IX. OCCURRENCE IN FOODS 255 



l)yrido\inc.''- In {)l:uit tissues, however, till three forms of the vitamin oicui- 

 in similar amounts. The sij^nilicancc of this (liiTcicncc in disl rihulion is nut 

 vet known. 



VIII. Standardization of Activity 



HENRY SHERMAN 



When vitamin Be was first discoxorcd it was defined as "that part of the 

 vitamin B complex that is responsil)le for the ( lire of the .specihc dermatitis 

 developed by young rats on a \itamin B-fi-ee diet supplemented with puri- 

 fied thiamine and lactoflavin."^ - The standardization of materials possess- 

 ing \'itamin Be activity was based upon the curative effect they possessed 

 against this specific dermatitis or rat acrodynia. Gyorgy^ defined the pro- 

 visional unit for the estimation of \'itamin Be or the "rat-day dose" as 

 "the minimum quantity of the substance that would cause healing of the 

 specific dermatitis." The earlier concentrates possessing vitamin Be activity 

 were adsorbates or eluates prepared from yeast or bran extracts. One milli- 

 Hter of a so-called Peters' eluate' possessed one "rat-day dose" of \'ita- 

 min Be . 



When pyridoxine was isolated as the actixe principle and was s^'nthe- 

 sized, it became the reference standard; the pyridoxine content of natural 

 materials, as measured by biological assay, was expressed in equivalent 

 amounts of the compound. One "rat-day dose" of vitamin Be became 

 equivalent to approximately 10 7 of pyridoxine. Pyridoxine is available 

 commercially as the hj^drochloride; it is a white crystalline powder which 

 is remarkably stable. A U.S. P. reference standard of pyridoxine hydro- 

 chloride is available for all assay procedures, chemical, phj'^sical, micro- 

 biological, and biological. 



IX. Occurrence in Foods 



ESMOND E. SXELL an<t CHARLES S. KEEVII., .JR. 



Most analytical figures for the vitamin Be ( ontent of foods are not satis- 

 factory, primarily because (1) several forms of the vitamin occur naturally 



1 P. Gyorgy, Nature 133, 498 (1934). 

 = T. W. Birch and P. Gyorgy, Biochem. J. 30, 304 (1936). 

 ' P. Gyorgy, Proc. Soc. Exptl. Rial. Mel. 35, 204 (1936). 



* H. W. Kiunersley, J. 1{. O'liriori, H. A. I'elers, luid V. Header, Biochem. ./. 27, 

 225 (1933). 



