RIBOFLAVIN 677 



week. L-Araboflavin (200 y per day), which possesses some growth- 

 promoting properties itself, appears to reduce very slightly the growth 

 of rats receiving low amounts of riboflavin (10 y per day). 22 D-Arabo- 

 flavin, at a concentration of 25 y per cc, also inhibits the growth of an 

 unidentified strain of lactic acid bacteria. 



Galactoflavin [6,7-Dimethyl-9-(D,l'-dulcityl)isoalloxazine]. The admin- 

 istration of galactoflavin (1.0 to 2.16 mg) daily by stomach tube increases 

 the mortality rate and decreases the rate of growth of rats on a ribo- 

 flavin-free diet. The analogue (2.16 mg per day) completely inhibits the 



-CH 2 OH 



O 



galactoflavin [6 ,7-dimethyl-9-{D ,1' -dulcityl)isoalloxazine\ 



response of the animals to 10 y daily of riboflavin and markedly inhibits 

 the response to 40 y daily of the vitamin. The inhibitory effect of 2.16 mg 

 of the analogue is almost, but not completely, prevented by 200 y per day 

 of riboflavin. The index at which growth inhibition is noted is approxi- 

 mately 10. 



Lumichrome and Lumiflavin. The growth of a mutant strain (51602) 

 of Neurospora which requires riboflavin when incubated at 31-34° C, but 

 not when incubated at 25° C, is inhibited by both lumichrome and lumi- 

 flavin. 53 The inhibition resulting from either compound is competitively 

 prevented by riboflavin. In tests incubated for 84 hours at 31° C, the 

 inhibition index for lumichrome was 2.2-2.5 for half-maximum and 6-8 

 for complete inhibition of growth. Lumiflavin was only about one- 

 twentieth as effective as lumichrome. 53 



CH 3 



N NH N N 



CH 3 -L^> X ^C x Jm CH 3 -l^J x A .NH 



N C N C 



H 



o 



lumichrome lumiflavin 



(6 ,7-dimethylalloxazine) (6,7,9-trimethylisoalloxaziiie) 



