310 



RIBOFLAVIN 



flavin in neutral or acid solution removes the entire side chain, yielding 

 lumichrome.^'' Lumichrome is formed also by stoichiometrical oxidation of 

 riboflavin by Pseudomonas rihojiavina^^ or by mycobacteria. ^°''' Deutero- 

 flavin is a third irradiation product of riboflavin. ^^'' ^ The photochemical 

 behavior of vitamin B2 is demonstrated in the following scheme"*^: 



Riboflavin 



Ught 



acid or neutal 

 solution 



HsC 



H3C 



N 



NH 



\ 



H3C 



alkaline 

 solution 



CH3 



1 



N 



neutral solution, 

 absence of O2 



N 



\ 



CO 



NH 



/ 



N CO H3C 



Lumichrome 



\ 



N 

 Lumiflavin 



/ 

 CO 



CO T^ , Deutero- 



I alkali Deutero- 02 , 



< „ . < — ieuco- 



TVTTT ilavin „ 



NH flavin 



6,7-Dimethylalloxazine 6,7,9-Trimethylisoalloxazine 



Lumichrome is the 6,7-dimethyl derivative of alloxazine (I), whereas 

 riboflavin and lumiflavin are substitution products of the hypothetical 

 isoalloxazine (II). 



H 



CO 



NH 



In the photolysis of 9-(2'-hydroxyethyl)isoalloxazine, alloxazine is formed 



39 P. Karrer, H. Salomon, K. Schopp, E. Schlittler, and H. Fritzsche, Hclv. Chim. 

 Acta 11, 1010 (1934). 



« J. W. Foster, J. Bacterial. 47, 27 (1944); 48, 97 (1944) {C.A. 38, 1761, 5520 (1944)]. 



"" H. C. Hou, Proc. Soc. Expil. Biol. Med. 70, 581 (1949). 



" The reaction mechanism of the decomposition of riboflavin by Hghl has been dis- 

 cussed recently by R. Brdicka, Collection Czechodov. ('hem. Counnuns. 14, 130 

 (1949) [C.A. 44, 4337 (1950)]; see also ref. 42. 



