528 THE BIOCHEMISTRY OF B VITAMINS 



in mice infected with streptococci, gonococci and meningococci. The 

 compound had only a slight effect against staphylococci and pneumococci 

 in vivo. 396 Although the inhibitory activity of p,p'-diaminobenzoin against 

 Streptobacterium plantarum approached that of p,p'-diaminobenzil for 

 short periods of incubation, the benzoin derivative decreased markedly 

 in activity with increased incubation periods to only a small fraction of 

 the activity of the benzil derivative. 26 It was suggested that the organism 



■— f \-CO— CHOH— / \— NH 2 H 2 N-/ \— i 



p,p'-diaminobenzoin p-aminoacetophenone 



oxidized the benzoin derivative to p-aminobenzoic acid, thereby effecting 

 a reversal of the inhibition. p-Aminobenzophenone is about 10 to 25 per 

 cent as effective as sulfanilamide in preventing growth of Streptobac- 

 terium plantarum, and p ; p'-diaminodesoxybenzoin and p-aminobenzophe- 

 none are only slightly inhibitory to that organism. p-Nitroacetophenone 

 appears to be more effective than p-aminoacetophenone against Strepto- 

 bacterium plantarum. 



Miscellaneous Analogues. p-Nitrobenzoic acid at low concentrations 

 inhibits the growth of Streptococcus viridans, and the growth inhibition 

 is prevented by p-aminobenzoic acid; at higher concentrations the 

 nitro compound does not inhibit growth of the organism. Under these con- 

 ditions, the organism produces a diazotizable amine in the medium which 

 has anti-sulfonamide properties. 44 Consequently, it appears that reversals 

 noted at high concentrations are the result of the action of p-amino- 

 benzoic acid accumulating from reduction of the inhibitor by the organ- 

 ism. 



p-Aminobenzamide is an inhibitory analogue of p-aminobenzoic acid 

 for Escherichia coli, but is not particularly effective. Similar results have 

 been obtained with 2- (4-aminobenzamido) pyridine against Streptobac- 

 terium plantarum. 



Ethyl p-aminobenzoate is an inhibitory analogue of p-aminobenzoic 

 acid for Streptobacterium plantarum. 421 



o-Aminobenzoic acid at a very high inhibition index is toxic for Stri- 

 gomonas oncopelti 137 and m-aminobenzoic acid has some inhibitory ac- 

 tivity against Streptobacterium plantarum. 421 For the latter organism a 

 high concentration of benzoic acid is toxic, and the inhibition is prevented 

 by p-aminobenzoic acid. 421 



Even p-aminobenzyl alcohol has some ability to inhibit the utilization 

 of p-aminobenzoic acid by some organisms. 4203 6-Amino-2-naphthoic acid 

 is slightly inhibitory to Streptobacterium plantarum. 396 



