Characterization and Quantitation of Vitamin B₁₂ Compounds in Various Chlorella Supplements

Vitamin B₁₂ was determined and characterized in 19 dried Chlorella health supplements. Vitamin contents of dried Chlorella cells varied from <0.1 μg to approximately 415 μg per 100 g of dry weight. Subsequent liquid chromatography/electrospray ionization–tandem mass spectrometry analyses showed the presence of inactive corrinoid compounds, a cobalt-free corrinoid, and 5-methoxybenzimidazolyl cyanocobamide (factor IIIm) in four and three high vitamin B₁₂-containing Chlorella tablets, respectively. In four Chlorella tablet types with high and moderate vitamin B₁₂ contents, the coenzyme forms of vitamin B₁₂ 5′-deoxyadenosylcobalamin (approximately 32%) and methylcobalamin (approximately 8%) were considerably present, whereas the unnaturally occurring corrinoid cyanocobalamin was present at the lowest concentrations. The species Chlorella sorokiniana (formerly Chlorella pyrenoidosa) is commonly used in dietary supplements and did not show an absolute requirement of vitamin B₁₂ for growth despite vitamin B₁₂ uptake from the medium being observed. In further experiments, vitamin B₁₂-dependent methylmalonyl-CoA mutase and methionine synthase activities were detected in cell homogenates. In particular, methionine synthase activity was significantly increased following the addition of vitamin B₁₂ to the medium. These results suggest that vitamin B₁₂ contents of Chlorella tablets reflect the presence of vitamin B₁₂-generating organic ingredients in the medium or the concomitant growth of vitamin B₁₂-synthesizing bacteria under open culture conditions.