PYRIDOXINE 



absence of other factors, led to secondary symptoms such as scaly 

 skin, inflammation, alopecia and, occasionally, watery eyes. 



Pyridoxine hydrochloride is readily soluble in water (i g. in 4-5 

 ml.), acetone and alcohol (i g. in 90 ml.), and slightly soluble in ether 

 and chloroform. It melts at 204 to 206° C, with decomposition. It 

 gives a characteristic absorption spectrum with a single maximum at 

 292 mfi at pH. 3 and two maxima at 255 and 325 mfx at pH 7-45. 

 Harris et al.^ attributed this change in the absorption spectrum to a 

 tautomeric change of the type : 



CH2OH CH2OH 



HO.-^^CHaOH , -O^^CHaOH 



^" ^< 

 H 



CHai^ 'i CH, 



When the hydroxyl group was methylated, the single absorption band 

 at 280 m/x remained unchanged on altering the pJi. Pyridoxine is 

 optically inactive. 



Other compounds with vitamin Bg activity are described on 

 pages 312, 342-344- 



References to Section 5 



1. P. Gyorgy and R. E. Eckardt, Nature, 1939, 144, 512. 



2. S. A. Harris, T. J. Webb and K. Folkers, /. Amer. Chem. Soc, 



1940, 62, 3198. 



6. STABILITY OF VITAMIN Be 



Pyridoxine hydrochloride is a remarkably stable substance in 

 comparison with most other members of the vitamin B complex. 

 Thus, it was not destroyed on heating with 5N acid or alkali at 100° C, 

 by autoclaving in acid or alkaline solution, or by heating at 45° C 

 for 500 hours in a mixed oil preparation.^' 2 pyridoxal and pyridox- 

 amine (see page 312) are also stable to hot acid or alkali, although 

 pyridoxal suffered some decomposition on being heated in alkaline 

 solution. 2 All three substances can be autoclaved in 2N-sulphuric 

 acid without appreciable destruction occurring.^ 



Pyridoxine was rapidly destroyed on irradiation in neutral or 

 alkaline solution, although stable in acid solution.^' 2' * Pyridoxal 

 and pyridoxamine behaved similarly, except that the latter was 

 destroyed by direct sunlight in acid solution. ^ Red light was much 

 less destructive than blue or unfiltered light, and solutions kept better 

 in amber bottles than in colourless bottles.^ All three substances 



308 



