Thermochemolysis as the useful method to assess the purity of melanin isolated from the human melanoma malignum

Melanin formation in pigmented melanoma cells is considered as a target for the tumor therapy. The evaluation of potential correlation between melanin structure and the tumor type could be also of diagnostic and prognostic importance. One of the major problems in structural investigations of natural melanins is the lack of appropriate methods, which allow isolation of pure intact pigment. In this study the thermochemolysis technique was used to assess the purification grade of melanin isolated from the human melanoma malignum cells by two different enzymatic methods. Melanin samples were thermally degraded in the presence of tetramethylammonium hydroxide and the thermochemolysis products were analyzed by gas chromatography/mass spectrometry (GC/MS). Compounds of lipid origin, especially fatty acid methyl esters and aliphatic and cyclic hydrocarbons, were predominant among pyrolysis products of melanin isolated from the tumor cells by method I. In contrast, during thermochemolysis of the pigment sample isolated by the method II, mainly eumelanin markers (pyrrole and its methyl derivatives, toluene, styrene, phenol, benzyl nitrile and indole) were formed. The comparison of pyrolysis profiles of the analyzed samples indicate that method II is more efficient for melanoma pigment purification.