Analysis of two trace alkaloid isomers in Strychnos nux-vomical by electrospray ionization tandem mass spectrometry

According to their molecular mass and ESI-MSn data, the trace alkaloid isomers pseudostrychnine and strychnine N-oxide in extracts of the total alkaloids from Strychnos nux-vomical were qualitatively analyzed by electrospray ionization tandem mass spectrometry (ESI-MSn) method after rough silica gel-column chromatographic separation. We also investigated the relationship between their fragmentation mechanism and structures of the two alkaloid isomers. A new method for quickly and highly sensitively analyzing the two alkaloid isomers was proposed.

Characterization of the rutin-metal complex by electrospray ionization tandem mass spectrometry

According to the strong application background of bioflavonoid and metal-flavonoid complexes, novel electrospray ionization tandem mass spectrometry (ESI-MSn) was applied to investigate the structure and fragmentation mechanism of transition metal-rutin complexes. In the full-scan mass spectra, different stoichiometric ratios of rutin-metal complexes were found. In the reaction between rutin and Cu, four kinds of complexes with four different stoichiometric ratios were produced. In the reaction between rutin and Zn, Mn(II), and Fe(II), only two kind of complexes with stoichiometric ratios of 1:1 and 1:2 occured. In further tandem mass spectrometric experiments of different rutin-metal complexes, product fragments, came from the neutral loss of the external rhamnose and the internal glucose unit, oligosaccharide chain, aglycone, and small organic molecules. According to the MSn data, we proposed a mechanism for all fragments of the rutin-Cu complex A and the structure of two rutin-Cu complexes, C and D.

Studies on the flavones using liquid chromatography-electrospray ionization tandem mass spectrometry

Fragmentation pathways of nine flavone compounds have been studied by using electrospray ionization multi-stage tandem mass spectrometry (ESI-MSn). Analyzing the product ion spectra of flavonoids and aglycones, we observed some diagnostic neutral losses, such as *CH3, H2O, residue of glucose and gluconic acid, which are very useful for the identification of the functional groups in the structures. Furthermore, specific retro Diels-Alder (RDA) fragments for flavones with different hydroxyl substitution have also been discussed. The information is helpful for the rapid identification of the location site of hydroxyl substitution on flavones. Fragmentation pathways of C-glycosidic flavonoid have also been discussed using ESI-MSn, demonstrating ions [M-H-60](-), [M-H-90](-), [M-H-120](-) are characteristic ions of C-glycosidic flavonoid. According to the fragmentation mechanism of mass spectrometry and HPLC-MS data, the structures of seven flavones in Scutellaria baicalensis Georgi have been identified on-line without time-consuming isolation. The HPLC-ESI-MSn method for analyzing constituents in the Scutellaria baicalensis Georgi has been established.

Characterization of non-covalent complexes of rutin with cyclodextrins by electrospray ionization tandem mass spectrometry

Electrospray ionization tandem mass spectrometry (ESI-MSn) and the phase solubility method were used to characterize the gas-phase and solution-phase non-covalent complexes between rutin (R) and alpha-, beta- and gamma-cyclodextrins (CDs). The direct correlation between mass spectrometric results and solution-phase behavior is thus revealed. The order of the 1:1 association constants (K-c) of the complexes between R and the three CDs in solution calculated from solubility diagrams is in good agreement with the order of their relative peak intensities and relative collision-induced dissociation (CID) energies of the complexes under the same ESI-MSn condition in both the positive and negative ion modes. Not only the binding stoichiometry but also the relative stabilities and even binding sites of the CD-R complexes can be elucidated by ESI-MSn. The diagnostic fragmentation of CD-R complexes, with a significant contribution of covalent fragmentation of rutin leaving the quercetin (Q) moiety attached to the CDs, provides convincing evidence for the formation of inclusion complexes between R and CDs. The diagnostic fragment ions can be partly confirmed by the complexes between Q and CDs. The gas-phase stability order of the deprotonated CD-R complexes is beta-CD-R > alpha-CD-R > gamma-CD/R; beta-CD seems to bind R more strongly than the other CDs.

