Abstract
The futility in expecting to obtain an unaltered metabolic product of a complex character like human or animal melanin after prolonged boiling with caustic or concentrated mineral acids, was pointed out by Gortner 1 . The method of isolation of urinary melanin by direct precipitation of the urine either with basic lead acetate or with barium hydroxide suffers from the disadvantage that a great variety of compounds besides the melanin is taken down by either method; which fact does not facilitate the purification.
Due to the great scarcity of melanuria in cases of melanosarcoma in man, the problem of a simple and at the same time mild method for the isolation of melanin from human urine is only seldom attacked. The fact that we are engaged in the isolation of another cyclic urinary compound 2 made it possible for us to use the occasion of obtaining melanotic urine from a middle aged man with multiple metastases from a melanosarcoma of the skin. The abundance of melanin produced and circulated in the organism in this patient was demonstrated not only by the occurrence of melanin in his urine but also by a unique diffuse melanotic discoloration of the skin giving a slate colored character particularly to face and hands.
For the isolation of the melanin the following procedure has been employed: The urine is evaporated on a water bath in a current of air and the residue is extracted with absolute methyl alcohol. The extraction is carried out in a tall cylinder or beaker and the salts allowed to settle slowly. This process is repeated several times with fresh washings of methyl alcohol until the final washing is straw colored or colorless.
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