HPLC analysis of vitamin B6 in foods

Abstract

The objective of this work was to evaluate the methods for determination of vitamin B6 in foods. To achieve this, the literature review focused on sample treatment and liquid chromatographic analysis of vitamin B6 related compounds. In the experimental part, the chosen sample pretreatment and the high-performance liquid chromatographic (HPLC) method were validated, and used to produce vitamin B6 data on various food items commonly consumed in Finland. The main emphasis of the sample treatment was on the extraction efficiency and the maintenance of the original concentration profile of the vitamers. Several acid extraction procedures were tested for this purpose. Perchloric acid was chosen as the extraction agent. Routine food analysis was then performed using dilute ice-cold perchloric acid extraction followed by an internally standardized ion-paired reversed-phase liquid chromatography. Food samples were hydrolyzed with takadiastase and alkaline phosphatase enzymes, phosphorylated and glycosylated vitamers were quantitated before and after the enzymatic digestion. This procedure enabled the extraction of vitamin B6 compounds in their intact forms, and the measurement of free, phosphorylated and glycosylated forms. The maintenance of the concentration profile of the vitamers was verified by using 14C -labeled pyridoxal 5'-phosphate in the examination of the extraction procedure. The extraction efficiency and laboratory performance were confirmed by interlaboratory studies. Up-to-date data on vitamin B6 content of about fifty common food items was produced. The data includes the results from meat and poultry, fish and fish product, dairy product, cereal and vegetable, and ready-to-eat food samples. Free and phosphorylated vitamin B6 compounds were measured in all food groups, and the glycosylated vitamer fraction was analyzed in all plant-derived foods. The results obtained in this work showed that vitamin B6 content of nearly all foods of plant origin was mainly comprised of glycosidically bound pyridoxine derivatives. These bound analytes are normally not taken into account in traditional analytical methods, and food composition tables lack the data of glycosylated pyridoxine. The role of the glycosylated pyridoxines need to be clarified in terms of their analytical and physiological nature. If, as it is currently assumed, the availability of the bound forms is limited for humans, the role of vegetables, cereals and other foods of plant origin as a source of vitamin B6, as well as the analytical methods should be reassessed.;

Identification and characterization of a pyridoxal reductase involved in the vitamin B6 salvage pathway in Arabidopsis

“…The current model for the salvage pathway is derived from studies in E. coli, which produces PNP de novo. It is possible that plants, which produce PLP de novo but produce PN as the predominant vitamer (Ollilainen 1999), have an alternate means of PN synthesis not found in E. coli, perhaps directly from PLP rather than via dephosphorylation of PLP followed by PL reduction. Further research is needed to understand the complexity of the salvage pathway in plants.…”

“…Since PLP is the active cofactor, most studies have focused on its production from the other vitamers and comparatively little is known about reactions that convert PL or PLP to the other vitamers. In a study of B6 vitamer content in food, Ollilainen found that the major vitamer present in plant-derived foods is usually PN, either free or glycosylated (Ollilainen 1999). Thus plants must have an efficient system for producing PN.…”

Strategies for vitamin B6 biofortification of plants: a dual role as a micronutrient and a stress protectant

“…The bioavailability of vitamin B6 derived from plant food sources is also an important factor influencing adequate intake ( Figure 1 ). Plants contain multiple B6 vitamers and a substantial fraction of vitamin B6 is present as pyridoxine-5 ′ -β- D -glucoside (PN-glucoside; Gregory and Ink, 1987; Ollilainen, 1999; Figure 1 ). While PN, PL, and PM and their phosphorylated derivatives are fully bioavailable from plant food, PN-glucoside is only 50% bioavailable (Gregory, 2012; Figure 1 ).…”

Boron detection and quantification based on the absorption spectra of pyridoxine and its boron complex

“…3g-i) because the molar absorptivity of the complex is lower than that of pyridoxine under alkaline conditions. [20] Additionally, the absorption peak experienced a blue shift at the higher pH. In the neutral range, the form of free pyridoxine is different from that in the complex (Fig.…”