Urochromogen

Urochromogen is a sulfur-containing pigment of urine that appears in large quantities only in pathological cases, primarily in the presence of increased tissue breakdown. In normal urine, it is present in small quantities. It has not yet been possible to isolate it in a pure form. Like urochrome, urochromogen can be accumulated by freeing urine from red coloring substances and saturating it with ammonium sulfate. From the filtrate, urochromogen is extracted with alcohol. In an acidic medium, urochromogen is weakly colored; in a neutral or alkaline medium, it has a yellow-green color. An aqueous solution of urochromogen gives a positive Ehrlich's diazo reaction, which, as is evident, depends on the phenol derivatives included in the composition of urochromogen. Upon adding a drop of KMnO₄ to the urochromogen solution, it is oxidized into urochrome and produces an intensely yellow color, which Klemperer uses for the quantitative determination of urochrome, proposing as a comparison liquid an 'Ecmgelb' G solution calculated at 0.001 of dye per 180 cm³ of water. The degree of coloration of this solution corresponds to the coloration of 0.1% urochrome. Upon standing in air, the following precipitate out of an acidic solution of urochromogen: 1) a black precipitate—uromelanin, which is insoluble in alcohol, and 2) a ruby-red body, soluble in alcohol, which, after the addition of water, precipitates in the form of a resinous mass. The latter consists of ether-soluble omicholic acid and the insoluble pigment uropittin. By adding an alkaline lead solution to the urochromogen solution, sulfur is split off from the urochromogen. Urochromogen gives a positive xanthoprotein reaction. The Millon reaction is negative. It is necessary to note that, as is evident, urochromogen does not represent a definite chemical body, but consists of a whole series of chromogens that determine the color of urine. The question of the origin of urochromogen is controversial. A whole series of researchers is inclined to think that it is of protein origin, while others attempt to prove its hematogenous nature. Recently, an attempt has been made to identify it with a pigment obtained from hemoglobin, named by the author 'hemo-urochrome' (Nothhaas). The quantitative determination of urochromogen in urine is of significance only for judging the presence of increased protein breakdown.

I. Itsikeon.