ANEURINE (thiamine) 



buffer, whilst Myrback et al.^ showed that the pyrophosphate ion had 

 a marked stabilising effect at ^H 2 to 6-5 ; the optimal ^H for stability 

 on sterilisation was 6-5. 



K. T. H. Farrer ® subsequently showed that a linear relationship 

 existed between the reaction velocity of the destruction of aneurine 

 and the hydrogen ion concentration for any given buffer in the ^H 

 range 3 to 8. The relationship varied for each buffer, however, and 

 the slope of the curve changed as the ionic constitution of the solution 

 altered ; where this was accompanied by a large change in pH there 

 was a correspondingly large change in the slope of the curve obtained 

 by plotting _^H against the logarithm of the velocity coefficient. The 

 reaction velocity increased as the ^H rose. R. G. Booth * also showed 

 that copper (2 p. p.m.) catalysed the destruction of aneurine, whereas 

 iron, almninium, zinc and tin had no effect. According to K. T. H. 

 Farrer,'' however, the effect of copper is variable and, whilst destruc- 

 tion is more rapid in presence of copper in phosphate or phosphate- 

 phthalate solutions, the rate of destruction may actually be decreased 

 by the addition of copper to phosphate solutions containing tartrate, 

 citrate or glycine. Arising out of this work, it was noticed that 

 aneurine was destroyed more slowly in buffer solutions considerably 

 more dilute than those used in earlier experiments, and further in- 

 vestigation showed ® that in phosphate buffer the concentration of 

 buffer salts affected the rate of destruction of aneurine below pR 6 ; 

 the addition of citric acid eliminated this effect, whereas phthalate 

 enhanced it. The rate of destruction was also dependent on the 

 initial concentration of aneurine, being higher the more concentrated 

 the solution, irrespective of the nature of the buffer solution.®" 



Stabilisation of Aneurine Solutions 



F. C. Mclntire and D. V. Frost * claimed that aneurine solutions 

 could be stabilised by a- or j3-amino acids, and that the effect was 

 lost when the amino group was acetylated or the amino acid was 

 converted into a betaine, but, rather surprisingly, not when the 

 carboxyl group was converted into an amino group or when one or 

 two methyl groups were introduced into the amino group. Removal 

 of the amino group farther from the carboxyl group than the jS-position 

 gave compounds that promoted the destruction of aneurine, although 

 lysine was said to be as effective as glycine. Anthranilic acid had a 

 protective action, m-aminobenzoic acid was without effect, whilst 

 _/)-aminobenzoic acid had a destructive effect. Taurine, benzyl amine, 

 diallylamine and tri-n-butylamine were protective and all other 

 amines tested proved to be destructive. Nicotinic acid and nicotin- 

 amide were also destructive. 



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