VITAMIN K 



69 



their similarity. There is here apparently a competitive inhibition, the dicoumarol 

 ousting the vitamin from its place in the prothrombin formation cycle and a Vitamin 

 K deficiency is simulated. 



The administration of large doses of aspirin or salicylates sometimes produces 

 intestinal haemorrhage, possibly due to a similar antagonism, and doses of Vitamin K 

 are given to relieve the condition. 



Vitamin E, tocopherol, has a structure somewhat similar to Vitamin K and it 

 has been found that sterility caused by administration of the qui none of tocopherol 

 can be prevented by Vitamin K. 



Phthiocol from the tubercle bacillus possesses some Vitamin K activity ; and 

 both phthiocol and Vitamin K have a growth stimulating effect on Mycobacterium 

 Johnei (Johne's bacillus). The final example in this complex of interrelationships 

 and antagonisms is in relation to the purple pigment lodinin (Clemo and Mcllwain, 

 1938). This is obtained from Chrohiobacterium iodinum and is the di-N-oxide of 

 dihydroxyjihenazine, and it is therefore structurally related to pyocyanine. Its 

 structure is, however, also similar spatially to Vitamin K. lodinin inhibits the growth 

 of a number of organisms especially hsemolytic streptococci and it is found that this 

 inhibition is reversed by Vitamin K. Mcllwain's view is that iodinin is inactivated 

 by reduction by the bacteria in conjunction with the antagonising quinone ; the 

 problem is to explain why the quinones are more active in this respect than other 

 oxidation-reduction systems. 



2-Methyl-l : 4-naphtha quinone may be determined quantitively by reduction 

 to hydro quinone and titration with 2 : 6-dichlorophenol indophenol. In acid alcohol 

 containing lithium the Eq value was found to be + 0-363 using potentiometric 

 methods, whilst with the polarograph the value of + 0-328 v. was obtained (Riegel, 

 Smith and Schweitzer, 1940 ; McCawley and Gurchot, 1940 ; Trenner and Bacher, 

 1941). 



DIALURIC ACID—ALLOXAN SYSTEM 



The system dialuric acid — alloxan is a reversible oxidation-reduction system 

 (Biilmann and Bentson, 1928) : — 



O+C3H2O3N2. CHOH ^ C3H2O3N0. CO. H2O 



The reductant (dialuric acid) and oxidant (alloxan) also combine together to form 

 alloxanthine, which is analogous to a meriquinone (described in the section on 



