Microanalysis of melanins in mammalian hair by alkaline hydrogen peroxide degradation: identification of a new structural marker of pheomelanins.
A highly sensitive, easy-to-perform method for melanin analysis in pigmented tissues based on alkaline hydrogen peroxide degradation has been developed and accomplishes simultaneous determination of eumelanins and pheomelanins. Pyrrole-2,3,5- tricarboxylic acid, the typical eumelanin marker, was obtained in higher yields than in previous procedures. A benzothiazole acid, 6-(2-amino-2-carboxyethyl)-2-carboxy-4-hydroxybenzothiazole, characterized in our previous studies as a specific marker of pheomelanins, and the newly identified 1,3-thiazole-2,4, 5-tricarboxylic acid were also used for pigment analysis. Optimal yields of the pigment markers were obtained at 24 h reaction time. Pyrrole-2,3,5-tricarboxylic acid, 6-(2-amino-2-carboxyethyl)-2-carboxy-4-hydroxybenzothiazole, and 1, 3-thiazole-2,4,5- tricarboxylic acid were quantified in a single chromatographic analysis without fractionation or work up of the degradation mixture. The linearity (linearity coefficient from 0.997 to 0.999) was excellent and the inter-assay (percentage coefficient of variation values in the range 0.2-2, n = 6) and intra-assay (percentage coefficient of variation values </= 0.4) reproducibility of the method was very satisfactory. A variety of mammalian hairs including coat color mutant mice and human hairs were used to evaluate the method. All the phenotypically pheomelanic hairs gave 1, 3-thiazole-2,4,5-tricarboxylic acid in variable yields, whereas 6-(2-amino-2-carboxyethyl)-2-carboxy-4-hydroxybenzothiazole was obtained only from some of the red hair samples examined. Notably, a marked tendency to actinic damage, as evidenced by determination of the minimal erythema dose, was exhibited by those subjects whose hair afforded the highest 6-(2-amino-2-carboxyethyl)-2-carboxy-4-hydroxybenzothiazole yields. This suggests that 6-(2-amino-2-carboxyethyl)-2-carboxy-4-hydroxybenzothiazole represents a new biogenetic marker for predicting individuals at high risk for skin cancer and melanoma.
Napolitano
A
A
Department of Organic and Biological Chemistry, University of Naples "Federico II", Italy.
Vincensi
M R
MR
Di Donato
P
P
Monfrecola
G
G
Prota
G
G
D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D006197:Hair / Q000737:chemistry; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008543:Melanins / Q000032:analysis*; D051379:Mice; D008832:Microchemistry / Q000379:methods; D011758:Pyrroles / Q000302:isolation & purification / Q000378:metabolism
D015415:Biomarkers; D008543:Melanins; D011758:Pyrroles; C018362:pheomelanin; C071226:pyrrole-2,3,5-tricarboxylic acid; D006861:Hydrogen Peroxide