THE VITAMIN B e GROUP 659 



gensis, Streptococcus faccalis and Lactobacillus casei. For a strain of 

 Neurospora sitophila, the activities were for several of the compounds 

 between 0.1 and 1 per cent that of pyridoxal hydrochloride. For the rat, 

 definite but limited activity has been noted for some of the pyridoxal- 

 amino acids. 



After pyridoxylamino acids are autoclaved in dilute aqueous solution, 

 the resulting solution possesses high activity. 63 Since the liberation of 

 active substances could be prevented by antioxidants, such as ascorbic 

 acid, cysteine or the complete basal medium, it was proposed that an 

 oxidative and hydrolytic cleavage — presumably by intermediate for- 

 mation of Schiff bases — occurred, with the formation of pyridoxal and 

 pyridoxamine. This is substantiated by the fact that pyridoxylideneani- 

 line and other Schiff bases tested were found to be as active as pyridoxal. 

 The thiazolidinecarboxylic acid formed from L-cysteine and pyridoxal 

 [2-(2-methyl-3-hydroxy-5-hydroxymethyl-4-pyridyl) -4 -thiazolidinecar- 

 boxylic acid] was also as active as pyridoxal for all organisms. The 

 activity is attributed to pyridoxal formed by cleavage of the product 

 in aqueous solutions, since the products of cysteine with other aldehydes 

 act similarly. 03 



Pyridoxyl-/?-alanine and the condensation product formed between 

 histidine and pyridoxal [4- (2-methyl-3-hydroxyl-5-hydroxymethyl-4- 

 pyridyl)-l-imidazo(c)tetrahydropyridine-6-carboxylic acid] were in- 

 active. 63 



No significant antivitamin effect was noted for any of the pyridoxyl 

 or pyridoxylidene compounds tested. 63 



By condensation of a number of amines, including some pressor amines, 

 with pyridoxal and reduction of the pyridoxylidene derivative, a number 

 of pyridoxyl amines have been prepared. These include pyridoxyltrypta- 

 mine, pyridoxyl-/?-phenylethylamine, pyridoxyltyramine and pyridoxyl- 

 benzylamine, which have activities between 50 and 100 per cent that 

 of pyridoxine for rats. These compounds are considerably more effective 

 than the corresponding pyridoxylamino acid in replacing the vitamin B G 



Inhibitory Analogues of the Vitamin B 6 Group 



Demonstration of a growth inhibition prevented by pyridoxine was 

 first reported by Robbins and Ma, 23 who showed that the toxicity of 

 certain pyridoxine analogues for Ceratostomella ulmi was prevented by 

 sufficient pyridoxine. These analogues were 2-ethyl-3-hydroxy-4,5-bis- 

 (hydroxymethyl) pyridine, 2-methyl-3-amino-4-hydroxymethyl-5-amino- 

 methylpyridine, 2-methyl-3-amino-4-ethoxymethyl-5-aminomethylpyri- 

 dine, and 2,4,5-trimethyl-3-hydroxypyridine. Robbins 24 previously 



