NICOTINIC ACID (NIACIN) 



materials yielded nicotinic acid quantitatively on digestion with taka- 

 diastase or papain. Whereas meat and milk gave the same values 

 whether an enzyme, acid or alkali was used for hydrolysis, cereals 

 gave highei results after treatment with acid or alkali than after 

 enzymic digestion. Hale et al.^^ recommended extraction of the 

 material with water at ioo° C. for forty-five minutes and subsequent 

 hydrolysis with sodium hydroxide solution in the case of seeds and 

 roots or with hydrochloric acid in the case of substances containing 

 chlorophyll ; interfering substances were then precipitated with 

 alcohol. 



Several workers have used adsorption to remove interfering 

 pigments. This does not always give satisfactory results, however, 

 as nicotinic acid and nicotinamide are readily adsorbed by some 

 adsorbents. K. V. Giri and B. Naganna ^'^ followed an initial extrac- 

 tion and hydrolysis by adsorption on charcoal at pH 6-o to 6*5, and 

 elution with 0-2 N alcoholic sodium hydroxide, and claimed to have 

 obtained satisfactory assays of foodstuffs by this method. Other 

 workers, however, obtained erroneous results. Thus, W. J. Dann and 

 P. Handler ^'^ found that the use of charcoal for decolorisation resulted 

 in large losses of nicotinic acid, and that it was impossible to com- 

 pensate for the presence of the interfering substances in coloured 

 extracts by an extrapolation method. They recommended adsorp- 

 tion of the nicotinic acid on fuller's earth, followed by elution with 

 sodium hydroxide solution, precipitation of impurities by addition of 

 lead nitrate and removal of excess lead from the filtrate by means of 

 phosphate. This gave much lower results with some biological 

 materials than did earlier methods. Corn meal, for instance, gave a 

 value of 0-6 to I mg. per loo g. compared with the value of 107 mg. 

 per 100 g. reported earlier by Waisman and Elvehjem. The method 

 gave quantitative recoveries of nicotinic acid added to liver tissues. 



K. Taufel and F. Dahle ^^ confirmed Dann and Handler's results, 

 using a variety of fuller's earth known as " Clarit Standard A " to 

 adsorb both the colour and the nicotinic acid ; the nicotinic acid was 

 then eluted from the adsorbate by means of barium hydroxide solu- 

 tion. As an alternative procedure they recommended evaporation of 

 the original solution to dryness and extraction of the residue with 

 benzene or a mixture of chloroform and isopropanol. 



Y. L. Wang and E. Kodicek ^^ eliminated interfering pigments in 

 urine by treatment with permanganate (see page 223), but when this 

 method was applied to cereals and cereal products, ^^ the values 

 obtained averaged only 75 % of those obtained by the microbiological 

 method ; the results also varied widely. More consistent results 

 were obtained by standardising the amount of permanganate by 

 keeping the temperature constant and by using Melnick's solution 



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