614 THE BIOCHEMISTRY OF B VITAMINS 



amide prevented these abnormalities. 76 A beneficial effect of nicotinic 

 acid on the isolated heart had been previously observed in the absence 

 of an inhibitory analogue, 77 and in clinical studies marked alterations in 

 the electrocardiogram, which disappear promptly after nicotinic acid 

 therapy, have been noted in patients with pellagra. 78 



Other Analogues of Nicotinic Acid and Nicotinamide. 6-Aminonico- 

 tinic acid which inhibits the utilization of p-aminobenzoic acid for a 



-COOH r^N— CO— CH 2 — CO- 



NH 2 -^ N ' 



6-aminonicotinic acid dibenzoylmeihane 



{1 ,3-diphenyl-l ,3-propanedione) 



number of organisms (p. 527) prevents the growth of Staphylococcus 

 aureus in a synthetic medium at a concentration of 1 y per cc. 79 The 

 growth inhibition is reported to be prevented by either nicotinic acid or 

 nicotinamide at concentration 0.1 to 0.01 that of the inhibitor. p-Amino- 

 benzoic acid does not affect the inhibition. 79 



l,3-Diphenyl-l,3-propanedione (dibenzoylmethane) inhibits the growth 

 of Proteus vulgaris. The inhibition of growth is prevented by sufficient 

 nicotinamide. The inhibition index is reported to be approximately 100. 42a 



Thiazole-5-carboxamide exerts a slight toxic effect for Staphylococcus 

 aureus at relatively high concentrations. 53 This effect contrasts with the 

 ability of the compound to prevent the toxicity of 3-pyridinesulfonic acid 

 for Proteus vulgaris. 



2- (5'-Thiazolecarboxamido) pyridine neither inhibits nor promotes 

 growth of Staphylococcus aureus. 53 



N-2-Pyridyl-3-pyridinesulfonamide is reported to be less effective as 

 an inhibitor than the corresponding sulfonamide or sulfonic acid. 80 It has 

 been indicated (Table 23) that it replaces the requirement of Staphylo- 

 coccus aureus for nicotinic acid. 53 



The toxicities of coramine, picolinic acid, pyridine-3-sulfonic acid, 

 thionicotinamide, thiopicolinamide, quinoline-3-carboxylic acid, quinoline- 

 2-carboxylic acid (quinaldinic acid) , and N,N-diethylpyridine-3-sulfon- 

 amide were all found to be of a low order for Proteus vulgaris and 

 Streptobacterium plantarum, and were not prevented by nicotinic acid or 

 nicotinamide. The latter two were toxic themselves at a concentration 

 approaching that of some of these analogues. 65 5-Thiazolecarboxylic acid 

 was toxic for Streptobacterium plantarum only at high concentrations at 

 which its inhibitory effects were not prevented by nicotinic acid or 

 amide. 65 



