Nicotinic acid values by chemical and microbiological methods; effect of hydrogen peroxide and infra-red rays on nicotinic acid.

For comparative purposes the nicotinic acid content of various products has been determined by both chemical and microbiological methods. Along with this comparative study, work has been done on treatments of the extracts and a study of the effects produced as a result of the treatment on the nicotinic acid content previously determined. A survey of the literature discloses that numerous discrepancies in values are obtained for nicotinic acid dependent on the material analyzed, the method used, and the treatment given the material prior to the determination. Not only do these values differ when the determinations are carried out by chemical and microbiological methods, but they also vary according to the products analyzed, indicating that certain types of materials are encountered that affect the determination when carried out by one method on some products that do not interfere in other procedures. The microbiological method selected for use in this work is the procedure of Barton-Wright (1) which we find possesses advantages over other microbiological procedures we have tried in this laboratory. This method differs from that of Krehl et al. (2) in the following points: (a) the casein hydrolysate is doubled in concentration, (6) the concentration of biotin is raised to 0.4 + per liter, (c) xanthine and xylose are added to the basal medium, (d) synthetic dl-tryptophane is used instead of natural Z-tryptophane to avoid possible nicotinic acid contamination, and (e) the commercially available vitamin-free casein hydrolysate, Smaco, is used instead of preparing the hydrolysate. This hydrolysate proved free of niacin and satisfactory in this work. The chemical procedures employed were the methods worked out by a group of cereal chemists under the chairmanship of Mr. Steele (3), and a modification of the Bina, Thomas, and Brown (4) procedure in which the samples were treated and run separately by that method. Aliquots of the samples prepared by the collaborative method were used for assay by the microbiological procedure. Brown, Thomas, and Bina (5) found that cereal extracts contained two types of compounds that are measured as nicotinic acid and are differentiated chemically by the fact that one is readily oxidized and loses its