STANDARDS FOR THE K VITAMINS 843 



property is not displayed by naphthoquinones without a side chain on 

 position 3. 



6. Standards for the K Vitamins 



There are no national or international standards for vitamin K, and this 

 is probably unnecessary, in view of the ready availability of pure 2-methyl- 

 1,4-naphthoquinone. However, both 2-methyl-l,4-naphthoquinone*^''"' 

 and 2-methyl-l,4-naphthohydroquinone diacetate^^-^^ have been suggested 

 as possible reference standards, as their physical constants are well known 

 and they are quite stable. 



Although it is obvious that vitamin K activity can now best be expressed 

 in relation to the biological effect of a given amount of 2-methyl-l,4-naph- 

 thoquinone, it is important to understand the earlier methods of expressing 

 biological activity before the nature of the vitamin K was discovered. 

 These relationships are given in Table 2, which has been worked out by 

 Ansbacher.''^ By definition, the activity of 1 mg. of vitamin Ki is equiva- 

 lent to 1000 Thayer-Doisy (1939) Units; since 2-methyl-l,4-naphthoquin- 

 one has 3.3 times the efficacy of natural vitamin Ki, it is equivalent to 3300 

 Thayer-Doisy (1939) Units. 



TABLE 2 

 Biological Activity of Various Methods of Expression of Vitamin K Effect in 

 Terms of Activity of 2-Methyl-1,4-Naphthoquinone (Menadione) and Thayer- 

 Doisy (1939) Units 



" S. A. Thayer, S. B. Binkley, D. W. MacCorquodale, E. A. Doisy, A. D. Emmett, 

 R. A. Brown, and O. D. Bird, J. Am. Chem. Soc., 61, 1932, 2563 (1939). 



'' S. Ansbacher, J. Nutrition, 17, 303-315 (1939); /. Biol. Chem., 133, iii-iv (1940). 



•= H. R. Rosenberg, Chemistry and Physiology of the Vitamins, Interscience, New York 

 1945 p. 504. 



<< H. bamj Z. Vitaminfarsch., 8, 248-257 (1938). 



' F. P. Dann, Am. J. Physiol, 123, 48-49 (1938). 



/ F. P. Dann, Proc. Soc. Exptl Biol. Med., 4^, 663-668 (1939). 



69 S. A. Thayer, S. B. Binklev, D. W. MacCorquodale, E. A. Doisy, A. D. Emmett 

 R. A. Brown, and O. D. Bird, J. Am. Chem. Soc, 61, 2563 (1939). 



TO E. Fernholz, S. Ansbacher, and H. B. MacPhillamy, J. Am. Chem. Soc, 62, 430-432 

 (1940). 



71 H. Dam, J. Glavind, and P. Karrer, Helv. Chim. Ada, 23, 224r-233 (1940). 



" S. Ansbacher, J. BioL Chem., 133, iii-iv (1940). 



