945-32-4Relevant articles and documents
Norepinephrine and its metabolites are involved in the synthesis of neuromelanin derived from the locus coeruleus
Wakamatsu, Kazumasa,Tabuchi, Keisuke,Ojika, Makoto,Zucca, Fabio A.,Zecca, Luigi,Ito, Shosuke
, p. 768 - 776 (2015/11/11)
In order to elucidate the chemical structure of black to brown pigments, neuromelanins (NMs), in the substantia nigra (SN) and the locus coeruleus (LC) in the central nervous system of humans and other mammalian species during aging, chemical degradative methods are powerful tools. HPLC analysis after hydroiodic acid hydrolysis detected aminohydroxyphenylethylamines, aminohydroxyphenylacetic acids, and aminohydroxyethylbenzenes, which confirmed that SN-NM and LC-NM contain melanin derived not only from dopamine and norepinephrine (NE) but also from several other catecholic metabolites, such as 3,4-dihydroxyphenylalanine, 3,4-dihydroxyphenylacetic acid, 3,4-dihydroxymandelic acid, 3,4-dihydroxyphenylethanol, and 3,4-dihydroxyphenylethylene glycol, in addition to the corresponding Cys-derivatives in varying degrees. However, hydroiodic acid hydrolysis showed that LC-NM produced the same degradation products as were detected in SN-NM. Thus, we needed to develop a new chemical detection method to validate the existence of NE in LC-NM. In the present study, we report that HCl hydrolysis of LC-NM in the presence of thioglycolic acid yields new products arising from substitution of the hydroxyl group by thioglycolic acid at the benzyl position of NE and cysteinyl-NE. This is the first chemical evidence showing that NE and cysteinyl-NE are incorporated into LC-NM.
Oxidative Degradation of Melanins to Pyrrole Acids: a Model Study.
Napolitano, Alessandra,Pezzella, Alessandro,Vincensi, M. Rosaria,Prota, Giuseppe
, p. 5913 - 5920 (2007/10/02)
The origin of pyrrole-2,3,5-tricarboxylic acid (PTCA), the most characteristic degradation product of melanins, was investigated by use of synthetic pigments prepared from the major biosynthetic precursors, 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA).Under the reported conditions, i.e. acidic permanganate, oxidative degradation of DHI- and DHICA-melanins afforded PTCA in 0.15 and 3.0percent w/w yield, respectively.A significant improvement of PTCA yields up to 7percent was obtained using alkaline hydrogen peroxide as the oxidising agent.Under these conditions pyrrole-2,3-dicarboxylic acid (PDCA) was also obtained in significant yields.Investigations of the oxidative degradation of some model indole obligomers (1-4) provided unambiguous evidence that PTCA may originate from 2-linked DHI-units in the pigment polymer as well as from DHICA-derived units, whereas PDCA arises from DHI-units not substituted at 2-position.Monitoring of the oxidation of dimer 1 to PTCA showed the intermediate formation of DHICA.Accordingly, a mechanistic route is proposed for the degradation of 2-substituted DHI-units in melanin polymer to PTCA, which also accounts for the observed yields of formation of the pyrrole acid from the model oligomers.
