Using size exclusion chromatography to monitor the synthesis of melanins from catecholamines

Vercruysse, Koen; Clark, Astiney M.; Bello, Paola A.F.; Alhumaidi, Majidah

doi:10.1016/j.jchromb.2017.04.005

Cited by 20 publications

(46 citation statements)

References 14 publications

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“…However, such enzymes may not be a necessity to generate the appearance of the typical dark colors associated with the presence of MN-like pigments. Non-enzymatic biomolecules like polysaccharides (PS) [22][23] can promote the oxidation of catecholic or indolic precursors into darkly-colored materials and the association of MN-like pigments with extracellular PS materials has been reported and discussed before. 1,[33][34] Similarly, the amyloid-like protein Pmel17/Silver/gp100 is capable of generating MN-like pigments in vitro or in vivo.…”

Section: Discussionmentioning

confidence: 99%

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Light- or Dark-Colored, L-DOPA-Based Melanins

Vercruysse¹,

Whalen²

2018

Preprint

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This report is a continuation of previous research on the H 2 O 2 -mediated synthesis of melanin-like pigments. We synthesized and characterized L-DOPA-based pigments using air-or H 2 O 2 -mediated oxidation. We compared their physic-chemical properties and evaluated their capacity to affect the interleukin release from immune cells. The use of higher concentrations of H 2 O 2 resulted in melanin-like materials with a distinct chemical signature in their FT-IR spectra and a lighter color. All pigments enhanced the interleukin release from immune cells. The possibility that lighter-colored melanins can be generated is discussed in the context of the importance of melanin-based pigmentation in human physiology.

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Section: Discussionmentioning

confidence: 99%

“…All mixtures were dialyzed and lyophilized as described elsewhere. 22 During the reaction and the dialysis process, aliquots from the mixtures were diluted with solvent for chromatographic analysis, centrifuged and analyzed to monitor the progress of the reaction and the dialysis purification process.…”

Section: Synthesis and Purification Of L-dopa-based Pigmentsmentioning

confidence: 99%

Light- or Dark-Colored, L-DOPA-Based Melanins

Vercruysse¹,

Whalen²

2018

Preprint

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“…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] Fig. 1: Chemical structures of compounds used in this study: catechol (1), pyrogallol (2), dopamine (3), norepinephrine (4), epinephrine (5), tyrosine (6), serotonin (7) and homogentisic acid (8).…”

Section: Introductionmentioning

confidence: 99%

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

Vercruysse

Russell²,

Knight³

et al. 2017

Preprint

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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 Fe 2+ and H 2 O 2 . 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 H 2 O 2 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 H 2 O 2 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 H 2 O 2 , 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 H 2 O 2 as the oxidizing agent and the relative intensity of this distinct signal strengthened with increasing concentration of H 2 O 2 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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“…Overall, the results presented in Fig.2 show that GA enhanced the oxidation of (1), independent of the presence of Cu 2+ . Many PS, e.g., chondroitin sulfate (CS) A or C, that were capable of promoting the oxidation of CAs [4], were capable of promoting the oxidation of (1), but not without the presence of transition elements like Cu 2+ or Fe 2+ (results not shown).…”

Section: Uv_vis Spectroscopy Studiesmentioning

confidence: 99%

“…[1] In a previous report, we described the effect of various PS on the oxidation of catecholamines (CAs) into melanin (MN)-like pigments. [4] That report did not include our observations regarding the effects of GA on the oxidation of CAs. It appeared that, compared to the other PS materials tested, GA had only a modest effect on the MN formation from CAs.…”

Section: Introductionmentioning

confidence: 99%

Gum Arabic promotes oxidation and ester hydrolysis

Vercruysse

Tyler

Readus

2017

Preprint

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We studied the interactions between gum Arabic and select catecholic compounds like caffeic acid, chlorogenic acid and catechol. We observed that GA is capable of promoting the auto-oxidation of the above-mentioned compounds into darkly colored pigments without the addition of redox-sensitive cations. Gum Arabic appeared to be unique among polysaccharide-based materials as many other types of polysaccharides promote the oxidation of the above-mentioned compounds only in the presence of redox cations like Fe 2+ or Cu 2+. RP-HPLC and SEC chromatographic techniques were employed to monitor the reactions and to observe the formation of high molecular mass, pigmented materials from gum Arabic and all three catecholic compounds. FT-IR spectroscopic analysis revealed that, despite their darkly colored appearances, the gum Arabic/pigment materials synthesized contain mostly gum Arabic and very little pigment. As chlorogenic acid is an ester of caffeic acid, we studied the capacity of gum Arabic to promote ester hydrolysis using acetylsalicylic acid as the model compound. We observed that gum Arabic did promote the hydrolysis of acetylsalicylic acid into salicylic acid. However, in all our experiments involving the pigment formation between gum Arabic and chlorogenic acid, we did not observe any evidence that chlorogenic acid was hydrolyzed leading to the release of caffeic acid during these reactions. In addition, we observed that heat treatment of gum Arabic did not affect its pro-oxidizing capability, but it did negatively affect its capability to hydrolyze salicylic acid. Thus, these two types of chemical reactivity present in the gum Arabic material may be associated with different components of the gum Arabic material.

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Using size exclusion chromatography to monitor the synthesis of melanins from catecholamines

Cited by 20 publications

References 14 publications

Light- or Dark-Colored, L-DOPA-Based Melanins

Light- or Dark-Colored, L-DOPA-Based Melanins

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

Gum Arabic promotes oxidation and ester hydrolysis

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