title: Reduction of the nitro group to amine by hydroiodic acid to synthesize o-aminophenol derivatives as putative degradative markers of neuromelanin.
abstract: Neuromelanin (NM) is produced in dopaminergic neurons of the substantia nigra (SN) and in noradrenergic neurons of the locus coeruleus (LC). The synthesis of NM in those neurons is a component of brain aging and there is the evidence that this pigment can be involved in the pathogenesis of neurodegenerative diseases such as Parkinson's disease. NM is believed to derive from the oxidative polymerization of dopamine (DA) or norepinephrine (NE) with the participation of cysteine, dolichols and proteins. However, there are still unknown aspects in the chemical structure of NM from SN (SN-NM) and LC (LC-NM). In this study, we designed a new method to synthesize o-aminophenol compounds as putative degradation products of catecholamines and their metabolites which may be incorporated into NM. Those compounds are aminohydroxyphenylethylamine (AHPEA) isomers, aminohydroxyphenylacetic acid (AHPAA) isomers and aminohydroxyethylbenzene (AHEB) isomers, which are expected to arise from DA or NE, 3,4-dihydroxyphenylacetic acid (DOPAC) or 3,4-dihydroxyphenylmandelic acid (DOMA) and 3,4-dihydroxyphenylethanol (DOPE) or 3,4-dihydroxyphenylethyleneglycol (DOPEG), respectively. These o-aminophenol compounds were synthesized by the nitration of phenol derivatives followed by reduction with hydroiodic acid (HI), and they could be identified by HPLC in HI hydrolysates of SN-NM and LC-NM. This degradative approach by HI hydrolysis allows the identification of catecholic precursors unique to SN-NM and LC-NM, which are present in catecholaminergic neurons.
authors.affiliation: Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi 470-1192, Japan. kwaka@fujita-hu.ac.jp.
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Wakamatsu
authors.affiliation: Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi 470-1192, Japan. hmatsuoka@u-gifu-ms.ac.jp.
authors.forename: Hitomi
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi 470-1192, Japan. 82013103@fujita-hu.ac.jp.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Tabuchi
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan. ojika@agr.nagoya-u.ac.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ojika
authors.affiliation: Institute of Biomedical Technologies, National Research Council of Italy, Via Cervi, 93, Segrate, Milano 20090, Italy. fabio.zucca@itb.cnr.it.
authors.forename: Fabio A
authors.initials: FA
authors.lastname: Zucca
authors.affiliation: Institute of Biomedical Technologies, National Research Council of Italy, Via Cervi, 93, Segrate, Milano 20090, Italy. luigi.zecca@itb.cnr.it.
authors.forename: Luigi
authors.initials: L
authors.lastname: Zecca
authors.affiliation: Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Aichi 470-1192, Japan. sito@fujita-hu.ac.jp.
authors.forename: Shosuke
authors.initials: S
authors.lastname: Ito
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000737:chemistry; D000143:Acids / Q000737:chemistry*; D000627:Aminophenols / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D017613:Iodine Compounds / Q000737:chemistry*; D008125:Locus Coeruleus / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008543:Melanins / Q000737:chemistry*; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives / Q000737:chemistry; D013378:Substantia Nigra / Q000737:chemistry
chemical_list: D000143:Acids; D000627:Aminophenols; D017613:Iodine Compounds; D008543:Melanins; C014121:neuromelanin; D015102:3,4-Dihydroxyphenylacetic Acid; C005975:3,4-dihydroxyphenylethanol; C027667:2-aminophenol; C010466:hydroiodic acid; D010626:Phenylethyl Alcohol