45%) and zinc (12-91%). Many drugs commonly administered to obese patients (e.g. anti-depressants, anti-microbials, metformin) are subject to post-operative and/or PPI-associated changes affecting bioavailability and absorption.

CONCLUSIONS

Complications are associated with pre-operative and/or post-operative malnutrition or procedure-related changes in intake, absorption and drug bioavailability. The high prevalence of nutrient deficiencies after obesity surgery makes life-long nutritional monitoring and supplementation essential. Post-operative changes to drug absorption and bioavailability in bariatric patients cast doubt on the validity of standard drug dosage and administration recommendations.

Does menaquinone participate in brain astrocyte electron transport?

Quinone compounds act as membrane resident carriers of electrons between components of the electron transport chain in the periplasmic space of prokaryotes and in the mitochondria of eukaryotes. Vitamin K is a quinone compound in the human body in a storage form as menaquinone (MK); distribution includes regulated amounts in mitochondrial membranes. The human brain, which has low amounts of typical vitamin K dependent function (e.g., gamma carboxylase) has relatively high levels of MK, and different regions of brain have different amounts. Coenzyme Q (Q), is a quinone synthesized de novo, and the levels of synthesis decline with age. The levels of MK are dependent on dietary intake and generally increase with age. MK has a characterized role in the transfer of electrons to fumarate in prokaryotes. A newly recognized fumarate cycle has been identified in brain astrocytes. The MK precursor menadione has been shown to donate electrons directly to mitochondrial complex III.

HYPOTHESIS

Vitamin K compounds function in the electron transport chain of human brain astrocytes.

Influence of CYP4F2 polymorphisms and plasma vitamin K levels on warfarin sensitivity in Japanese pediatric patients

The aim of this study was to reveal the contribution of CYP4F2, CYP2C9, and VKORC1 genetic polymorphisms on the pharmacokinetics and pharmacodynamics of warfarin in Japanese pediatric patients. Genetic analyses of CYP4F2 (rs2108622), CYP2C9 (*2 and *3), and VKORC1 (-1639G>A) were performed, and plasma unbound warfarin, vitamin K1 (VK1), and menaquinone-4 (MK-4) concentrations were determined in 37 Japanese pediatric patients. The patients with CYP4F2 variant alleles C/T and T/T scored significantly lower values for the warfarin sensitivity index (INR/Cpss) and had significantly higher plasma concentrations of MK-4 than patients with the CYP4F2 allele C/C. Moreover, the plasma MK-4 concentration was negatively correlated with the warfarin sensitivity index. In contrast, the VKORC1 genetic polymorphism did not influence the warfarin sensitivity index. In patients with the CYP2C9 *3 allele, the unbound oral clearance values (normalized to body surface area) for S-warfarin were found to be significantly lower than in patients with the wild-type allele. In conclusion, CYP4F2 genetic polymorphism and plasma MK-4 concentration influence the pharmacodynamics of warfarin, suggesting a mechanism though which CYP4F2 genotype affects warfarin dose.