Due the protective action of melanin against UV radiation, a risk of sun light-associated carcinogenesis may be substantially diminished. Numerous investigations suggest that black race people have lower rate of skin cancer incidence, including malignant melanoma (melanoma malignum), than people having fair skin [English et al., 1998; Marks, 2000]. These racial differences are associated with the pigmentation degree, and thus with melanogenesis.

The aim of this study was to use the thermochemolysis method to investigate the structure of natural melanin pigments, isolated from the human melanoma malignum.

Isolation was performed using two different enzymatic methods, such as modified by the authors methods of Wilczek et al. [1990] and Double et al. [2000]. Isolated biopolymers have been thermally degraded in the presence of tetramethylammonium hydroxide (TMAH) and thermochemolysis products were analyzed by GC/MS.

Products of eumelanin origin, such as benzene, pyrrole, phenol, indole and their alkylic derivatives, were predominant in the pyrolitic profiles of melanins derived from melanoma malignum. No heterocyclic thermochemolysis products characteristic for pheomelanin-type units were present in the analyzed samples. Nevertheless, analysis of selected mass ions indicated the presence of sulfur-containing low molecular weight compounds (m/z 34 and m/z 60) in the studied pyrolysates.

Using thermochemolysis method it was possible not only to deduct the origin of the products obtained, but also to determine the degree of pigment contamination with proteins and lipids being integral parts of natural melanins.

References:

1. English DR., Armstrong BK., Kricker A., Winter MG., Heenam PJ., Randell PL., 1998, Demographic characteristic pigmentary and cutaneous risk factors for squamous cell carcinoma of the skin: a case control study. Int J Cancer., 76: 628-634.

2. Marks R., 2000, Epidemiology of melanoma. Clin Exp Dermatol., 25: 459- 463.

3. Wilczek A., Kondoh H., Mishima Y., 1996, Composition of mammalian eumelanins: analyses of DHICA-derived units in pigments from hair and melanoma cells. Pigment Cell Res., 9, (2): 63-67.

4. Double K.L., Zecca L., Costi P., Mauer M., Griesinger C., Ito S., Ben-Shachar D., Bringmann G., Fariello R.G., Riederer P., Gerlach M., 2000, Structural characteristics of human substantia nigra neuromelanin and synthetic dopamine melanins. J. Neurochem., 75, (6): 2583-2589.

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