A Model Eumelanin from 5,6-Dihydroxyindole-2-Carboxybutanamide Combining Remarkable Antioxidant and Photoprotective Properties with a Favourable Solubility Profile for Dermo-Cosmetic Applications

The search for new synthetic melanin-related pigments that maintain the antioxidant and photoprotective properties of naturally occurring dark eumelanins, while overcoming their unfavorable solubility, and molecular heterogeneity is presently a very active issue for dermo-cosmetic purposes. In this...

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Bibliographic Details
Published in:International journal of molecular sciences 2023-02, Vol.24 (4), p.4241
Main Authors: Argenziano, Rita, Alfieri, Maria Laura, Gallucci, Noemi, D'Errico, Gerardino, Panzella, Lucia, Napolitano, Alessandra
Format: Article
Language:English
Subjects:
5,6 dihydroxyindole
antioxidant
Antioxidants
carboxybutanamide
Carboxylic acids
Communication
Cosmetics
Free radicals (Chemistry)
Heterogeneity
Hydrogen reduction
Intermediates
Light effects
Lipid peroxidation
Lipids
Melanin
melanins
Oxidation
photoprotection
Pigments
Solubility
Solvents
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Summary:The search for new synthetic melanin-related pigments that maintain the antioxidant and photoprotective properties of naturally occurring dark eumelanins, while overcoming their unfavorable solubility, and molecular heterogeneity is presently a very active issue for dermo-cosmetic purposes. In this work, we explored the potential of a melanin obtained from the carboxybutanamide of a major eumelanin biosynthetic precursor, 5,6-dihydroxyindole-2-carboxylic acid (DHICA), by aerobic oxidation under slightly alkaline conditions. Analysis of the pigment by EPR, ATR-FTIR and MALDI MS indicated a substantial structural similarity to DHICA melanin, while investigation of the early intermediates confirmed unchanged regiochemistry of the oxidative coupling. The pigment exhibited a UVA-visible absorption even more intense than that of DHICA melanin, and a noticeable solubility in polar solvents of dermo-cosmetic relevance. The hydrogen- and/or electron-donor ability, and the iron (III) reducing power as determined by conventional assays provided evidence for marked antioxidant properties not merely ascribable to the more favorable solubility profile, while the inhibitory action of the radical- or photosensitized solar light-induced lipid peroxidation was more marked compared to that of DHICA melanin. Overall, these results hint at this melanin, which remarkable properties are, in part, due to the electronic effects of the carboxyamide functionality as a promising functional ingredient for dermo-cosmetic formulations.
ISSN:1422-0067
1661-6596
1422-0067
DOI:10.3390/ijms24044241