II. CHEMISTRY 325 



Among the molds, the following have been recorded as flavin-producing: 

 Aspergillus niger, Aspergillus flavus, Penicillmm chrysogenum, and species 

 of Fusarium. 



For recovery of the vitamin from the fermented liquors adsorption-clu- 

 tion methods have been used. Another possibility is the precipitation of 

 reduced forms of riboflavin from nutrient media by the metabohc reducing 

 action of certain bacteria, particularly a group of generally avirulent strep- 

 tococci.^* For instance, up to 90% of the dissolved riboflavin can be ob- 

 tained as a red-orange, amorphous precipitate with Streptococcus faecalis, 

 under anaerobic conditions*" (cf. p. 314). Instead of bacterial reduction, 

 reducing chemicals have been used, for instance, sodium dithionite 

 (Xa-2S204 -21120), stannous, titanous, chromous, and vanadous salts. *^ These 

 methods make use of the fact that the various reduced forms of riboflavin 

 are much less soluble in water than the oxidized form. The solubility in 1 

 ml. of water is for riboflavin 100 to 130 y, for verdoflavin 50 y, for chloro- 

 flavin 20 7, and for leucoriboflavin approximately 8 7.*'* 



E. SPECIFICITY 



Some of the more important relations between chemical constitution 

 and biological activity will be discussed here. Details about the specificity 

 of fla\'in enzymes can be found in a later section. 



1. Growth Stimulators 



Riboflavin tetraacetate and diacetone riboflavin are active for rats, 

 probably as a result of hydrolysis in the organism ; the tetraacetate is, how- 

 ever, inactive on lactic acid bacteria. Riboflavin-5'-phosphate and flavin 

 adenine dinucleotide not only are growth-promoting in rats but both were 

 also as effective as riboflavin for growth and acid production of L. helveticum. 

 The flavinyl glucosides are inactive. 



It appears that only flavins which serve as a sole source of growth-pro- 

 moting flavin (in the absence of suboptimal amounts of riboflavin) for 

 L. casei and B. lactis acidi are capable of supporting growth in animals.*^ 

 To possess this activity, the flavin must be a ribityl derivative and be sub- 

 stituted in either the 6 or 7 position or both by a methyl group or by an ethyl 

 group in the 6 position, together with a methyl group in the 7 position. 

 0,7-Diethyl-9-(D-r-ribityl)isoalloxazine recently has been found capable 



••'G. E. Mines, Jr. (to Commercial Solvents Corp.), U. S. Pat. 2,387,023 (Oct. 16, 



1945) [C.A. 40, 428 (1946)]; G. W. McMillan (to Commercial Solvents Corp.), U. S. 



Pat. 2,367,646 (Jan. 16, 1945) [C.A. 39, 3400 (1945)]. 

 'o R. J. Ilickey, Arch. Biochem. 11, 2.59 (1946). 

 " G. PL nines, Jr. (to Commercial Solvents Corp.), U. S. Pat. 2,367,644 (Jan. 16, 



1945) [C.A. 39, 3.399 (1945)]. 

 ''*S. J. Shimizu, /. Fermentation Technol. {Japan) 28, 139 (1950) [C.A. 47, 1755 



(1953). 



