Ehrlich urobilinogen

It can be concluded from the publications of Rohde [2] and Freund and Lebach [3, 4] that it was Ehrlich who first suggested the use of 4-(dimethylamino)-benzalde-hyde in the presence of hydrochloric acid for color reactions with methylketols that was found also to apply to indole derivatives [S]. Auterhoff [6] designated a reagent for urobilinogen, consisting of a solution of 2 g 4-(dimethylamino)-benzaldehyde in 20 percent hydrochloric acid, correctly as Ehrlich s solution. Hence, it is essentially correct to refer to all reagents which contmn these components as Ehrlich s reagent. 

To measure the urobilinogen content of the urine samples, use Urobilistix strips, one for each urine sample. Dip them into the samples and remove the excess urine by tapping the strips against a clean, dry surface. Sixty seconds after wetting, compare the color of the test area of the strips to the color chart provided on the bottle. Estimate the urobilinogen content and record it in Ehrlich units. 

Ehrlich s aldehyde test can be used to confirm a diagnosis of acute intermittent porphyria. Equal volumes of urine and Ehrlich s reagent are mixed a pink colour indicates raised urinary concentration of either porphobilinogen or urobilinogen. In acute intermittent porphyria, raised porphobilinogen is present and the pink precipitate formed is insoluble in chloroform. 

The determination of urobilinogen based on the aldehyde reaction (which is non-specific for urobilinogen) was established by P. Ehrlich (1901). Excretion of urobilinogen in the urine is influenced by a number of factors. Since urobilinogenuria only occurs in relatively serious disorders of the hepatobiliary system, it is only of minor diagnostic relevance. A lack of urobilinogen in the urine in the presence of jaundice points to complete obstructive jaundice. Even after total cessation of bile production due to severe liver disease or destruction of the intestinal flora, urobilinogen may also be absent, (s. fig. 5.3) (s. tab. 5.8)... 

Qualitative screening tests in which urine is reacted directly with Ehrlich s reagent and assessed visually for the formation of the red chromogen (e.g., the Watson-Schwartz and Hoesch tests) are convenient but have been criticized for poor detection limits and interferences, even when solvent extraction has been used to separate the PBG-Ehrlich compound from the urobilinogen-Ehrfich complex. ... 

This solubility property differentiated it from urobilinogen, which reacts with the Ehrlich reagent to give a pink compound soluble in CHCI3. 

Urine and faecal urobilinogen can be quantitated by its colorimetric reaction with Ehrlich s reagent. 

A dipstick test, manufactured by Ames for the semiquantitative estimation of urobilinogen in urine. It is based on the Ehrlich reaction. 

The isolation of PBG by Westall (7) and the determination of its structure by Cookson and Rimington (77, 78) were crucial steps in the detailed description of the biosynthesis of porph3rrin. PBG (Fig. 11) was first detected by Sachs 88) in the urine of patients with acute porphyria, since the urine turned red with Ehrlich s reagent (p-dimethylaminobenzaldehyde in acid solution). This red compound was insoluble in CHClj thus differentiating it from urobilinogen. Waldenstrom (83) recognized PBG as a distinct entity. It has been also found in the liver and feces 84,85) of these patients. 

Urobilinogen, unlike urobilin, gives an immediate red colour with Ehrlich s aldehyde reagent in acid solution (p. 149 ). 

Ehrlich s Aldehyde Reagent, 2-3 per cent, p-dimethylamino benzaldehyde in alcohol or in 20 per cent. HCl. Reagent for muco-proteins, indole, indoxyl, urobilinogen, urea, allantoin and (in excess of strong acid) tryptophane and scatole. The reagent in 20 per cent. HCl is almost colourless, and is suitable for the urea and allantoin tests. 

---