THE VITAMIN B* GROUP 657 



animal origin where pyridoxal and pyridoxamine predominate. 55 Pyri- 

 doxine occurs in as large or larger amounts than pyridoxal and pyri- 

 doxamine in plants. 55 



Yeast and molds utilized pyridoxine very effectively and in some 

 instances more effectively than either pyridoxal or pyridoxamine. 



For the few organisms tested, with the exception of the two requiring 

 the phosphorylated form of the vitamin, pyridoxal phosphate is only 3 

 to 10 per cent as effective as pyridoxal, but pyridoxamine phosphate under 

 certain conditions is more active than any other member of the vitamin 

 B 6 group for Streptococcus faecalis R. 



Pyridoxic Acid. A metabolite of pyridoxine occurring in human urine 56 

 has been isolated, identified as 2-methyl-3-hydroxy-4-carboxy-5-hydroxy- 

 methylpyridine, synthesized and given the trivial name pyridoxic acid by 

 Huff and Perlzweig. 57 - 5S 



COOH 



HO— i^S-CHjOH 



ch 3 4v 



pyridoxic acid 



Pyridoxic acid is the chief metabolic product of either pyridoxine, 

 pyridoxal or pyridoxamine. 59 Oral administration of pyridoxal to human 

 subjects results in excretion of significantly higher amounts of pyridoxic 

 acid than does administration of pyridoxine or pyridoxamine. After ad- 

 ministration of pyridoxamine, almost equivalent amounts of pyridoxal 

 and pyridoxamine are excreted; but when pyridoxal or pyridoxine is 

 ingested, the form fed is the chief form of the vitamin in the urine. 

 Although injection of pyridoxine increased the pyridoxamine and pyri- 

 doxal content of the urine, no evidence could be obtained for the conver- 

 sion of either pyridoxal or pyridoxamine to pyridoxine. The recoveries in 

 these four forms from ingested pyridoxal, pyridoxine or pyridoxamine 

 were 70, 45 and 31 per cent, respectively. 



It is interesting to note that pyridoxic acid is inactive in replacing the 

 vitamin B 6 group in the nutrition of dogs, 44 Streptococcus faecalis R, 31 

 Lactobacillus casei, 31 and Saccharomyces carlsbergensis. 31 



Both the lactone of pyridoxic acid and the lactone of 2-methyl-3- 

 hydroxy-4-hydroxymethyl-5-carboxypyridine have been reported to en- 

 hance the effect of pteroyldi-y-glutamylglutamic acid in promoting growth 

 and preventing anemia in chicks on a purified diet containing adequate 

 amounts of pyridoxine (p. 570) . 60, 61 Attempts to confirm these effects 

 have been unsuccessful. 61 * 1 The substances, designated as fi- and a-pyracin, 

 respectively, have been reported not to have any appreciable vitamin B 6 



