Development of stable isotope dilution analyses for components of the vitamin B6 group in foods

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An insufficient supply with vitamins of the B6 group is assumed in all society over the world. As the eight B6 vitamers naturally occurring in foods reveal strongly varying bioavailability, knowledge on vitamer distribution in foods is essential for validated uptake data and accurate dietary recommendations. This is in particular crucial for glucosylated vitamers, which are highly abundant in foods of plant origin and show particularly low bioavailabilities. According to the current state of the art an accurate analysis of all vitamers is only possible by LC-MS. In this regard a bottleneck is the lacking availability of reference compounds for the glucysidic forms of pyridoxine. Besides this, a quantitation by LC-MS generally is hindered by matrix interferences. Therefore, the project presented here aims at chemical syntheses of 4- and 5-O-(beta-D-glucopyranosyl)-pyridoxine and analysis of all accurring B6 vitamers in foods. For quantitation of eight B6 vitamers the respective stable isotopologues will be synthesized and applied as internal standards in stable isotope dilution assays. Following a thorough validation, application of the method will be proved in a small-scale market survey. The method will serve in follow-up studies as the basis for a determination of B6 in blood plasma in order to assess accurately the bioavailability of the pyridoxine glucosides that will be characterized unambiguously here for the first time.