title: Characterisation of polyacetylenes isolated from carrot (Daucus carota) extracts by negative ion tandem mass spectrometry.
abstract: The potential use of negative electrospray ionisation mass spectrometry (ESI-MS) in the characterisation of the three polyacetylenes common in carrots (Daucus carota) has been assessed. The MS scans have demonstrated that the polyacetylenes undergo a modest degree of in-source decomposition in the negative ionisation mode while the positive ionisation mode has shown predominantly sodiated ions and no [M+H](+) ions. Tandem mass spectrometric (MS/MS) studies have shown that the polyacetylenes follow two distinct fragmentation pathways: one that involves cleavage of the C3-C4 bond and the other with cleavage of the C7-C8 bond. The cleavage of the C7-C8 bond generated product ions m/z 105.0 for falcarinol, m/z 105/107.0 for falcarindiol, m/z 147.0/149.1 for falcarindiol-3-acetate. In addition to these product ions, the transitions m/z 243.2 → 187.1 (falcarinol), m/z 259.2 → 203.1 (falcarindiol), m/z 301.2 → 255.2/203.1 (falcarindiol-3-acetate), mostly from the C3-C4 bond cleavage, can form the basis of multiple reaction monitoring (MRM)-quantitative methods which are poorly represented in the literature. The 'MS(3) ' experimental data confirmed a less pronounced homolytic cleavage site between the C11-C12 bond in the falcarinol-type polacetylenes. The optimised liquid chromatography (LC)/MS conditions have achieved a baseline chromatographic separation of the three polyacetylenes investigated within 40 min total run-time.
authors: Department of Food Biosciences, Teagasc Food Research Centre Ashtown, Dublin 15, Ireland. dilip.rai@teagasc.ie
authors: Dilip K
authors: DK
authors: Rai
authors: Nigel P
authors: NP
authors: Brunton
authors: Anastasios
authors: A
authors: Koidis
authors: Ashish
authors: A
authors: Rawson
authors: Padraig
authors: P
authors: McLoughlin
authors: William J
authors: WJ
authors: Griffiths
mesh_terms: D018552:Daucus carota / Q000737:chemistry*; D053280:Diynes / Q000737:chemistry / Q000302:isolation & purification; D005233:Fatty Alcohols / Q000737:chemistry / Q000302:isolation & purification; D019906:Nuclear Magnetic Resonance, Biomolecular; D010936:Plant Extracts / Q000737:chemistry*; D053279:Polyynes / Q000737:chemistry* / Q000302:isolation & purification; D013056:Spectrophotometry, Ultraviolet; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D053280:Diynes; D005233:Fatty Alcohols; D010936:Plant Extracts; C018541:falcarinol; D053279:Polyynes; C034379:falcarindiol