Melanins and lens pigments: a comparative study
P. R. health sci. j
; 12(2): 129-35, jun. 1993.
Artigo
em Inglês
| LILACS
| ID: lil-176726
Biblioteca responsável:
BR1.1
RESUMO
Based on previous findings that lens pigments and melanins share many physicochemical properties, human lens pigments and natural (hair) and synthetic melanins were submitted to oxidation with permanganate under strong acidic conditions. This procedure has been utilized for the characterization of melanins and results in the well defined products, thiazole-4,5-dicarboxylic acid (TDCA) and pyrrole-2,3,5-tricarboxylic acid (PTCA), which can be quantitated by high performance liquid chromatography (HPLC). PTCA is regarded as a marker of black eumelanins and was therefore a main component of synthetic DOPA-eumelanin and dark hair. Its identity was established by synthesis from 5-hydroxyindole-2-carboxylic acid. TDCA derives from pheomelanins and was therefore an important component of red hair and synthetic GSH-pheomelanin. TDCA was identified by its retention time relative to PTCA. The analysis of a series of cataract digests of increasing pigmentation (type I < type IV < type V) and a purified fraction of lens pigments (DE52 pigment) revealed the presence in these preparations of both PTCA and TDCA. The concentration of TDCA significantly increased with the degree of pigmentation of the digests and reached a maximum in the DE52 pigment. The TDCA/PTCA ratio was high in the lens preparations and comparable to that given by hair pheomelanin. These findings support that pheomelanin is an integral part of lens pigments. By comparing the yields of TDCA in GSH-pheomelanin and in the purified lens pigment, a 9 per cent contribution of pheomelanin to the lens pigment was estimated
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Coleções:
Bases de dados internacionais
Base de dados:
LILACS
Assunto principal:
Pirróis
/
Tiazóis
/
Ácidos Dicarboxílicos
/
Cristalino
/
Melaninas
Tipo de estudo:
Estudo prognóstico
Idioma:
Inglês
Revista:
P. R. health sci. j
Assunto da revista:
Medicina
Ano de publicação:
1993
Tipo de documento:
Artigo