Dihydroxynaphthalene-Based Allomelanins: A Source of Inspiration for Innovative Technological Materials

Abstract

Melanins are a wide class of natural pigments biosynthesized by different kinds of living organisms throughout all of the life domains, from bacteria to fungi, plants, and mammals. The biological functions played by these natural pigments are different (i.e., camouflage, radioprotection, thermoregulation) and ascribable to a peculiar set of physical–chemical properties making melanins a unique class of biopolymers. Among these, allomelanins from 1,8-dihydroxynaphthalene (1,8-DHNmel) produced by some Ascomycetes have recently attracted particular interest for their robustness and ability to protect fungi against both hostile (i.e., attack from fungicidal agents) and extreme (i.e., high energy radiations) environments. Starting from this background, in this mini-review we offer a panorama of the recent advances on the oxidative chemistry of 1,8-DHN leading to the formation of allomelanin mimics with tailored structural and functional properties for technological applications.

Antioxidant Activities of Hydroxylated Naphthalenes: The Role of Aryloxyl Radicals

“…In a final series of experiments, to further address the influence of the hydroxyl groups and of their relative position on the oxidative susceptibility of the naphthalene ring, the mechanism of polymerization of the DHNs was investigated by the structural characterization of the main isolable oligomeric intermediates. To this aim, a previously reported standard protocol was adopted, involving the oxidation of the substrate by the horseradish peroxidase (HRP)/H 2 O 2 system in 0.1 M phosphate buffer at pH 7.0 [4,7] . The oligomer intermediates were isolated as the acetyl derivatives and their structures were determined by 1D/2D NMR spectroscopy and mass spectrometry (Figure 6).…”

“…To this aim, a previously reported standard protocol was adopted, involving the oxidation of the substrate by the horseradish peroxidase (HRP)/H 2 O 2 system in 0.1 M phosphate buffer at pH 7.0. [4,7] The oligomer intermediates were isolated as the acetyl derivatives and their structures were determined by 1D/2D NMR spectroscopy and mass spectrometry (Figure 6).…”

“…Most of the interest in this connection is being devoted to harnessing natural structural motifs endowed with superior hydrogen atom donor and/or electron transfer properties [2,3] . This trend is exemplified by the growing number of studies on 1,8‐dihydroxynaphthalene (1,8‐DHN) [4–9] and polymeric materials thereof. 1,8‐DHN is a naturally occurring polyketide derivative involved in the biosynthesis of black allomelanin pigments in various fungi, [10,11] such as Aspergillus fumigatus and Cladosporium sphaerospermum .…”

Melanin: insights into structure, analysis, and biological activities for future development

“…[6][7][8][9][10] Despite the progress made in recent years, the structure of melanin remains a complex and intriguing area of research. [11][12][13][14][15] This comprehensive review article aims to delve into the intricate world of melanin, with a specific focus on eumelanin and its functional structure. We will provide an in-depth exploration of the different types of melanin, their unique properties, and their critical role in biological processes.…”

The interplay of chemical structure, physical properties, and structural design as a tool to modulate the properties of melanins within mesopores

“…DHN is a metabolite and the monomer precursor of the nitrogen-free allomelanin pigment found in some fungi (i.e. Ascomyces) 55 that recently has gained particular interest not only for its biological function but also for a series of chemical and physical properties allowing for its application in different sectors 56 , 57 . As summarized in Fig.…”