460 NIACIN 



scribed in Section IV. LePage and Muller^^ have described a procedure for 

 obtaining TPN from hog Hver. More recently, Kornberg and Horecker" 

 have developed a method, part of which is a modification of the method 

 of Warburg and Christian, which can produce TPN of 92 % purity. TPN is 

 extracted from freshly killed sheep liver with hot water. Proteins and nu- 

 cleic acids are removed by precipitation with trichloroacetic acid. TPN is 

 precipitated from the filtrate with mercuric acetate, the salt decomposed 

 with H2S, and TPN precipitated with acetone. This product, which has a 

 purity of 8 to 13 %, is further purified by ion exchange chromatography 

 using a Dowex-1 formate column, and reprecipitation with acetone. 



B. CHEMICAL AND PHYSICAL PROPERTIES 



1. Nicotinic Acid 



Nicotinic acid is an odorless, white crystalline compound which melts 

 at 234 to 237° and sublimes without decomposition above this temperature. 

 It has a molecular weight of 123.11, and the composition C6H6O2N. It has 

 a tart taste. Table I summarizes many of the properties of nicotinic acid 

 and related compounds. 



a. Solubility 



One gram is soluble in 60 ml. of water or in 80 ml. of ethanol at 25°. It is 

 almost insoluble in ether but is freely soluble in boihng water, in boiling 

 ethanol, and in aqueous solutions of alkali hydroxides and carbonates. ^^ 

 The solubility of nicotinic acid, its hydrochloride, and its sodium salt in 

 some common solvents is shown in Table II. 



6. Stability 



Nicotinic acid is non-hygroscopic and very stable in the dry state. Solu- 

 tions may be autoclaved at 120° for 20 minutes without destruction. It is 

 stable on heating with 1 or 2 A^ mineral acid and alkali. 



" G. A. LePage and G. C. Mueller, /. Biol. Chem. 180, 775 (1949). 



" A. Kornberg and B. L. Horecker, Biochem. Preparations 2 (1952). 



"Vitamins Reviews, Niacin and Niacinamide. Merck & Co., Rahway, N. J., 1947. 



*^ N. A. Lange, Handbook of Chemistrj', 6th ed. Handbook Publishers, Sanduskj-, 



Ohio, 1946. 

 " Y. Sendju, J. Biochem. {Japan) 6, 161 (1926). 

 66 C. A. Elvehjem and L. J. Teply, Chem. Revs. 33, 185 (1943j. 

 *' P. Karrer, G. Schwarzenbach, F. Benz, and U. Solmssen, Helv. Chim. Ada 19, 826 



(1936). 

 5s O. H. Gaebler and W. T. Beher, /. Biol. Chem. 188, 343 (1951). 

 55 F. M. Strong and S. M. McElvain, /. Am. Chem. Soc. 55, 816 (1933). 

 «« L. M. Henderson, J. Biol. Chem. 178, 1005 (1949). 



