358 RIBOFLAVIN 



V. specificity of Action 



M. K. HORWITT 



Riboflavin, riboflavin-5-phosphate/ and flavin adenine dinucleotide^ are 

 the only naturally occurring flavins which have been found to have vitamin 

 B2 activity. They are equally effective in promoting the growth of rats and 

 Lactobacillus casei. 



At this writing, the new vitamin activity of L-lyxoflavin, the 9-l-I'- 

 lyxityl sterioisomer of riboflavin, is being investigated. This compound has 

 been reported as a constituent of heart muscle,' but its significance awaits 

 confirmation.'* 



Synthetic derivatives of isoalloxazine which have been found to have 

 riboflavin activities include: 



(a) 7-Methyl-9-(D-r-ribityl)isoalloxazine^-^ 



(6) 6-Methyl-9-(D-l'-ribityl)isoalloxazine^'7'8 



(c) 6-Ethyl-7-methyl-9-(D-l'-ribityl)isoalloxazine^ 



These three compounds were approximately one-half as active as ribo- 

 flavin in growth tests on rats. Compound c was almost as active as riboflavin 

 in stimulating the growth of lactic acid bacteria,^ but compounds a and h 

 stimulated the bacterial growth only moderately. 



Among the synthetic arabityl derivatives which have been studied are: 



(d) 6 , 7-Dimethyl-9-(D-l'-arabityl)isoalloxazine^° 



(e) 6 , 7-Dimethyl-9-(L-l'-arabityl)isoalloxazine^^ 

 (/) 6-Methyl-9-(L-l'-arabityl)isoalloxazine8 



{g) 6 , 7-Trimethylene-9-(L-l'-arabityl)isoalloxazine^ 



Qi) 6 , 7-Tetramethylene-9- (l- 1 '-arabityl)isoalloxazine^ 



1 P. Gyorgy, Proc. Soc. Expil. Biol. Med. 35, 207 (1936). 



2 PI. P. Sarett, /. Biol. Chem. 162, 87 (1946). 



3 E. Sodi Pallares and H. Martinez Garza, Arch. Biochem. 22, 63 (1949). 

 " T. S. Gardner, E. Wenis, and J. Lee, Arch. Biochem. 34, 98 (1951). 



B P. Karrer and T. H. Quibell, Helv. Chim. Acta 19, 1034 (1936). 



8 P. Karrer, H. von Euler, M. Malmberg, and K. Schopp, Svensk. Kem. Tidskr. 47, 



153 (1935). 

 ' P. Karrer and F. M. Strong, Helv. Chim. Acta 18, 1343 (1935). 



8 R. Kuhn, H. Vetter, and H. W. Rzeppa, Ber. 70, 1302 (1937). 



9 E. E.Snell and F. M. Strong, Enzymologia 6, 186 (1939). 



i» H. von Euler, P. Karrer, and M. Malmberg, Helv. Chim. Acta 18, 1336 (1935). 

 " P. Karrer, H. Salomon, K. Schopp, F. Benz, and B. Becker, Helv. Chim. Acta 18, 

 908 (1935). 



