Melanins isolation

Turkovskii, 1.1. Yurlova, N. A. (2002). The photochemical and surface-active properties of melanins isolated from some black fungi. Microbiology, 71, 410-16. 

J.A. Menon, S. Persad, H.F. Haberman, C.J. Kurian (1983). A comparative study of the physical and chemical properties of melanins isolated from red and black hair. J. Invest. Dermatol, 80, 202-206. 

Palumbo A, d Ischia M, Prota G (1987) Tyrosinase Promoted Oxidation of 5,6-Dihydroxyindole-2-caiboxylic Add to Melanin. Isolation and Characterization of Oligomer Intermediates. Tetrahedron 43 4203... 

CgHiiNO. M.p. 282 C (decomp.). The naturally occurring substance is laevorotatory. It is an amino-acid isolated from various plant sources, but not found in the animal body. It is formed from tyrosine as the first stage in the oxidation of tyrosine to melanin. It is used in the treatment of Parkinson s disease. 

Because of their very complex chemical structures and heterogeneity, melanins are difficult to extract, separate, and characterize from tissues. Eumelanins are insoluble in water and organic solvents. They can be extracted from tissues with strong chemicals that are capable of removing lipids, proteins, and other tissue components but also lead to the formation of degradation products. Enzymatic procedures were developed for the isolation of eumelanins from mammalian hair and irises. The first step is sequential digestion with protease, proteinase K, and papaine in the presence... 

Novellino, L., Napolitano, A., and Fhota, G., Isolation and characterization of mammalian eumelanins from hair and irides, Biochim. Biophys. Acta, 1475, 295, 2000. Capozzi, V. et al., Optical and photoelectronic properties of melanin, Thin Solid Films, 511, 362, 2006. 

Wang, H. et al., Isolation and characterization of melanin from Osmanthus fragrans seeds, LWT Food Sci. TechnoL, 39, 496, 2006. 

Very recently, the method has been used for the synthesis of racemic linderol A [311], a natural product isolated from the fresh bark of Lindera umbellata. This compound is reported to exhibit potent inhibitory activity on the melanin biosynthesis of cultured B-16 melanoma cells in guinea pigs, without causing any cytotoxicity in the cultured cell or skin irritation [312]. 

Tyrosine (Tyr or Y) (4-hydroxyphenylalanine ((5)-2-amino-3-(4-hydroxyphenyl)-propanoic acid)) is a polar, neutral, aromatic amino acid with the formula H00CCH(NH2)CH2C6H50H and is the precursor of thyroxin, dopamine, norepinephrine (noradrenaline), epinephrine (adrenaline), and the pigment melanin. Being the precursor amino acid for the thyroid gland hormone thyroxin, a defect in this may result in hypothyroidism. Tyr is extremely soluble in water, a property that has proven useful in isolating this amino acid from protein hydrolysates. The occurrence of tyrosine- 0-sulfate as a constituent of human urine and fibrinogen has been reported. ... 

Dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid were shown to form after the red pigment stage that occurred during the conversion of DOPA into a melanin, by Raper, who isolated these compounds as their dimethyl ethers.72 The presence of 5,6-dihydroxyindoles in solutions of DOPA, dopamine, and noradrenaline which are undergoing oxidation has subsequently been confirmed by paper and thin-layer chromatography.118,120,222 5,6-Dihydroxyin-dole and 5,6-dihydroxyindole-2-carboxylic acid have recently been isolated from the alkali fusion products of sepiomelanin, indicating... 

The non-oxidative formation of melanin from adrenochrome in acid solution, reported by Harley-Mason,6 has recently been shown by Bu Lock to be controlled by a second-order reaction between adrenochrome and acid.107 It was suggested that the initial product (not isolated) was probably l-methylindole-5,6-quinone, which polymerized rapidly to melanin via dimers and oligomers.107 (The intermediate monomer quinone also gave a melanin-like copolymer with indole.107)... 

Oxidation of L-DOPA to L-dopaquinone is an important biological process, and dopaquinone is known to play a key role in the oxidative conversion of tyrosine into melanins, the primary pigments of skin and hair. It has been found that under biomimetic conditions both resorcinol and phloroglucinol inhibit this action of L-DOPA, and the compound 1 was isolated from the enzyme-catalysed L-DOPA/phloroglucinol reaction. Compound 1 could also be prepared by fenicyanide oxidation of a mixture of L-DOPA and phloroglucinol. 

Lee CH, Chung MC, Lee HJ, Bae KS, Kho YH (1997) MR566A and MR566B, New Melanin Synthesis Inhibitors Produced by Trichoderma harzianum I. Taxonomy, Fermentation, Isolation and Biological Activities. J Antibiot 50 469... 

Melanin, which is prepared by polymerization with a macromolecule-metal complex, is isolated as a black powder and shows strong absorption in the ultraviolet and visible regions. The free radical species is stable against heat, acid, and base, and the EPR shows a singlet signal at g = 2.00. These properties are also important in the physiological characteristics of melanin. 

Further analysis of the UV spectrum revealed that this compound is a gallic acid derivative. A search of the Dictionary of Natural Products for molecular ion and plant genus name leads to the identification of a known compound - Pterocaryanin B. The compounds with poly-hydroxyl groups in their structures are very well known as tyrosinase inhibitors and are responsible for the inhibition of melanin synthesis. Therefore, no further isolation was necessary. 

Fig. 11.2. Rock-inhabiting fungi often demonstrate a specific yeast-like growth pattern. Image shows a fungal colony, isolated from a marble surface in Crimea (Ukraine). The whole structure resembles a cauliflower and is intensively pigmented by melanin. The colony is very compact and mechanically hard and thus capable of producing intense pressure on the surrounding material.

Lee SH, Choi SY, Kim H et al. Mulberroside F isolated from the leaves of Moms alba inhibits melanin biosynthesis. Biol Pharm Bull 2002 25 1045-8. 

Pyrrolecarboxylic acids are the final products of oxidative degradation of eumelanins. The origin, reaction conditions, as well as the isolation and identification techniques used are the factors responsible for the different ratios of di-, tri-, and tetracarboxylic acids formed (7). Thus, untreated sepiomelanin and a number of synthetic melanins oxidized via KMNO4 showed the following trend in the relative ratios of pyrrolecarboxylic acids 2,3,5 2,3 = 2,3,4,5. The same samples after decarboxylation at 200°C followed the sequence 2,3,5 > 2,3 > 2,5 2,4 = 2,3,4,5. The decrease in 2,3,5 triacids and the increase in 2,3 diacids are attributed to the loss of carboxyl groups owing to the thermal treatment (7). Resistance to further oxidative degradation u der specific experimental conditions may substantially influence the ratio of the individual pyrrolecarboxylic acids formed (315). 

Dihydroxyphenylalanine (for structure see diagram 11) is an amino acid isolated (from the pods and sprouts of Vida fd>a) and first definitely identified in 1913 by Guggenheim (323), who showed it to be identical with synthetic material previously prepared (280). It is widely distributed in certain types of plants (beans, etc.) but is not a normal protein constituent. However, it plays an important part in mammalian metabohsm of tyrosine, as it is the precursor of adrenaline (epinephrine), noradrenaline (arterenol, norepinephrine), and melanin. In this review these substances will be considered only insofar as they account for a portion of normal tyrosine metabolism. 

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