title: Characterisation of natural indigo and shellfish purple by mass spectrometric techniques.
abstract: Two analytical methods based on mass spectrometry were used in the characterisation of constituents of natural indigo prepared from the leaves of Indigofera tinctoria, and of shellfish purple prepared from the hypobranchial glandular secretions of Murex trunculus, following old recipes. On-line pyrolysis gas chromatography in the presence of hexamethyldisilazane followed by mass spectrometric analysis (Py-silylation/GC/MS), and direct exposure mass spectrometry (DE-MS), were used. Extensive fragmentation of indigoid dyes was obtained by Py-silylation/GC/MS. The following molecular markers were highlighted, which are useful for identification purposes: 1,2-dihydro-3H-indol-3-one for indigoid dyes, 1,3-dihydro-2H-indol-2-one for indirubine, and 6-bromo-1,2-dihydro-3H-indol-3-one for shellfish purple. Using DE-MS, 6,6'dibromoindigotine, monobromoindigotine and indigotine were identified as the main components, and the presence of tyrindoxyl, one of the dye precursors, was also assessed.
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Risorgimento 35, 56126 Pisa, Italy.
authors.forename: Alessia
authors.initials: A
authors.lastname: Andreotti
authors.forename: Ilaria
authors.initials: I
authors.lastname: Bonaduce
authors.forename: Maria Perla
authors.initials: MP
authors.lastname: Colombini
authors.forename: Erika
authors.initials: E
authors.lastname: Ribechini
mesh_terms: D000818:Animals; D003116:Color; D004396:Coloring Agents / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D007203:Indigo Carmine; D029883:Indigofera / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D015394:Molecular Structure; D012758:Shellfish
chemical_list: D004396:Coloring Agents; D007211:Indoles; D007203:Indigo Carmine