Product in indole detection by Ehrlich’s reagent

A review of chemical ‘spot’ tests: A presumptive illicit drug identification technique

“…Ehrlich's reagent has been used for over 100 years for detection of indoles, specifically those present in lysergic acid (LSD) and other ergot alkaloids. Kovar described the 2:1 ratio of indole to p ‐dimethylaminobenzaldehyde (p‐DMAB) in the final colored product (Figure f); however, Lamb et al determined the reaction takes place at the beta position of the indole.…”

A 3D-printed Microfluidic System for Automated and Near Real-time Quantitation of Biofilm-induced indole

“…Kovac's reagent has been used to detect indole in bacterial cultures. The functional molecule of the assay, p-dimethylaminobenzaldehyde (DMAB) can react with indole at 1:1 stoichiometry to produce a pink azoic product [29] . However, the classic Kovac's reagent (5% DMAB in 3/1 amyl alcohol/concentrated HCl; w/v) is mainly applied to answer if or not indole exists [30] , and we found that this recipe is not optimal for indole quantitation: 1) the amyl alcohol in the solvent is only slightly soluble in an aqueous solution, limiting the mixing of DMAB and the indole to be measured; 2) the 5% concentration of DMAB is low for sensitive detection.…”

Bis-indolylation of aldehydes and ketones using silica-supported FeCl3: molecular docking studies of bisindoles by targeting SARS-CoV-2 main protease binding sites

“…23 The acid-catalyzed reaction of electron-rich heterocyclic compounds such as indoles and pyrroles with p-dimethyl aminobenzaldehyde is known as the Ehrlich test. 24 Generally, 3,3 0bis(indolyl)methanes are synthesized by an analogous reaction to the Ehrlich test, where indole reacts with aldehydes or ketones in the presence of an acid catalyst to produce an azafulvenium salt, which undergoes further addition reaction with a second indole molecule to produce bis(indolyl)methanes. The role of protic acid or Lewis acid is basically activation of carbonyl and the formation of azafuvenium ions.…”