II. CHEMISTRY 389 



II. Chemistry 



H. J. ALMQUIST 



There had appeared, prior to 1935, several reports of modifications of 

 the diet^"^ which had led to hemorrhagic symptoms or changes in the blood- 

 clotting power of the chicken. Although these reports may now be inter- 

 preted in terms of vitamin K, they did not contain sufficient information 

 which would clearly link the condition with a lack of a new vitamin-like 

 factor, as distinguished from possible deficiency effects of known dietary 

 requisites, or toxic substances, impaired absorption, etc. 



In 1935, papers by Dam*- ^ and by Almquist and Stokstad^"- ^^ furnished 

 the first strong chemical evidence of a new vitamin which was shown to be 

 in the fat-soluble, non-saponifiable, non-sterol fraction. It was also shown 

 that the vitamin was formed in certain feedstuffs otherwise relatively free of 

 it if these were subjected to the action of microorganisms. Sch0nheyderi2 , 13 

 made studies of blood composition in this deficiency disease and found a 

 specific lowering of the prothrombin fraction, but no other abnormalities. 

 This evidence, collectively, was sufficient to permit recognition of a new 

 vitamin, distinct from the known fat-soluble vitamins. 



A. ISOLATION 



Green leafy material was found to be a relatively rich source of the vita- 

 min. The good heat stability of the vitamin^" made possible the use of 

 commercially dehydrated alfalfa meal as a starting source for isolation 

 studies. 



Extraction of the vitamin was carried out by means of a solvent such as 

 ethyl ether, petroleum ether, or hexane. It was soon found that the vita- 

 min was too labile during alkaline saponification to permit use of this step 

 for the removal of green pigments and fats.^*' ^^ Chlorophyll and similar 



1 H. Dam, Biochem. Z. 215, 475 (1929). 



2 H. Dam, Nature 133, 909 (1934). 



3 H. Dam and F. Sch0nheyder, Biochem. J. 28, 1355 (1934). 

 ^ W. F. Hoist and E. R. Halbrook, Science 11, 354 (1933). 



6 A. A. Horvath, Am. J. Physiol. 94, 65 (1930). 



6 W. D. McFarlane, W. R. Graham, Jr., and G. E. Hall, /. Nutrition 4, 331 (1931). 



'W. D. McFarlane, W. R. Graham, Jr., and F. Richardson, Biochem. J. 25, 358 



(1931). 

 » H. Dam, Nature 135, 652 (1935). 

 9 H. Dam, Biochem. J. 29, 1273 (1935). 



10 H. J. Almquist and E. L. R. Stokstad, Nature 136, 31 (1935). 

 " H. J. Almquist and E. L. R. Stokstad, /. Biol. Chem. Ill, 105 (1935). 

 »2 F. Sch0nheyder, Nature 135, 653 (1935). 

 " F. Sch0nheyder, Biochem. J. 30, 890 (1936). 

 1* H. J. Almquist, J. Biol. Chem. 114, 241 (1936). 



