Polysaccharide-mediated synthesis of melanins from serotonin and other 5-hydroxy indoles

Vercruysse, Koen; Clark, Astiney M.; Alatas, Noor; Brooks, Dylan; Hamza, Nafisa; Whalen, Margaret M.

doi:10.1101/184002

Cited by 13 publications

(21 citation statements)

References 22 publications

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“…This report expands our earlier observations on the formation of MN-like pigments from a wide variety of catecholic or indolic precursors. [16][17][18][19][20][21]23] The chemical processes used to generate these MN-like pigments are non-enzymatic, using air-mediated (in the presence of PS or alkaline solutions) or Fe 2+ /H 2 O 2 -mediated oxidation. Strong alkaline solutions are very effective in converting catecholic precursors like L-DOPA (this report), homogentisic acid [23], catechol or pyrogallol [17] into darkcolored, MN-like pigments.…”

Section: Discussionmentioning

confidence: 99%

“…[13][14][15] In previous reports we have presented our observations regarding the synthesis of MN-like pigments from a multitude of precursors using polysaccharides (PS) or a combination of Fe 2+ and H 2 O 2 . [16][17][18][19][20][21] We observed that many PS can promote the formation of MN-like pigments using different types of precursors leading to darkly colored solutions or materials. Despite the obvious presence of a darkly-colored pigment, the PS/pigment complexes tended to contain mostly PS material with very little pigment bonded to it as judged from FT-IR analyses.…”

Section: Introductionmentioning

confidence: 93%

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Synthesis of L-DOPA based pigments with different physic-chemical properties

Vercruysse¹

2018

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Using air- or Fe2+/H2O2-mediated oxidation, the formation of melanin-like pigments from L-DOPA was evaluated. The effects of the various reaction conditions on the efficiency of the reaction and the physic-chemical properties of the pigments generated (UV-Vis absorbance, fluorescence emission) was evaluated. As previously observed for other phenolic and indolic compounds, the use of high concentrations of H2O2 resulted in melanin-like materials with a much lighter color. In addition, we observed that, unlike for air-mediated oxidation, the Fe2+/H2O2-mediated oxidation of L-DOPA can yield melanin-like pigmentation in an acidic environment. In general, our results suggest that depending on the intensity of the oxidizing reaction conditions involved, light- or dark-colored melanin-like pigments can be generated from L-DOPA. This may be an important factor when evaluating the visible outlook of histological specimens: the presence of a lighter color or the absence of a dark color may not necessarily mean the absence of melanin-like biomolecules. We discuss all our observations in the context of the importance of melanin-like pigmentation in human physiology.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 93%

Synthesis of L-DOPA based pigments with different physic-chemical properties

Vercruysse¹

2018

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“…[28][29][30] In recent years we have presented various studies on the air-or reactive oxygen species-mediated oxidation of various catecholic compounds into dark-or light-colored pigments. [31][32][33][34][35][36][37][38] This report presents our first attempt to generate pheomelanin-like pigments by including L-cysteine into the reaction mixtures. As before, we evaluated our reactions through UV-Vis spectroscopic measurements and size exclusion chromatography (SEC) analyses.…”

Section: Scheme 1: Basic Outline Of the Biosynthesis Of Eumelanin Andmentioning

confidence: 99%

Melanogenesis: A Search for Pheomelanin and Also, What Is Lurking Behind Those Dark Colors?

