Determination of cobalamin (Vitamin B12) in selected microalgae and cyanobacteria products by HPLC-DAD

In the scope of vegetarian diets, cobalamin (CBL or vitamin B-12) remains a particular concern, as it is mostly absent from natural, vegetarian foods. As such, vegetarians must rely on supplementation or enriched food products, to fulfil their recommended daily intake of the vitamin. The potential of microalgae is of extreme importance in this context, given the fact that they may absorb exogenous CBL and display significant levels of the vitamin. Therefore, it is crucial to establish fast and reliable B-12 determination methods, to accurately characterize these products or ingredients and conclude about their role as CBL sources. To that extent, this work presents the application of the AOAC's final action method 2014.02 on the determination of total CBL in selected, commercial, microalgae and cyanobacteria powder samples. Four variants of Chlorella vulgaris, namely organic, smooth, white and honey, as well as Spirulina (Arthrospira platensis) were investigated. High-performance liquid chromatography coupled with ultraviolet (UV), diode-array detection (HPLC-DAD) was implemented in the analysis of microalgal extracts. After slight adaptation and optimisation of the extraction and analysis procedures, namely to allow lower sample amounts, it was determined that the different commercial Chlorella products, organic, smooth, white and honey have total CBL concentrations of 1063 +/- 158 mu g (100 g)(-1), 482 +/- 55 mu g (100 g)(-1), 681 +/- 87 mu g (100 g)(-1) and 660 +/- 68 mu g (100 g)(-1), respectively. Analysis of Spirulina did not yield any measurable levels of CBL in any of the purified extracts. Despite the obtained results displaying the same order of magnitude previously determined in similar microalgal products, these CBL values are amongst the highest concentrations found. Therefore, even considering the known limitations in bioaccessibility and bioavailability of CBL in microalgae, it is possible to conclude that these results stand for the inclusion of these products in vegetarian foods or as food supplements, as good potential sources of CBL, which is generally lacking in vegetarian diets.