A novel LC-MS/MS method to quantify eumelanin and pheomelanin and their relation to UVR sensitivity - A study on human skin biopsies

Melanin in the skin can be divided into eumelanin and pheomelanin subtypes. Simultaneous quantification of these subtypes could clarify their relation to skin type and skin cancer development. We describe a novel, sensitive liquid chromatography-tandem mass spectrometry method to quantify two eumelanin markers, pyrrole-2,3,5-tricarboxylic acid (PTCA) and pyrrole-2,3-dicarboxylic acid (PDCA), and two pheomelanin markers, thiazole-4,5-dicarboxylic acid (TDCA) and thiazole-2,4,5 tricarboxylic acid (TTCA), performed in a single run using the same biopsy. Volunteers with either Fitzpatrick skin type (FST) I/II or III/IV (n = 30) each provided a 4-mm punch biopsy from the buttock. Upon analysis, the FST I + II group had significantly less of all four melanin biomarkers (PTCA, 0.75 ng/mm2 ; PDCA, 0.08 ng/mm2 ; TTCA, 0.24 ng/mm2 ; and TDCA, 0.10 ng/mm2 ) versus the FST III + IV group (PTCA, 4.89 ng/mm2 ; PDCA, 0.22 ng/mm2 ; TTCA, 2.61 ng/mm2 ; and TDCA, 0.72 ng/mm2 ), p ≤ 0.003. We find that this new LC-MS/MS method is sensitive enough to quantify eumelanin and pheomelanin markers even in the lightest skin types.