p-AMINOBENZOIC ACID 485 



by long incubation, particularly with higher concentrations of nitro- 

 benzoic acid, indicating that the organism actually converts the p-nitro- 

 benzoic acid slowly to p-aminobenzoic acid. With growth, the nitro 

 compound is converted into p-aminobenzoic acid in sufficient quantity 

 that the conversion can be demonstrated by quantitative determination 

 of diazotizable amine and by the ability of the product to reverse the 

 toxicity of sulfathiazole for the organism. 44 



The activity of p-hydroxylaminobenzoic acid in preventing the toxicity 

 of sulfanilamide for Streptococcus hemolyticus approaches that of 

 p-aminobenzoic acid. 1 Although it is possible that samples of the compound 

 contain traces of p-aminobenzoic acid, such highly active substances 

 would not be expected to contain sufficient p-aminobenzoic acid as a 

 contaminant to account for the high activity. 1 The difference in activity 

 of p-nitro- and p-hydroxylaminobenzoic acids for Streptococcus hemoly- 

 ticus is interesting. 



For Staphylococcus aureus, 4-aminocyclohexanecarboxylic acid is ap- 

 proximately 77 per cent as effective as p-aminobenzoic acid in preventing 

 the toxicity of sulfanilic acid. This type of dehydrogenation in vivo also 

 occurs with nicotinic acid derivatives (p. 607). p-Aminobenzaldehyde is 

 apparently as active as p-aminobenzoic acid for Clostridium acetobuty- 

 licum. 



While the N-alkyl derivatives of p-aminobenzoic acid are almost de- 

 void of activity, 30 N-glycosido-p-aminobenzoic acids retain the activity 

 of p-aminobenzoic acid. N-D-Ribosido- and N-L-arabinosido-p-amino- 

 benzoic acid are as active as p-aminobenzoic acid for Clostridium aceto- 

 butylicum. 10 



Since p-aminobenzoylglycine as well as p-nitrobenzoylglycine is just 

 as active as p-aminobenzoic acid for Clostridium acetobutylicum, 18 the 

 cleavage of peptide groups appears to occur. However, p-aminobenzamide 

 is utilized inefficiently, if at all, by most of the organisms and inhibits 

 the functioning of p-aminobenzoic acid in some strains of Escherichia 

 coft 45 - 46 (p. 522). p-Acetamidobenzoic acid is utilized only with diffi- 

 culty by many organisms. Clostridium acetobutylicum appears to be able 

 to utilize p-benzamidobenzoic acid about one-tenth as effectively as 

 p-aminobenzoic acid, 17 but the activity for what is presumably another 

 strain of this organism is reported to be considerably less. 19 



p-Aminophenylacetic acid has been reported to be ten times as effective 

 as p-aminobenzoic acid for Clostridium acetobutylicum, 17 but other re- 

 ports indicate that the compound is only 0.002 to 0.01 per cent as effec- 

 tive as p-aminobenzoic acid as a growth factor, 18 " 20 and it is ineffective 

 in preventing the toxicity of sulfanilamide for this organism. 47 For other 



