Taddeini, L. published the artcileInhibition of the Ehrlich reaction of porphobilinogen by indican and related compounds, Safety of Potassium 1H-indol-3-yl sulfate, the publication is Clinica Chimica Acta (1962), 890-1, database is CAplus and MEDLINE.
From a study of the Ehrlich reaction of porphobilinogen (I) and related compounds, it was found that K indoxylsulfate (urinary indican) as well as certain other members of the indole series are markedly inhibitory. Because of the importance of this finding for detection of I in the urine, a study on the inhibitory effect of indican was made. The results revealed an inhibitory effect of indican on the I aldehyde color intensity, increasing from about 35% at a concentration of indican of 0.625 × 10-4 millimole/ml. to over 85% at a concentration of 2.50 × 10-4. Complete inhibition of the I aldehyde color reaction was obtained with an indican concentration of 5.00 × 10-4. Indole and 5-hydroxyindoleacetic acid (II) are also inhibitory to about the same degree as indican. The inhibition was not due to complexing of indoles with I since the addition of the indole to the fully developed solution of the I-aldehyde compound also produced rapid fading of the color. The mechanism responsible for the inhibition is the nucleophilic addition of indoles to the I-aldehyde compound This yields a colorless intermediary, p-dimethylaminophenylpyrrylindolylmethane. Indican inhibits the Ehrlich reaction of opsopyrroledicarboxylic acid (III) to a lesser extent (35% as compared with 86% in a 2:1 molar ratio), and II has essentially no inhibitory effect under the same conditions. III is structurally similar to I except in lacking the α-aminomethyl group of the latter compound The much smaller inhibition of III thus suggests that the α-aminomethyl group (which is protonated in the presence of the Ehrlich reagent), activated the I-aldehyde compound with respect to nucleophilic attack of the indole. However, indole itself inhibits the aldehyde reaction of III to at least 95%, in a 2:1 molar ratio. Thus, it is evident that the character of the substituents of the indole is also a factor of importance. The present observations on the inhibition of the I-Ehrlich reaction by indican and other indolic compounds clarify the recent finding that an unknown inhibitor is present in some I-containing urines responsible for false neg. Ehrlich reactions.
Clinica Chimica Acta published new progress about 2642-37-7. 2642-37-7 belongs to indole-building-block, auxiliary class Indole,Salt,Sulfonate,Inhibitor,Inhibitor, name is Potassium 1H-indol-3-yl sulfate, and the molecular formula is C7H5ClN2S, Safety of Potassium 1H-indol-3-yl sulfate.
Referemce:
https://www.nature.com/articles/s41429-020-0333-2,
Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles