Xanthurenic Acid and Its Role in the Tryptophane Metabolism of Pyridoxine-deficient

In a previous publication (1) the isolation of a green pigment from the urine of pyridoxine-deficient rats was described. The green pigment was shown to be the product of a reaction between ferric ammonium sulfate or other ferric salts and a compound whose nature was unknown. This compound has now been isolated in crystalline form. It is a yellow pigment and has been identified as xanthurenic acid. Isolation of Xanthurenic Acid-The xanthurenic acid was isolated from the urine of pyridoxine-deficient rats with the help of the paper-packed chromatographic column described in a previous publication (1). Cotton pulp has been used successfully and can replace the paper pulp. The yellow pigment was lightly adsorbed from rat urine’ which had been saturated with sodium chloride. The column was washed with saturated sodium chloride solution, which carried through most of the urinary constituents before the yellow pigment came through. This process was repeated until the yellow pigment was obtained in a fair degree of purity. The sodium chloride-saturated solution containing the yellow pigment was then concentrated to about one-tenth of its volume and the precipitated sodium chloride removed by filtration. At this point, two different procedures were employed. The solution was further concentrated until, along with sodium chloride, the yellow pigment crystallized out in needles which aggregated to form rosettes. The crystal form of the yellow pigment is illustrated in Fig. 1. The yellow pigment could be separated from the sodium chloride by recrystallization. The second procedure consisted of eliminating most of the salt from the solution with alcohol and acetone. 2 to 4 volumes of alcohol were added to the salt-saturated solution and to this alcoholic solution was added an equal volume of acetone. The precipitate was discarded and the filtrate was