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The Late Stages of Melanogenesis: Exploring the Chemical Facets and the Application Opportunities

1
Department of Chemical Sciences, University of Naples “Federico II”, I-80126 Naples, Italy
2
Hair Care Products Research Laboratories, Kao Corporation, Tokyo 131-8501, Japan
*
Authors to whom correspondence should be addressed.
Int. J. Mol. Sci. 2018, 19(6), 1753; https://doi.org/10.3390/ijms19061753
Received: 21 May 2018 / Revised: 8 June 2018 / Accepted: 8 June 2018 / Published: 13 June 2018
(This article belongs to the Special Issue Melanins and Melanogenesis: From Nature to Applications)
In the last decade, the late stages of melanin biosynthesis involving the oxidative polymerization of 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) have been extensively investigated. Most of the information derived from a biomimetic approach in which the oxidation of melanogenic indoles was carried out under conditions mimicking those occurring in the biological environment. Characterization of the early oligomers allowed for drawing a structural picture of DHI and DHICA melanins, providing also an interpretative basis for the different properties exhibited by these pigments, e.g., the chromophore and the antioxidant ability. The improved knowledge has opened new perspectives toward the exploitation of the unique chemistry of melanins and its precursors in cosmetic and health care applications. A noticeable example is the development of an innovative hair dyeing system that is based on the marked ease of DHI to give rise to black melanin on air oxidation under slightly alkaline conditions. The advantage of this method for a step-wise coverage of gray hair with a natural shade pigmentation on repeated treatment with a DHI-based formulation with respect to traditional dyes is presented. A variant of DHICA melanin combining solubility in water-miscible organic solvents, an intense chromophore in the UltraViolet-A UV-A region, and a marked antioxidant potency was evaluated as an ingredient for cosmetic formulations. View Full-Text
Keywords: melanins; chromophore; antioxidant; 5,6-dihydroxyindoles; hair dyeing; cosmetic formulations melanins; chromophore; antioxidant; 5,6-dihydroxyindoles; hair dyeing; cosmetic formulations
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Panzella, L.; Ebato, A.; Napolitano, A.; Koike, K. The Late Stages of Melanogenesis: Exploring the Chemical Facets and the Application Opportunities. Int. J. Mol. Sci. 2018, 19, 1753.

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