Thermospray and electrospray mass spectrometry of flavocoenzymes. Analysis of riboflavin sulphates from sugar beet

Comprehensive and quantitative profiling of B vitamins and related compounds in the mammalian liver

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A validated method for quantification of 13 B vitamins and four related compounds in sheep liver.

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Limits of detection for the majority of analytes were within the range of 0.4–3.2 pmol/g.

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Simple sample extraction procedure with high throughput.

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Successfully applied to profile 1C major forms in 266 sheep liver samples.

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Potential for dietary and genetic studies in metabolic health and epigenetic gene regulation.

A method for the simultaneous quantification of B vitamins and related amines in one-carbon (1C) metabolism would benefit the study of diet and genetic/epigenetic regulation of mammalian development and health. We present a validated method for the simultaneous quantitative analysis of 13 B vitamers and four related 1C-pathway amine intermediates in liver using hydrophilic interaction chromatography (HILIC) coupled to electrospray ionization tandem mass spectrometry. Frozen sheep liver samples (50 mg) were homogenized in cold 50% acetonitrile containing 1% acetic acid with the addition of two isotope labelled internal standards. Hot acid hydrolysis was applied to release the protein-bound forms. The separation of 17 analytes was achieved using a pHILIC column with a total run time of 13 min. Detection was achieved in electrospray positive ionisation mode. Limits of detection for the majority of analytes were within the range of 0.4–3.2 pmol/g. The method was applied to 266 sheep liver samples and revealed that adenosylcobalamin, methylcobalamin, pyridoxic acid, flavin adenine dinucleotide and thiamine were the major forms of the B vitamers present with pyridoxal 5′-phosphate and thiamine pyrophosphate being detected at lower concentrations. Trimethylglycine and methylglycine were the predominant 1C-related amines measured. As anticipated, the B vitamin status of individuals varied considerably, reflecting dietary and genetic variation in our chosen outbred model species. This method offers a simple sample extraction procedure and provides comprehensive coverage of B vitamins coupled with good sensitivity and reliability.

Multianalyte quantification of vitamin B6 and B2 species in the nanomolar range in human plasma by liquid chromatography-tandem mass spectrometry

BACKGROUND

Homocysteine, a risk factor of cardiovascular disease, cognitive disorders, and pregnancy complications, exists at a point of metabolic convergence of several B vitamins, including vitamins B(6) and B(2) (riboflavin). Measurement of the various forms of these vitamins may be useful for the study of hyperhomocysteinemia as well as for the assessment of vitamin status.

METHODS

Plasma (60 microL) was deproteinized by mixing with an equal volume of 50 g/L trichloroacetic acid that contained d(2)-pyridoxal 5'-phosphate, d(3)-pyridoxal, and d(8)-riboflavin as internal standards. Pyridoxal (PL), pyridoxal 5'-phosphate (PLP), pyridoxine (PN), pyridoxine 5'-phosphate, pyridoxamine (PM), pyridoxamine 5'-phosphate, 4-pyridoxic acid (PA), riboflavin, flavin mononucleotide (FMN), and FAD were separated on a C(8) reversed-phase column, which was developed with an acetonitrile gradient in a buffer containing acetic acid and heptafluorobutyric acid. The analytes were detected by tandem mass spectrometry in the positive-ion mode.

RESULTS

The chromatographic run lasted 8 min. Within- and between-day CVs were 3%-20% and 6%-22%, respectively, and recoveries were 78%-163%. Limits of detection (signal-to-noise ratio = 5) were in the range 0.1-4.0 nmol/L, and the response was linear over several orders of magnitude. In samples from 94 healthy persons, we obtained median concentrations (nmol/L) of 35.4 for PLP, 16.9 for PL, 22.4 for PA, 10.3 for riboflavin, 7.5 for FMN, and 63.1 for FAD. PN and PM were also detected in some cardiovascular patients taking B(6) supplements.

CONCLUSIONS

This method based on liquid chromatography-tandem mass spectrometry measures all known plasma forms of vitamins B(6) and B(2), which span a wide range of polarity. The assay is characterized by simple sample processing with no derivatization, low sample volume requirement, and a short run time.