486 VITAMIN Bi2 



ing pigments belonging to the vitamin B12 group. Two of these pigments 

 were obtained in crystalline form and corresponded to the cyano and hy- 

 droxo forms, thereby bearing the same relationship to each other as vitamin 

 B12 does to vitamin Bi2b. Although the microbiological potency of these 

 forms for L. leichmannii and L. laclis Dorner was approximately that of 

 vitamin B12, the pigments were totally inactive for growth of chicks and in 

 the rat antihemorrhagic kidney test. For some strains of L. acidophilus 

 these compounds, designated pseudovitamin B12, were more active than 

 vitamin B12. This definitely higher potency for these lactobacilli opposes 

 the view that the pseudovitamin B12 compounds serve as precursors to 

 animal-active forms of vitamin B12. Dion et al}^ found evidence from ex- 

 amination of products resulting from acid degradation studies that pseudo- 

 vitamin B12 differed from vitamin B12 solely in the occurrence of adenine 

 instead of 5 , 6-dimethylbenzimidazole in the nucleotide portion of the mole- 

 cule. 



A third group^^ reported that a new form of vitamin B12 was produced 

 in rat feces by feeding 100 mg. of cobalt sulfate per kilogram of diet. This 

 fecal form of vitamin B12 was inactive for rat growth but had activity for 

 L. leichmannii and chicks similar to vitamin B12. 



In a later report, these workers named this fecal form of vitamin B12 , 

 vitamin Bi2f }^^ A crude preparation of vitamin Bi2f gave a spot on being 

 chromatographed on paper which had the same Rf value as Pfiffner's 

 pseudovitamin B12 . In contrast to their earlier report, they found that this 

 crude preparation does not possess growth-promoting activities for chicks. 

 A substance resembling vitamin Bi2f chromatographically was found to 

 be present in the feces of several farm animals and man. 



The recent reports of the University of Reading group^*^' "■ ^ clarified 

 much of the confusion regarding forms of vitamin B12 which differ from 

 vitamin B12 in the cobalamin part of the molecule. This group prepared 

 extremely pure samples of factors A, B, C, and pseudovitamin B12 . Follow- 

 ing the published directions, they also prepared a vitamin Biof concentrate. 

 Using paper ionophoresis to purify and characterize the various substances, 

 Holdsworth of the University of Reading group found that vitamin Bi2f 

 is a crude mixture of factor A and pseudovitamin B12 . Crystalline prepara- 

 tions of pseudovitamin B12 also contained factor A. Vitamin Bijm concen- 



2^ H. W. Dion, D. G. Calkins, and J. J. Pfiffner, J. Am. Chem. Soc. 74, 1108 (1952). 

 " U. J. Lewis, D. V. Tappan, and C. A. Elvehjem, J. Biol. Chem. 194, 539 (1952). 

 26" U. J. Lewis, D. V. Tappan, and C. A. Elvehjem, /. Biol. Chem. 199, 517 (1952). 

 "b E. S. Holdsworth, Nature 171, 148 (1953). 

 260 J. E. Ford, E. S. Holdsworth, S. L. Kon, and J. W. G. Porter, Nature 171, 150 



(1953). 

 26<i J. E. Ford, Nature 171, 149 (1953). 



