Melanins are the major determinants of pigmentation of skin, hair and eyes in humans. These pigments originate from the tyrosinase-catalyzed oxidation of tyrosine, leading to the unstable 3,4-dihydroxyphenylalanine (DOPA) quinone that through polymerization produce a black insoluble eumelanins. Nucleophilic addition of cysteine to DOPA quinone produces alkali-soluble pheomelanins via 5-S-cysteinylDOPA (CD). This present study will provide the basis for the development of technologies to use CD-based polymers for implementation of eumelanin/polydopamine coatings. From a biological viewpoint, definition of the described processes will throw light on the mode of formation of melanosomes and melanized granules in neuromelanin and irides, unraveling a natural strategy to mask an oxidant active polymer of potential toxicity by growth of a pigment shell, which is expected to be less toxic.