Red-Hair-Inspired Chromogenic System Based on a Proton-Switched Dehydrogenative Free-Radical Coupling

Leone, Loredana; Crescenzi, Orlando; Amorati, Riccardo; Valgimigli, Luca; Napolitano, Alessandra; Barone, Vincenzo; d’Ischia, Marco

doi:10.1021/ol402161j

Cited by 13 publications

(26 citation statements)

References 21 publications

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“…It has been suggested that the lower ionization potential of pheomelanin (i.e., the energy required to remove an electron from the molecule), favoring formation of sulfur‐stabilized radical cations, and the lower melanosomal pH of pheomelanin synthesis than eumelanin synthesis play some role in promoting ROS formation (Mitra et al., ). This suggestion, though chemically questionable due to the lack of specific evidence for sulfur‐stabilized radical cations in pheomelanins, would be consistent with the remarkable ability of the benzothiazines constituents of pheomelanins to undergo H‐atom abstraction and free‐radical dimerization upon protonation (Leone et al., ; Napolitano et al., ) (Figure ).…”

Section: The Dark Chemistry Of Pheomelanin: Prooxidant and Redox Propmentioning

confidence: 71%

Pheomelanin‐induced oxidative stress: bright and dark chemistry bridging red hair phenotype and melanoma

Napolitano

Panzella

Monfrecola

et al. 2014

Pigment Cell Melanoma Res

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Summary The complex interplay of genetic and epigenetic factors linking sun exposure to melanoma in the red hair phenotype hinges on the peculiar physical and chemical properties of pheomelanins and the underlying biosynthetic pathway, which is switched on by the effects of inactivating polymorphisms in the melanocortin 1 receptor gene. In addition to the long recognized UV‐dependent pathways of toxicity and cell damage, a UV‐independent pro‐oxidant state induced by pheomelanin within the genetically determined background of the red hair phenotype has recently been disclosed. This review provides a detailed discussion of the possible UV‐dependent and UV‐independent chemical mechanisms underlying pheomelanin‐mediated oxidative stress, with special reference to the oxygen‐dependent depletion of glutathione and other cell antioxidants. The new concept of pheomelanin as a ‘living’ polymer and biocatalyst that may grow by exposure to monomer building blocks and may trigger autooxidative processes is also discussed. As a corollary, treatment of inflammatory skin diseases in RHP patients is briefly commented. Finally, possible concerted strategies for melanoma prevention in the red hair phenotype are proposed.

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Section: The Dark Chemistry Of Pheomelanin: Prooxidant and Redox Propmentioning

confidence: 71%

Pheomelanin‐induced oxidative stress: bright and dark chemistry bridging red hair phenotype and melanoma

Napolitano

Panzella

Monfrecola

et al. 2014

Pigment Cell Melanoma Res

Self Cite

130

149

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“…This position experiences the acid-activatable electron withdrawing effect of the imine moiety, sustaining either facile H-atom abstraction leading to captodatively stabilized free radical intermediates, [26,27] or condensation with various aldehyde derivatives to produce a range of cyanine-type chomophores. Noticeable applications of this chemistry include colorimetric peroxide and/or redox biometal detection, [26] pH sensing via reversible chromophoric changes that can be repeated over several cycles, [28] or the development of a modular dye platform for one-time-pad molecular cryptography. [29] The manifold synthetic opportunities offered by the BTZ system are schematically illustrated in Figure 2.…”

Section: The Dopaquinone-cysteine Route To Photochromic and Acidichromic Chromophoresmentioning

confidence: 99%

Nature‐Inspired Functional Chromophores from Biomimetic o‐Quinone Chemistry

et al. 2021

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Dedicated to Professor Franco Cozzi on the occasion of his 70th birthday.A concise highlight of the main types of chromophoric systems obtained in the authors' and other laboratories through biomimetic chemistry or synthetic manipulation of natureinspired o-quinones is the primary focus of this Minireview. Following oxidative conversion of a variety of natural catechol substrates like DOPA, dopamine, 5-S-cysteinyldopa and caffeic acid, in the presence of suitable additives, a remarkable variety of chromophoric systems can be produced, which display specific optical and electronic properties, e. g. acidichromism, solvatochromism or strong emission upon excitation. Such properties can be tailored for specific applications through rational synthetic manipulations and/or fine-tuning through non-covalent and supramolecular interactions. Practical access routes to the reported o-quinone-derived chromophoric systems are illustrated along with the main prospective applications.

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“…The trichocyanines, in particular, showed an extension of the conjugated system compared to that exhibited by Δ 2,2’ -bi-(2 H -1,4-benzothiazine) [ 32 , 34 ], which expectedly resulted in a larger bathochromic shift in acid. Therefore, variation of the π-bridge could be recognized as a facile and effective approach for developing push-pull chromophores with specific properties and easy tunability by modulating the electron-donating substituent(s) on the phenyl ring ( Figure 2 ).…”

Section: Introductionmentioning

confidence: 99%

Bioinspired Heterocyclic Partnership in a Cyanine-Type Acidichromic Chromophore

et al. 2020

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A new red hair-inspired 1,4-benzothiazine-based scaffold is disclosed herein, built upon a modular D-π-A architecture via condensation of the easily accessible 3-phenyl-2H-1,4-benzothiazine with indole-3-carboxaldehyde. The compound was obtained in around 50% yields and was characterized by complete spectroscopic analysis. The new benzothiazine-based cyanine displayed a characteristic reversible acidichromic behavior with a marked bathochromic shift upon acidification. The chromophore resisted at least fifteen hydrochloric acid/sodium hydroxide cycles without appreciable alterations. The expedient and scalable synthetic procedure together with the pH sensitive chromophoric properties would make the new compound an attractive prototype for novel modular chromophore for pH-sensing and other applications.

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Red-Hair-Inspired Chromogenic System Based on a Proton-Switched Dehydrogenative Free-Radical Coupling

Cited by 13 publications

References 21 publications

Pheomelanin‐induced oxidative stress: bright and dark chemistry bridging red hair phenotype and melanoma

Pheomelanin‐induced oxidative stress: bright and dark chemistry bridging red hair phenotype and melanoma

Nature‐Inspired Functional Chromophores from Biomimetic o‐Quinone Chemistry

Bioinspired Heterocyclic Partnership in a Cyanine-Type Acidichromic Chromophore

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