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Multiple-stage Mass Spectrometry (multiple-stage + mass_spectrometry)
Selected AbstractsMetabolite identification of a new antitumor agent icotinib in rats using liquid chromatography/tandem mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 14 2008Zhongmin Guan Icotinib, 4-[(3-ethynylphenyl)amino]-6,7-benzo-12-crown-4-quinazoline, is a new antitumor agent. The metabolic pathway of icotinib in rats was studied using liquid chromatography/tandem mass spectrometry (LC/MSn) analysis. Full scan and selected ion monitoring modes were used to profile the possible metabolites of icotinib in rat urine, feces and bile samples. Four phase I metabolites (M1,M4) and two phase II metabolites (M5, M6) were detected and characterized. Multiple-stage mass spectrometry and nuclear magnetic resonance (NMR) spectrometry were employed to elucidate structures of metabolites. Icotinib was metabolized to open the crown ether ring to form the main phase I metabolites. During metabolism, a reactive metabolite was formed. Using semicarbazide as a trapping agent, an intermediate arising from opening of the crown ether ring was detected as an aldehyde product by LC/MS/MS. These data indicated that ring opening of the crown ether was triggered by hydroxylation at the 8,-position of the ring to form a hemiacetal intermediate, which was further oxidized or reduced. Finally, the metabolic pathway of icotinib in rats was proposed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Structure analysis of triterpene saponins in Polygala tenuifolia by electrospray ionization ion trap multiple-stage mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2007Jiangyun Liu Abstract Eighteen different triterpene saponins isolated from Polygala tenuifolia were investigated by electrospray ionization ion trap multiple-stage mass spectrometry (ESI-ITMSn) in positive and negative ion modes. MS1 -MS3/MS4 spectra of the both modes were analyzed, and they all gave fragments in line and shared common fragmentation patterns. Key fragments from MSn spectra of both the modes and their proposed fragmentation pathways were constructed with examples illustrated for the formation of characteristic fragments in the saponins. Two special fragmentation patterns were proposed: (1) the formation of fragments by cleavage of CH2O from ,12 -14,-CH2OH of the oleanene-type saponin aglycone in both positive and negative MSn (n , 2) modes; (2) the occurrence of fragments by cleavage of CO2 and 3-glucose as the characteristic structure feature of 23-COOH at the oleanene-type saponin aglycones coupled with 3-Glc substitutes in the negative MSn (n , 2) modes. Peak intensities in MSn spectra were also correlated with structural features and fragmentation preferences of the investigated saponins, which are discussed in detail. In general, fragments formed predominantly by cleavages of glycosidic bonds in the positive mode, while selective cleavages of acyl bonds preceded that of glycosidic bonds in negative MSn (n , 2) mode, both of which could well be applied to the structural analysis of these saponins. Interpretation of MSn spectra presented here provided diagnostic key fragment ions important for the structural elucidation of saponins in P.tenuifolia. Copyright © 2007 John Wiley & Sons, Ltd. [source] Oligosaccharide sequences in Quillaja saponins by electrospray ionization ion trap multiple-stage mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2004Susanna Broberg Abstract Ten different samples with 13 previously identified saponin structures from Quillaja saponaria Molina were investigated by electrospray ionization ion trap multiple-stage mass spectrometry (ESI-ITMSn) in positive and negative ion modes. Both positive and negative ion mode MS1,MS4 spectra were analyzed, showing that structural information on the two oligosaccharide parts in the saponin can be obtained from positive ion mode spectra whereas negative ion mode spectra mainly gave information on one of the oligosaccharide parts. Analysis of MS1,MS4 spectra identified useful key fragment ions important for the structural elucidation of Quillaja saponins. A flowchart involving a stepwise procedure based on key fragments from MS1,MS3 spectra was constructed for the identification of structural elements in the saponin. Peak intensity ratios in MS3 spectra were found to be correlated with structural features of the investigated saponins and are therefore of value for the identification of terminal monosaccharide residues. Copyright © 2004 John Wiley & Sons, Ltd. [source] Mono and double polar [4 + 2+] Diels,Alder cycloaddition of acylium ions with O -heterodienesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2002Eduardo C. Meurer Abstract Gas-phase reactions of acylium ions with ,,,-unsaturated carbonyl compounds were investigated using pentaquadrupole multiple-stage mass spectrometry. With acrolein and metacrolein, CH3,C+O, CH2CH,C+O, C6H5,C+O, and (CH3)2N,C+O react to variable extents by mono and double polar [4 + 2+] Diels,Alder cycloaddition. With ethyl vinyl ketone, CH3,C+O reacts exclusively by proton transfer and C6H5,C+O forms only the mono cycloadduct whereas CH2CH,C+O and (CH3)2N,C+O reacts to great extents by mono and double cycloaddition. The positively charged acylium ions are activated O -heterodienophiles, and mono cycloaddition occurs readily across their C+O bonds to form resonance-stabilized 1,3-dioxinylium ions which, upon collisional activation, dissociate predominantly by retro-addition. The mono cycloadducts are also dienophiles activated by resonance-stabilized and chemically inert 1,3-dioxonium ion groups, hence they undergo a second cycloaddition across their polarized CC ring double bonds. 18O labeling and characteristic dissociations displayed by the double cycloadducts indicate the site and regioselectivity of double cycloaddition, which are corroborated by Becke3LYP/6,311++G(d,p) calculations. Most double cycloadducts dissociate by the loss of a RCO2COR1 molecule and by a pathway that reforms the acylium ion directly. The double cycloadduct of the thioacylium ion (CH3)2N,C+S with acrolein dissociates to (CH3)2N,C+O in a sulfur-by-oxygen replacement process intermediated by the cyclic monoadduct. The double cycloaddition can be viewed as a charge-remote type of polar [4 + 2+] Diels,Alder cycloaddition reaction. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||