Reagent, Ehrlich

Inhibition of tomato and barley plants growing in soils infested with Centaurea repens (knapweed) was reported by Fletcher and Renney (38). A toxic component was isolated in highest concentration from the foliage of knapweed. The inhibitor was considered to be an indole alkaloid or auxin precursor because of its ultraviolet absorption spectrum and the positive reactions obtained with Salkowski and Ehrlich reagents. The presence of the inhibitor was considered to explain partially the rapid establishment of Centaura spp. in almost pure stands. 

Reaction of the amine with p-dimethylaminobenzaldehyde (Ehrlich reagent) or p-diethylaminobenzaldehyde to produce a colored Schiff base [23—25]. The color formation is ascribed to a resonance hybrid between a protonated Schiff base and a quinoid system (Eq. (2)) ... 

The Ehrlich reagent will react with tryptophan and ureas to give a purple and yellow color, respectively. 

To prepare the Ehrlich reagent, solution I (10% 4-(dimethylamino)benzaldehyde in coned HC1) is first made. Just before use, solution I and acetone (1 4) are mixed in a fume hood and used as a spray. 

The ninhydrin test will not interfere with the Ehrlich reagent. Therefore, a plate can be examined under UV light, immersed in iodine vapors, treated with ninhydrin, and the Pauly or Ehrlich reagents successively. 

The quantitative assay for PBG and ALA (Bio Rad, Hercules, CA, USA) that is based on the classical method by Mauzerall and Granick may be used for determination of the porphyrin precursors. PBG is absorbed by the anion-exchange column and ALA by the cation-exchange column interferences are washed out. After elution from the column, ALA is derivatized by acetyl acetone to form a pyrrole. Both ALA and PBG are determined colorimetrically with the modified Ehrlichs reagent. Instead of this broadly used standard method ALA, but not PBG may be detected and quantified using amino acid chromatography. However, our experience has shown that this method is only valid for detecting massively increased concentrations of ALA. 

Modified Ehrlichs reagent (prepare freshly for each use, stable for 6 h only) 2 g... 

The Ehrlich reagent, developed originally for the colorimetric assay of pyrrole derivatives, was shown by Ehrlich to give a color with certain glycoproteins, with and without prior alkali treatment (3). The reagent consists of dimethylaminobenzaldehyde in strong hydrochloric acid. This assay later became the basis for the Morgan-Elson reaction for the deter-... 

The two earliest structures (14, 20) shown in Figure 3 were based on the reactivity of these compounds to the Ehrlich reagent. The pyrrole-2-carboxylic acid of the second formula was presumed to be attached to protein by the hydroxyl group at the 4-position of the pyrrole ring. 

Ehrlich reagent solutions I and II, 657 electrolyte solution (electrical pulse counting), 584-585 ethanolic potassium hydroxide solution, 0.5 M, 460... 

Ehrlich reagent Blue-violet to red-violet spots 26... 

Cobalt (II) thiocyanate Diazotization and a-naphthol coupling Ehrlich reagent Fast Blue B Salt... 

Dimethylaminocinnamaldehyde Ehrlich reagent Ferric chloride (3%) p-Nitroaniline, diazotized Sodium bisulfite, aqueous Ninhydrin... 

Iodides Cinnamaldehyde/hydrochloric acid 4-N,N- dimethylaminocinnamaldehyde Ehrlich reagent Ferric chloride (0.001 M) in 5% perchloric acid Naphthoquinone/perchloric acid Perchloric acid (5%)/ferric chloride (0.001 M) Prochazka reagent Salkowski reagent van Urk (or Stahl) reagent Xyanthydrol (0.1% in acidified ethanol) Sonnenschein test... 

Chromogens I and III were found to contain, respectively, one and two double bonds the hydrogenated derivatives gave no reaction with the Ehrlich reagent. Chromogen III was formulated as 3-acetamido-5-(l,2-dihydroxyethyl)furan (CXIX), and was found to be identical with the syn-... 

An alternative possibility is that of the condensation of two molecules of N-acetyl-glucosamine in the presence of alkali to yield a pyrazine derivative.55 This is suggested by the fact that N-acetylaminoacetalde-hyde under alkaline conditions affords N-diacetylpyrazine which gives a color with the Ehrlich reagent. 

The determination of o-aminohippuric acid was recently checked its spot is eluted with the same Ehrlich reagent and the color developed is read immediately at 470 mp (Benassi, unpublished data). 

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