STUDIES ON THE CHEMICAL DIAGNOSIS OF PELLAGRA (NICOTINIC ACID DEFICIENCY) 1

Since the demonstration that nicotinamide is the pellagra-preventing factor (1), attempts have been made to analyze this substance in blood and urine as a measure of nicotinic acid nutrition. Chemical methods and biological methods, to be considered subsequently, have been used. The chemical methods have been based, most com-monly, upon the development of colored products by the reaction of various pyridine compounds with cyanogen bromide and aromatic amines, as described by Konig (2). This reaction is not specific for nicotinic acid.-Other pyridine compounds may give similar col-ored products. Elvehjem (3) has found that, in the analysis of animal tissues, the reaction as we have applied it gave results quite comparable to those which he obtained by animal assay. He found that, in vegetable materials, the chemical method gave too high values, presumably due to other pyridine compounds. Consequently, blood analyses might be expected to avoid the possible errors due to the concentration of those other compounds in the urine. Nicotinic acid does not occur, as such, in appre-ciable quantities in the blood or urine except shortly after the taking of large doses of it (4, 5). In the blood, it occurs chiefly in the corpuscles as a constituent of coenzymes I and II. Nicotinic acid in the blood has been determined by four different procedures: chemical estimation using the cyanogen bromide and aromatic amine reagents, measurement of coenzymes I and II as the essential growth factor for H. influenzae or H. parainfluenzae, estimation of total nicotinamide 1 The expense of this investigation was defrayed by grants from the Upjohn Company, Kalamazoo, and fro