16 THE BIOCHEMISTRY OF B VITAMINS 



"Vitamin 5i 3 " represents a growth factor for rats which has been ob- 

 tained in highly concentrated form by Novak and Hauge. 39 The concen- 

 trate prepared was effective for rats at a level of 2 /^g per day and gave 

 a maximum response when 10 txg per day were administered. Its ultra- 

 violet absorption curve showed a maximum at 2820 A, and it exhibited 

 fluorescence. The material was readily soluble not only in water but also 

 in acetone, ethanol, ether, chloroform and benzene. If this substance 

 becomes established as a member of the B family of vitamins, it will be 

 unique with respect to its solubilities. This fact emphasizes the undesir- 

 ability of using solubility as a criterion for classifying vitamins. 



"Vitamin Bu,'' a crystalline substance having high growth-promoting 

 activity on reticulocytes and tumor cells in vitro and on the anemia in 

 rats induced by sulfathiazole administration, has been reported by Norris 

 and Majnarich. 40 It was isolated from urine and contains 19.6 per cent 

 nitrogen, 4 per cent phosphorus and no cobalt, and is thought to be func- 

 tionally related to folic acid. 41 



The literature contains numerous references to additional growth sub- 

 stances for microorganisms and animals which are potentially members 

 of the B vitamin family. However, neither their concentration nor char- 

 acterization has proceeded far enough to justify individual discussion.* 

 The history of the discovery and identification of individual B vitamins 

 is replete with nutritional factors, often designated by letter names and 

 numbers, which are more or less composite in nature and which have 

 remained poorly defined indefinitely. When a new growth substance is 

 identified and obtained in crystalline form, usually by the help of micro- 

 biological tests, confusion with respect to various nutritional factors pre- 

 viously discovered in animal work tends to be dispelled. 



Bibliography 



1. Williams, R. J., "A.A.A.S. Research Conference on Cancer," Science Press Print- 



ing Co., Lancaster, Pa., 1945, pp. 253-66. 



2. Williams, R. J., "Vitamins and Hormones," Vol. I, Academic Press, Inc., New 



York, N. Y., 1943, p. 231. 



3. Williams, R. R., Ergeb. Vitamin-Hormonjorsch., 1, 213-62 (1938). 



4. Rosenberg. H. R., "Chemistry and Physiology of the Vitamins," Interscience 



Publishers, New York, N. Y., 1942, pp. 155-70. 



* Since the above was written the concentration of three additional potential 

 members of the B vitamin family has been accomplished: Folinic acid (citrovorium 

 factor), Bond, T. J., Bardos, T. J., Sibley, M. and Shive, W., J. Am. Chem. Soc. 71, 

 3852 (1949) and Bardos, T. J , Bond, T. J., Humphreys, J. and Shive, W., ibid.; the 

 Lactobacillus bulgaricus factor, Williams, W. L., Hoff-Jo'rgensen, E. and Snell, E. E., 

 J. Biol. Chem. 177, 933-40 (1949); an acetate factor (pyruvate oxidation factor, 

 "protogen"), Snell, E. E. and Broquist, H. P.. Arch. Biochem. 23, 326 (1949). Other 

 bacterial factors are discussed by Snell, E. E., Ann. Rev. Microbiol. Ill, 97 (1949). 



