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FD and FAB mass spectra of some oligopeptides of the tryptophyllin family
No full textMass spectra of some natural thryptophyllins and synthetic analogues have been obtained by using field desorption and fast atom bombardment as soft ionization techniques to overcome the low volatility of these oligopeptides. Field desorption spectra generally show the molecular ion as base peak; some fragments of thermal origin are present at higher emitter heating current, thus providing additional structural information. Fast atom bombardment mass spectra show a more regular fragmentation of the peptide backbone, which allow the complete amino acid sequence to be checked. The presence of two consecutive proline residues in some of the examined molecules affects their fragmentation pattern in both field desorption and fast atom bombardment mass spectrometry giving rise to spectral features which are useful from the diagnostic point of view. The two ionization methods are compared and the advantage of the combined use of both techniques is pointed out
Comparison of FAB and FD mass spectrometry in the analysis of unusually linked nucleotides
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v-Triazolines. Part 30. Reaction of 5-amino-4,5-dihydro-4-methylene-1,2,3-triazoles with 2,4-diaryl-5-(4H)-oxazolon-4-yl radicals
No full textDetection and mass spectrometric characterization of the major urinary and fecal metabolites of 9-methyl-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]-quinolizine in the rat
No full textThe metabolic fate of 9-methyl 1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinolizine (MIQ), a compound with promising pharmacological action on the CNS system, was investigated in the rat after an oral dose of 200 mg/kg, the maximal tolerated dose. Urine and feces were collected, exhaustively extracted with organic solvents and the metabolites detected by TLC analysis. The structures of the isolated metabolites were characterized by several mass spectrometry techniques (FD, EI, CI) and, in some cases, confirmed by synthesis. The major metabolic pathways of MIQ in the rat involve: C-oxidation of the methyl group in position 9 to a primary alcohol and to a carboxylic acid, N-oxidation of basic nitrogen and C-oxidation of the quinolizidine nucleus, probably at position 7
FIELD DESORPTION MASS-SPECTROMETRY, FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY AND FAST-ATOM-BOMBARDMENT TANDEM MASS-SPECTROMETRY OF ECHINACOSIDE, THE MAIN CAFFEOYL-GLYCOSIDE FROM ECHINACEA-ANGUSTIFOLIA ROOTS (ASTERACEAE)
No full textThe mass spectral fragmentation of echinacoside, a pharmacologically active caffeoyl-glycoside isolated from Echinacea angustifolia roots, has been investigated using different soft-ionization techniques, field desorption and fast atom bombardment (positive and negative ions) mass spectrometry. Both ionization modes are successful in molecular mass determination and furnish approximately equivalent structural information. A fast atom bombardment tandem mass spectrometry approach (negative ions) was developed for the study of the fragmentation pathways and for the detection of echinacoside in crude plant extracts. The results demonstrate the usefulness of this technique for the rapid search of this important caffeoyl-glucoside directly in natural complex matrices
CONFIRMATIVE ASSAY AND QUANTITATIVE-DETERMINATION OF HEDERA-HELIX L SAPONINS (ALPHA-HEDERIN, HEDERACOSIDE-B AND HEDERACOSIDE-C) IN RAW PLANT-EXTRACTS AND IN COSMETIC FORMULATIONS BY EI AND CAD MIKE SPECTROMETRY
No full textAcrolein sequestering ability of the endogenous tripeptide glycyl-histidyl-lysine (GHK) : Characterization of conjugation products by ESI-MSn and theoretical calculations
No full textAcrolein (ACR) is a well-known carbonyl toxin produced by lipid peroxidation of polyunsaturated fatty acids, which is involved in several life-threatening pathologies such as Alzheimer disease, arteriosclerosis, diabetes, and nephropathy. The aim of this work was to study the quenching ability of the endogenous tripeptide glycyl-histidyl-lysine (GHK), a liver cell growth factor isolated from human plasma, towards the electrophilic aldehyde ACR and to characterize the reaction products by electrospray mass spectrometry (ESI-MS/MS infusion experiments; positive ion mode). The reaction of ACR (30 μM) with GHK (0.1, 0.25, 0.5, 1.0 mM) was followed by measuring aldehyde consumption by reverse-phase HPLC (phosphate buffer, pH 7.4); after 4 h, when the aldehyde had completely disappeared; the reaction products were checked by ESI-MS/MS. Several products were detected in the GHK + ACR reaction (1:1). This indicates a complex reaction cascade involving the sequential addition of ACR (up to 3 mol) to the tripeptide GHK and, in particular, to the ε-amino group of the lysine residue and to the Nτ and Nπ of the histidine moiety. The Michael addition of two molecules of ACR to the ε-amino group of the lysine residue is followed by aldol condensation and dehydration to give the N-(3-formyl-3,4-dehydropiperidino) derivative. The results confirm that the ESI-MS/MS approach in a direct infusion experiment permits rapid profiling of the products of the GHK + ACR reaction. They firstly point to the potential medicinal use of GHK in the prevention of carbonyl stress-linked pathologies, and - second - help shed light on the physiological role of this histidine-containing tripeptide which is claimed to be an endogenous growth factor, but has never been shown to be an ACR quencher
v-Triazolines. part XXIII. Cycloaddition reactions of 4-nitrophenylazide to enamines of 1,4,5,6.-tetraphenyl-7-oxo-bicyclo [2.2.1] hept-5-en-2-carboxaldehyde
No full textReacticn of 4-nitrophenylazide with the enamines 5, 6 of 7-oxo-1, 4,5,6-tetraphenylbicyclo [2.2.1]hept-5-en-2-carboxaldehyde 3, 4 which may be isolated or prepared in situ from the aldehyde and the appropriate amine, resulted in the formation of a mixture of three products, namely two diastereoisomeric cycloadducts with the spiro [bicyclo-[2.2.1]hept-2-en-7-one [5.4']1',2',3'-triazole) structure 7 and 8 and rearrangement product of the former with the 5-amino-1-aryl-4-[cyclopent-3-en-1 -one-2-yl]methyl-1,2,3-triazole structure (9). © 1986
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