Quantitative analysis of eumelanin and pheomelanin in hair and melanomas

Abstract

In this study, a method is provided for analyzing quantitatively the content and the class of melanin pigments in the tissues, e.g., hair and melanoma. The method is simple and rapid because it does not require the isolation of melanins from the tissues. The rationale was that permanganate oxidation of eumelanin yields pyrrole-2,3,5-tricarboxylic acid (PTCA) as its major pyrrolic product, which may serve as a quantitatively significant indicator of eumelanin, while hydriodic acid hydrolysis of pheomelanin yields amino-hydroxyphenylalanine (AHP) as a specific indicator of pheomelanin. The degradation products, PTCA and AHP, were determined by high-performance liquid chromatography. Sepia melanosome-melanin and synthetic 5-S-cysteinyldopa-melanin served as reference standards of eumelanin and pheomelanin, respectively. Our method provided data that corresponded well to the content and class of melanins in normal hair. Based on this control study, it was found that the melanins in the melanosomes of both B16 and Harding-Passey (HP) melanomas were eumelanic and that the melanin content in B16 melanosomes was more than 10 times higher than that in HP melanosomes, though these two melanosomes revealed distinct colors and ultrastructures, i.e., brown-black, eumelanosome-like granules in B16 and reddish- or light-brown, pheomelanosome-like granules in HP.