PHYSIOLOGIC ROLE OF VITAMIN K 



769 



and those which coiiuteract the effect of these agents. The activity of 

 menadione (A), which is the most potent antihemorrhagic agent, is re- 

 duced when OH is introduced into position 3 (phthio(H)l) (B); when the 

 method group is replaced b}' an ethyl radical, the antihemorrhagic activity 

 is further decreased (Compound C), while the combining of two molecules 

 of phthiocol through their methyl groups (Compound D) actually produces 

 an ti vitamin K activity.'^- Similarly, when two menadione molecules 

 are combhied, the resulthig comj^ound is no longer an antihemorrhagic 

 agent but possesses hemorrhagic properties. '^'^ The relationship of some 

 of these compounds to dicumarol is shown in Figure 1. 



CH, 



O 

 Menadione 



B. Phthiocol 



C. 2-Ethyl-3-hydroxy- 

 1,4-naphthoquinone 



OH 



D. 3,3'-Methylenebis 

 ( 4-hydrox j'cumarol ) 



E. Dicumarol 



Fig. 1. The effect of structural changes on the action of a compound as a hemorrhagic 

 agent (D, E) or as an antihemorrhagic agent (A, B, O.^-" 



Several compounds which do not occur as "double molecules" possess 

 hemorrhagic properties. Thus, in the compound shown below, the nature 

 of the R group determines its acti\'ity. If R is a halide or a phenyl deriva- 

 tive, it is an antivitamin K.'"*' If R is a methyl group, the compound has 



=0 



's- P. Mevmier and C. Mentzer, Bull. soc. chim. bioL. 25, 80-86; with N. P. Buu-Hoi 

 and P. Cagniant, 384-390 (1943). 



'" C. Mentzer, Bull. soc. chim. biol., 30, 872-884 (1948). 



