RIBOFLAVINE 



riboflavine. In the cockroach, the contents of the tubes were forty 

 times as rich in riboflavine as is ox-liver. 



References to Section i8 



1. G. Fraenkel and M. Blewett, Nature, 1941, 147, 716 ; 1943, 151, 

 703 ; 1943, 152, 506 ; Biochem. J., 1943, 37, 686 ; Proc. Roy. Soc. 

 B., 1944, 132, 212. 



2. L. Golberg, B. de Meillon and M. Lavoipierre, /. Exp. Biol., 



1945, 21, 84, 90. 



3. H. E. Martin and L. Hare, Biol. Bull. Woods Hole, 1942, 83, 428. 



4. E. L. Tatum, Proc. Nat. Acad. Sci., 1941, 27, 193- 



5. P. S. Sarma, Indian J. Med. Res., 1943, 31, 165. 



6. R. L. Metcalf and R. L. Fatten, /. Cell. Comp. Physiol., 1942, 19, 



373. 



7. R. G. Busnel and A. Drilhon, Compt. rend., 1943, 216, 213. 



19. ANALOGUES OF RIBOFLAVINE 



Growth Stimulators 



The first analogue of riboflavine to be prepared was 6 : 7-dimethyl- 

 9-(L-i'-arabityl)-isoalloxazine, which R. Kuhn and F. Weygand ^ 

 synthesised before it was known that riboflavine was derived from 

 ribose. It was found to possess vitamin B2 activity, though to a 

 smaller degree than the D-ribityl compound prepared subsequently. 

 Other compounds with biological activity were synthesised later, 

 mainly by Karrer and his collaborators. In general, these bore a 

 close resemblence to riboflavine and it was evident that the molecule 

 could not be greatly modified without loss of activity. Karrer et al.^ 

 found that even the L-ribityl compound, the optical isomer of ribo- 

 flavine, was inactive in rats in a dose of 20 /ng. per day. The following 

 compounds were prepared and found to be active in rats : 



6 : 7-dimethyl-9-(L-i'-arabityl)-isoalloxazine (araboflavine) ^> ^ 

 7-methyl-9-(D-i'-ribityl)-isoalloxazine 2. 4 

 6-methyl-9-(D-i'-ribityl)-isoalloxazine *» ^ 

 6-ethyl-7-methyl-9-(D-i'-ribityl)-isoalloxazine ^ 



Their activity was approximately half that of riboflavine. F. 

 Weygand ® suggested, however, that the apparent activity of arabo- 

 flavine might be due to the presence, as a contaminant, of riboflavine 

 formed by an Amadori rearrangemxCnt (see page 144). 



These analogues, with the possible exception of the arabityl 

 derivatives, were also shown to stimulate the growth of Strepto- 

 hacterium casei and B. lactis acidi.'^ 



206 



