Figure - available from: Plant Biotechnology Journal
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Biosynthetic pathway of natural carotenoids. In this figure, the illuminated spots display the colours of various substances. Specifically, the carotenoids belonging to C30 and C50 categories are denoted in blue. The main biosynthetic pathways are divided into α and β pathways, which are distinctly colour‐coded as green and orange, respectively. The dashed arrow indicates that multiple reactions occur within that particular step. Crucial precursors in the biosynthesis process are emphasized with black boxes. MEP, 2‐C‐methyl‐derythritol‐4‐phosphate pathway; MVA, mevalonate pathways; FPP, farnesyl pyrophosphate; GGPP, geranylgeranyl diphosphate; GGPPS, GGPP synthase; PSY, phytoene synthase; PDS, phytoene desaturase; ZDS, ξ‐carotene desaturase; CRTISO, carotenoid isomerase; LCYB, lycopene β‐cyclase; LYCE, lycopene ε‐cyclase; CHYB, β‐carotene hydroxylase; CHYE, ε‐carotene hydroxylase; ZEP, zeaxanthin epoxidase; VDE, violaxanthin de‐epoxidase (DellaPenna and Pogson, 2006).
Source publication
Pigments, as coloured secondary metabolites, endow the world with a rich palette of colours. They primarily originate from plants and microorganisms and play crucial roles in their survival and adaptation processes. In this article, we categorize pigments based on their chemical structure into flavonoids, carotenoids, pyrroles, quinones, azaphilone...
Citations
... [10,11] Apart from L-DOPA, other catecholamines like dopamine or norepinephrine, with or without cysteine, have been described as the precursors of neuromelanin, a MN material found in the brain of humans or animals. [12] Plant, fungal and some bacterial MN are built from nitrogen-free precursors, e.g., homogentisic acid, catechol or dihydroxynaphthalene. [2,3,13,14] The experiments described in this report involve MN-like materials synthesized from a wide variety of catecholic (ortho diphenolic) ...
... [25][26][27] The notion that MN materials exist as colloidal particles is nothing new and many applications are explored on the basis of the colloidal properties of MN materials. [3,6,14,[29][30][31][32][33][34][35][36][37] In this context it is worth noting that, despite the uncertainties regarding the chemical structure(s) behind MN materials, there seems to be a consensus that MN materials are supramolecular structures generated through a multi-step process, proceeding from oligomers to aggregation into protoparticles, and the final, so-called, type A and type B particles. [38,39] Most studies related to MN-like materials focus on the use of dopamine or L-DOPA, or their associated derivatives 5,6-dihydroxyindole (DHI) or 5,6-dihydroxyindole carboxylic acid (DHICA), as precursor for the synthesis of MN. ...
Melanin materials were synthesized using a variety of precursors. Crude reaction mixtures and select purified materials were evaluated using absorbance spectroscopy from the UV to the visible and near-infrared regions of the electromagnetic spectrum. Combining new and previous experimental results, 968 different reactions were evaluated objectively for their type of appearance as eumelanin-or pheomelanin-like. In addition, two mathematical models were compared to evaluate the intensity of the color associated with the melanin material. One based upon the commonly used exponential equation, and another based on a reciprocal power equation. The results obtained from both approaches yield similar results: objective, numerical parameters, combining concentration-and material-specific factors, to compare different melanin materials built from varying types of precursors. FT-IR spectroscopic analyses of select purified materials highlight the common features of the melanin materials, independent of the precursor employed. In addition, FT-IR spectroscopy was used to evaluate the presence of carboxylic acid or carboxylate functional groups. Such features may be present due to the precursor employed and/or due to the oxidative cleavage of aromatic rings that may occur during the synthesis of the material. Depending on the purification process involved, the melanin material may contain carboxylates (dialysis) or carboxylic acids (HCl-induced precipitation or acidification followed by dialysis).