Vercruysse¹,

Govan²

2019

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We investigated the synthesis of melanin-like materials from DOPA, dopamine, norepinephrine and epinephrine in the presence of L-cysteine. We observed that L-cysteine delayed the formation of pigment from these catecholamines and that the presence of L-cysteine yielded darker-colored reaction mixtures. No reddish pigment was observed that would indicate the synthesis of pheomelanin-like material. The reactions were performed in the presence of Na2CO3 and through the addition of CaCl2 at the end of the reaction; the black, eumelanin-like material was co-precipitated with CaCO3. The remaining supernatant solutions were observed to be light-yellow to rusty-orange in color depending on the catecholamine used in the reaction. Size exclusion chromatography (SEC) analyses indicated that the removal of the black pigment left behind an oligomeric material that exhibited a strong absorbance band around 280nm. Our experimental and analytical observations prompt us to raise a number of points of discussion or hypotheses. 1) The presence of L-cysteine during the air-mediated oxidation of catecholamines leads to darker-colored pigments; not reddish or lighter-colored pigments that would visually resemble pheomelanin-like pigments, 2) SEC analyses suggested that the black pigment generated during the air-mediated oxidation of catecholamines is not necessarily the main reaction product, 3) The pre-formed, dark-colored pigments obtained through the air-mediated oxidative melanogenesis process can readily be deposited on insoluble mineral surfaces using an in situ co-precipitation procedure, 4) The air-mediated oxidation of catecholamines leads to a binary product that contains an insoluble, melanin-like substance and a soluble, oligo- or polymeric substance containing unoxidized precursor units, 5) The melanogenesis process leads to a binary product involving a non-covalently bonded combination of dark-colored pigment and a lighter-colored or colorless substance; the latter being understudied or ignored in the in vitro or in vivo studies of the melanogenesis process, 6) The kinetics of the melanogenesis process may determine the balance between insoluble and soluble components of the binary product generated; the slower the reaction the more dark-colored, insoluble pigment generated, 7) One should consider the possibility of intermolecularly, N-to-C, bonded units of catecholamines when evaluating the structure of melanins, polydopamines, etc. and 8) There is a need for a systematic study of the effect of amino acids (beyond just L-cysteine) and amines in general on the melanogenesis process.

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“…The value of SEC analysis to monitor the formation of colored pigments from catecholic or phenolic compounds has been discussed in previous reports. [9][10][11][12][13]26 In SEC, molecules are separated on the basis of differences in their hydrodynamic volume (often related to the molecular mass of the molecule): the lower the retention time, the higher the hydrodynamic volume of the analyte. In our SEC analyses, the lower limit of exclusion, as determined by the injection of water, was about 15 minutes.…”

Section: Fig3: Effect Of H2o2 On Color Formation and Reactivity For mentioning

confidence: 99%

“…Some of these compounds have been the subject of previous studies on the formation of MN-like pigments performed in our laboratories. [9][10][11][12][13] In biological samples, the MN pigments may present themselves as particulate matter of different sizes and shapes. The physic-chemical properties of MN particles, e.g., aggregation, have been studied and reviewed extensively before.…”

Section: Introductionmentioning

confidence: 99%

Dark- or Light-Colored Melanins: Generating Pigments Using Fe2+ and H2O2

Vercruysse¹,

Russell²,

Knight³

et al. 2017

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We have studied the formation of melanin-like pigments from catechol or pyrogallol and a wide range of other phenolic compounds using Fe2+ and H2O2. Combining UV_Vis spectroscopic measurements and size-exclusion chromatography analyses we evaluated the impact of the intensity of the oxidation reaction by varying the concentration of H2O2 present in the reaction mixtures. All compounds tested, except tyrosine, reacted readily leading to mixtures that were black, brown or yellow-orange in color. For many compounds tested, the use of increasing concentrations of H2O2 resulted in either precipitation of the pigment or the formation of a soluble, lighter-colored pigment. With catechol or pyrogallol as model compounds, and using different concentrations of H2O2, several materials were synthesized, purified and dried. The physic-chemical properties of these materials were compared to the properties of melanin-like pigments synthesized from the same precursors using air-oxidation in an alkaline environment. For both precursors, a distinct chemical change, as judged from FT-IR spectroscopy, was introduced in the melanin structures when using H2O2 as the oxidizing agent and the relative intensity of this distinct signal strengthened with increasing concentration of H2O2 used in the reaction. In general, our results suggest that depending on the precursor molecule and the intensity of the oxidizing reaction conditions involved, light- or dark-colored melanin-like pigments can be generated. This may be an important factor when evaluating the visible outlook of histological or archeological specimens: the presence of a lighter color or the absence of a dark color may not necessarily mean the absence of melanin-like biomolecules.

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Polysaccharide-mediated synthesis of melanins from serotonin and other 5-hydroxy indoles

Cited by 13 publications

References 22 publications

Synthesis of L-DOPA based pigments with different physic-chemical properties

Synthesis of L-DOPA based pigments with different physic-chemical properties

Melanogenesis: A Search for Pheomelanin and Also, What Is Lurking Behind Those Dark Colors?

Dark- or Light-Colored Melanins: Generating Pigments Using Fe2+ and H2O2

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