Desorption/Chemical Ionization Mass Spectrometry of Naturally Occurring Glycosides

Mass Spectrometric Identification of Metabolites after Magnetic-Pulse Treatment of Infected Pyrus communis L. Microplants

The major goal of this study is to create a venue for further work on the effect of pulsed magnetic fields on plant metabolism. It deals with metabolite synthesis in the aforementioned conditions in microplants of Pyrus communis L. So far, there have been glimpses into the governing factors of plant biochemistry in vivo, and low-frequency pulsed magnestatic fields have been shown to induce additional electric currents in plant tissues, thus perturbing the value of cell membrane potential and causing the biosynthesis of new metabolites. In this study, sixty-seven metabolites synthesized in microplants within 3-72 h after treatment were identified and annotated. In total, thirty-one metabolites were produced. Magnetic-pulse treatment caused an 8.75-fold increase in the concentration of chlorogenic acid (RT = 8.33 ± 0.0197 min) in tissues and the perturbation of phenolic composition. Aucubin, which has antiviral and antistress biological activity, was identified as well. This study sheds light on the effect of magnetic fields on the biochemistry of low-molecular-weight metabolites of pear plants in vitro, thus providing in-depth metabolite analysis under optimized synthetic conditions. This study utilized high-resolution gas chromatography-mass spectrometry, metabolomics methods, stochastic dynamics mass spectrometry, quantum chemistry, and chemometrics, respectively. Stochastic dynamics uses the relationships between measurands and molecular structures of silylated carbohydrates, showing virtually identical mass spectra and comparable chemometrics parameters.

Analysis of Saponin Mixtures from Alfalfa (Medicago Sativa L.) Roots using Mass Spectrometry with MALDI Techniques

This model study demonstrates the value of Matrix Assisted Laser Desorption Ionization (MALDI) MS in global analysis of mixtures of saponin isolates. Unfractionated saponin extract derived from alfalfa [Medicago sativa L.] roots was analyzed. In addition, a few saponin fractions that were purified from the same extract by a series of chromatographic steps were also studied. MALDI mass spectrometry utilized TOF, TOF/TOF and QqTOF analyzers. Low-resolution fingerprints of the mixture characterized the sample in terms of a minimal number of distinct saponin components. The main species observed under MALDI-TOF and oMaldi-QqTOF MS positive ion mode conditions were sodiated pseudomolecular ions [M+Na]+. No protonated molecular ions [M+H]+ were detected. The MS/MS spectra acquired on [M+Na]+ precursor ions under conditions of collision induced dissociation (CID) were dominated by cleavages at glycosidic bonds. Product ions representing free aglycones were either absent or present at low intensities and were never observed for structures carrying an oligosaccharide bound to a sapogenin at the C3- O-position. In general, product ion series generated from CID fragmentation of glycans bound via an ether bond ( e.g., C3- O-position in medicagenic acid) were consistent with the gas phase cleavages of each of the glycosidic bonds within the oligosaccharide, thus revealing the primary structure. In contrast, glycans bound via an ester bond ( e.g., C28- O-position in MA) were released as intact sodiated species. A total of 78 pseudomolecular ions demonstrating signal-to-noise ratios above 5 were observed in the MALDI-TOF mass spectrum of unfractionated root extract from M. sativa. Molecular masses of 52 out of 78 were consistent with at least one known or novel saponin structure, with 10 of those 52 likely representing doubly sodiated saponin species. Calculated masses of the majority of the known M. sativa saponin structures were matched to experimental pseudomolecular ion masses. MS/MS analysis of unfractionated extract allowed us to propose putative structures for 51 saponins: 15 of these corresponded to the known M. sativa species, 8 to other Medicago genus species and 26 were not reported before for Medicago genus. We submit that the approach described here might serve as a high throughput strategy for evaluating effects of stressors or genetic manipulation on the overall composition of the saponin content of an organism.

