Inactive corrinoid compounds

Spirulina tablets contain large amounts (127-244 pg/100 g weight) of B12 when assayed using microbiological method [28]. However, Herbert and Drivas [29] showed that most B12 found in Spirulina tablets comprise biologically inactive corrinoid compounds. Several studies [30,31] also indicate that these Spirulina corrinoids may not be bioavailable in manunals. To clarify whether Spirulina tablets contain active B12 or inactive corrinoid compounds, two corrinoid compounds (major, 83% and minor, 17%) were purified and then identified as pseudo-Bi2 and B12, respectively [30] (Fig. 1). 

Usual dietary sources of vitamin B12 are animal food products (meat, milk, eggs, and shellfish), but not plant food products. To evaluate whether foods contain true vitamin B12 or inactive corrinoids, vitamin B12 compounds were purified and characterized using TLC on silica gel. The Rf values of the unknown vitamin B12 compound, purified from an algal health food (Spmilina tablets) were identical to those of pseudo vitamin B12 (Rf values 0.14 and 0.42), but not to those of vitamin Bi2 (or 5,6-dimethylbenzimidazolyl cyanocobamide) (Rf values 0.23 and 0.56), benzimidazolyl cyanocobamide (Rf values 0.18 and 0.52), 5-dydroxybenzunida-zolyl cyanocobamide (Rf values 0.20 and 0.47), and p-cresolyl cyanocobamide (Rf values 0.38 and 0.62) by TLC on silica gel 60 with l-butanol-2-propanol-water (10 7 10 vol/vol) and 2-propanol-NH40H (28%)-water (7 1 2 vol/vol) as solvents, respectively. The results indicate that an inactive vitamin B12 compound (pseudovitamin B12) is predominant in Spirulina tablets. 

Substantial quantities of edible cyanobacteria are produced globally to meet the high demands of both food and pharmaceutical industries. These cyanobacteria contain substantial quantities of phycobiliproteins, of which phycocy-anin, in particular, has various therapeutic effects owing to the linear tetrapyrrole chromophore phycocyanobilin. Cyanobacteria can also synthesize macrocyclic tetrapyrrole corrinoid compounds. However, various edible cyanobacteria contain substantial quantities of inactive pseudo-Bi2 rather than active Bi2- To overcome this nutritional defect of edible cyanobacteria, it is vital to determine the genetic, biochemical, and physiological properties of pseudo-Bi2-... 

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