Anti-Tubercular Activity of Oxidation Products of Substituted o-Phenylene Diamines

Abstract

AS reported in an earlier communication in Nature, we have been examining the anti-tubercular properties of substituted diphenyl ethers and related compounds¹. In extending this study to include diphenylamine derivatives, a curious phenomenon was encountered with 2-aminodiphenylamine. When freshly prepared, an aqueous solution of the hydrochloride of this base completely inhibits the growth of Myco. smegmatis at a dilution of 1/100,000. On keeping, and occasional warming, the inhibitory power of this solution increases gradually, the five weeks old solution producing complete inhibition at a dilution of 1/1,000,000. At the same time it was noticed that the colour of the solution rapidly changed from an initial pink to a very dark red. The highly coloured product formed in the solution was obviously of great interest. It was afterwards found that addition of ferric chloride solution to an acid solution of the base produced an immediate deep red coloration and separation of a dark crystalline precipitate. This proved to be the hydrochloride of a base, C₂₄H₁₈N₄, from which the base itself Was liberated by ammonia in the form of a brick-red crystalline powder.