Structural analysis of saponins from medicinal herbs using electrospray ionization tandem mass spectrometry

The underivatized saponins from Tribulus terrestris and Panax ginseng have been investigated by electrospray ionization multi-stage tandem mass spectrometry (ESI-MS(n)). In ESI-MS spectra, a predominant [M + Na](+) ion in positive mode and [M - H](-) ion in negative mode were observed for molecular mass information. Multi-stage tandem mass spectrometry of the molecular ions was used for detailed structural analysis. Fragment ions from glycoside cleavage can provide information on the mass of aglycone and the primary sequence and branching of oligosaccharide chains in terms of classes of monosaccharides. Fragment ions from cross-ring cleavages of sugar residues can give some information about the linkages between sugar residues. It was found that different alkali metal-cationized adducts with saponins have different degrees of fragmentation, which may originate from the different affinity of a saponin with each alkali metal in the gas phase. ESI-MS(n) has been proven to be an effective tool for rapid determination of native saponins in extract mixtures, thus avoiding tedious derivatization and separation steps.

Laser desorption/fourier transform ion cyclotron resonance mass spectrometry: digoxin, digitoxin, and their reduced and sugar-hydrolyzed metabolites

Mass spectra of digoxin and digitoxin (the most widely prescribed drugs for treatment of congestive heart failure) and a complete set of their 14 dihydro- and sugar-hydrolyzed metabolites have been obtained via laser desorption/ionization with a Fourier transform ion cyclotron resonance (LD/FT/ICR) mass spectrometer. The most intense peak is typically the pseudomolecular [M + K]+ ion, but fragment ions corresponding to loss of 1-3 sugars and hydroxyls are also observed. LD/FT/ICR mass spectra for all 16 compounds were produced with a single set of sample and spectrometer parameters. No matrix peaks are present. Finally, LD/FT/ICR provides dynamic mass accuracy within approximately 5 ppm throughout a mass range of 404 less than m/z less than 819.

Fast atom bombardment and tandem mass spectrometry for structure determination of steroid and flavonoid glycosides

The combination of fast atom bombardment (FAB) and tandem mass spectrometry (MS-MS) was tested for its applicability to generate useful structural information for steroid and flavonoid glycosides. The following compounds were investigated: quercetin, myricitrin, apigetrin, fraxin, rutin, neohesperidin, hesperidin, naringin, apiin, cymarin, digoxin, digitoxin, xanthorhamnin, and frangulin. Upon FAB, the sample molecules are desorbed as (M + H)+, (M - H)-, or as (M + Na)+ or (M + K)+. Collisional activation of (M + H)+ or (M - H)- ions in the MS-MS experiment leads to sequential losses of glycoside moieties in a manner which permits the sequence of glycosides to be established. Some glycosides occur as mixtures of homologs. Proper interpretation of the MS-MS or collisional activation decomposition spectra often allows the homology to be located. In addition to the simple and highly selective fragmentations observed in this combined experiment, FAB and MS-MS also remove interference caused by the ubiquitous matrix ions which are desorbed by FAB.

Systematic analysis of desorption chemical ionization (DCI) mass spectra of nucleic acids--7

The positive ion and negative ion pyrolysis mass spectra of the herring sperm DNA have been studied using desorption chemical ionization. The positive ion desorption chemical ionization spectra have been produced with CH4, i-C4H10, NH3, HCl and Cl2; the negative ones with N2O/CH4, N2O/i-C4H10, Cl2, CCl4, HCl and via electron capture. These spectra have been compared with the electron impact ionization spectra. We have observed an important increase of sensitivity when negative ionization has replaced the positive ionization mode. The series of diagnostic ions resulting from direct chemical ionization belong to the family of base + reagent ion X [BH + X] and base + X - HX ion [B]. Their abundance has increased considerably compared to the electron impact spectra. The application of these new diagnostic ions in nucleic acid studies is interesting especially for the much higher abundance of the usually weak dG fragment ion obtained in the negative ionization mode. The dG-base segment of the DNA is the most nucleophilic centre of the whole nucleic acid and is implicated in numerous important biochemical reactions involving, for example, proteins.

Isolation and structural elucidation of an ichthyocrinotoxin from the smooth trunkfish (Lactophrys triqueter Linnaeus)

An ichthyocrinotoxin has been isolated from the skin secretion of the smooth trunkfish, Lactophrys triqueter Linnaeus (family Ostraciidae). A crystalline toxin was isolated and identified as the choline chloride ester of palmitic acid. The toxin has a minimum lethal concentration of 2 ppm and an LC50 of 3.5 ppm using mosquito fish as the test organism. A trace quantity of the choline ester chloride of heptadecanoic acid was identified as a minor component of the toxin.