PYRIDOXINE 



S.faecalis R and L. helveticus}^ whilst for other micro-organisms, such 

 as Saccharomyces carlsbergensis }'^ the three compounds were about 

 equally effective. A few micro-organisms, including Saccharomyces 

 cerevisiae ^ and pyridoxineless Neurospora sitophila,^^ did not respond 

 at all to pyridoxamine or pyridoxal. 



Rats responded equally well to pyridoxine, pyridoxal and pyri- 

 doxamine, whilst for chicks, ^^ pyridoxal and pyridoxamine had 

 three-fifths and four-fourths respectively of the activity of pyri- 

 doxine. 



The biological activity of pyridoxal phosphate for rats was equiva- 

 lent to its pyridoxal content.^* 



Heyl et al}^ found that the following derivatives of pyridoxamine 

 had 50 to 100 % of the activity of pyridoxine on rats : pyridoxyl-^- 

 phenyl ethylamine, pyridoxyl-tyramine, pyr idoxyl- try pt amine, pyri- 

 doxyl-benzylamine, pyridoxyl-histamine and pyridoxyl-isobutylamine. 

 They had little or no microbiological activity. ^^« 



Pyridoxic Acids and Lactones 



Two pyridoxic acids exist, formed by the oxidation of one or 

 other of the hydroxymethyl groups to a carboxyl group. These give 

 rise to lactones, known as pyracins (page 336) : 



CO— O CH2-O 



COOH I 1 CH2OH I I 



uo/^ 



CH5 



CH,OH > Ho/^— CH, Ho/\cOOH 



CH; 



HO 



3^ / CH3L jl CHg^ y 



1— CO 



4-Pyridoxic acid /3-Pyracin 5-Pyridoxic acid a-Pyracin 



4-Pyridoxic acid did not stimulate the growth of micro-organisms,^^ 

 but the corresponding lactone, j3-pyracin, had one-quarter the activity 

 of pyridoxine for S. lactis, i/5oth for L. helveticus and i/400oth for 

 yeast. a-Pyracin was also without appreciable growth-promoting 

 properties on yeast. ^^ According to Luckey et al.^^ a-pyracin had no 

 vitamin Bg activity in chicks, but Scott et al.^^ found that it promoted 

 growth in chicks and significantly increased the haemoglobin content 

 of the blood, as well as stimulated the growth of L. helveticus. ^-Pyra- 

 cin was more effective than a-pyracin in promoting growth, but only 

 slightly more effective in preventing anaemia. ^^ In the absence of 

 a- or jS-pyracin, but in presence of folic acid (page 485), a normocytic, 

 hypochromic anaemia developed. Another closely related substance 

 that prevented anaemia in chicks was 3-carboxy-4-hydroxymethyl- 

 6-methyl-2-pyridone : '^^ 



344 



