11. CHEMISTRY 



309 



ill tlic presence of riboflavin irradiation causes destruction of tryptophan 

 and i)yi-ido\in('.''""' 



Riboflavin is pnu-licafly non-toxic. Tliu toxicity to mice by intrai)erito- 

 neal injection amounts to 340 mg. per kilogram.''® The LDso value for rats, 

 using the same form of application, is oOO mg. per kilogram." The adminis- 

 tration of 10 g. per kilogram orally to rats or 2 g. per kilogram orally to 

 dogs showed no toxic effects."" 



C. CONSTITUTION 



OH OH OH 



H3C 



H3C 



o 



6,7-Dimethyl-9-(D-r-ribityl)isoalloxazine 



The side chain of riboflavin is characterized by the following reactions: 

 Acetjdation with acetic anhydride in pyridine gives a chloroform-soluble 

 tetraacetate, melting at 242 to 243°. It is easily saponified by diluted alkali 

 at room temperature; its vitamin B2 activity for rats is almost the same as 

 that of riboflavin. The formation of a tetraacetate indicates the presence 

 of four hydroxyl groups. 



Formation of a diacetone compound indicates that two hydroxyl groups 

 in pairs are adjacent. Oxidation of riboflavin with lead tetraacetate yields 

 0.8 mole of formaldehyde. That proves the presence of a primary hydroxyl 

 group in the a position to a secondary hydroxyl group. 



The oxygen-containing part of the side chain of riboflavin can be removed 

 by irradiation in alkaline solution. The resulting lumiflavin (m.p. 330°), 

 in contrast to riboflavin, is chloroform-soluble.^^*- *'• ^^ Irradiation of ribo- 



"cM. N. Meisel and E. M. Dikanskaya, Dokladi/ Akad. Nauk S.S.S.K. 85, 1377 



(1952) [C.^. 47, 2258 (1953)]. 

 36 R. Kuhn and P. Boulanger, Z. physiol. Chem. 241, 233 (1936). 

 " K. Unna and J. G. Greslin, .7. Pharmacol. 76, 75 (1942). 

 "» V. Demole, Z. Viiaminforsch. 7, 138 (1938). 

 38 O. War})urK and W. Christian, Natunvissenschafien 20, 980 (1932) ; Biochem. Z. 266, 



377 (1933). 