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-MSn). 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-MSn has been proven to be an effective tool for rapid determination of native saponins in extract mixtures, thus avoiding tedious derivatization and separation steps.

Analysis of strychnos alkaloids using electrospray ionization Fourier transform ion cyclotron resonance multi-stage tandem mass spectrometry

The fragmentations of four strychnos alkaloids have been investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) in the positive ion mode. Experiments using multi-stage tandem mass spectrometry (ESI-FT-ICR-MSn) allowed us to obtain precise elemental compositions of product ions at high mass resolution. The experimental data demonstrated that the nitrogen bridge and the coordinated oxygen atom on the nitrogen bridge in the alkaloid compounds were the active sites in the MS2 fragmentations. The loss of CH3 or the OCH3 group in those alkaloids, which have an OCH3 substituent, was the dominant fragmentation mode in the MS3 fragmentations. Logical fragmentation schemes for strychnos alkaloids have been proposed and these should be useful for the identification of these compounds.

Characterization of aconitine-type alkaloids in the flowers of Aconitum kusnezoffii by electrospray ionization tandem mass spectrometry

The fragmentation mechanism of aconitine-type alkaloids in the flowers of Aconitum kusnezoffii (FAK) was investigated using electrospray ionization tandem mass spectrometry (ESI-MSn) firstly. The analysis of the collision-induced dissociation (CID) spectra of three purified aconitine standards and six previously reported aconitines indicated that the fragmentation of the protonated aconitines at low-energy CID follows a similar pathway. The elimination of a C-8-substituent such as an acetic acid or a fatty acid is the dominant fragmentation mode in MS2. Successive losses of CH3COOH, CH3OH, H2O, BzOH, and CO are the main fragmentation pathways of aconitine-type alkaloids in MS3 spectra. Based on these features, a rapid method for the direct detection and characterization of alkaloids from an ethanolic extract of FAK is described. All the known aconitum alkaloids are detected and a series of lipo-aconitines has been found for the first time in this plant.

Studies on the non-covalent complexes between oleanolic acid and cyclodextrins using electrospray ionization tandem mass spectrometry

Non-covalent inclusion complexes formed between an anti-inflammatory drug, oleanolic acid (OA), and alpha-, beta- and gamma-cyclodextrins (CDs) were investigated by means of solubility studies and electrospray ionization tandem mass spectrometry (ESI-MSn). The order of calculated association constants (K-1:1) of complexes between OA and different CDs in solution is in good agreement with the order of their relative peak intensities and the relative CID energies of the complexes under the same ESI-MSn conditions. These results indicate a direct correlation between the behaviors of solution- and gas-phase complexes. ESI-MS can thus be used to evaluate solution-phase non-covalent complexes successfully. The experimental results show that the most stable 1:1 inclusion complexes between three CDs and OA can be formed, but 2:1 CD-OA complexes can be formed with beta- and gamma-CDs. Multi-component complexes of alpha-CD-OA-beta-CD (1:1:1), alpha-CD-OA-gamma-CD (1:1:1) and beta-CD-OA-gamma-CD (1:1:1) were found in equimolar CD mixtures with excess OA. The formation of 2:1 and multi-component 1:1:1 non-covalent CD-OA complexes indicates that beta- and gamma-CD are able to form sandwich-type inclusion non-covalent complexes with OA. The above results can be partly supported by the relative sizes of OA and CD cavities by molecular modeling calculations.

Rapid molecular weight determination of recombinant hirudin by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The molecular weight of recombinant hirudin ( rHV-2) was determined rapidly by matrix-assisted laser desorption/ionization time of fight mass spectrometry (MALDI-TOF-MS). The effects of the three types of matrixes were compared and discussed, alpha-cynao-4-hydroxycinnamic acid was proved to be the best matrix. It showed that MALDI-TOF-MS was superior to the traditional method of molecular weight determination of the biological macromolecules. The mass spectrum data proved that the primary structure of rHV-2 was correct and there was no amino acid deletion, mutation and modification in its expression, refolding and purification.

Analysis of chemical constituents of essential oil in purple magnolia leaves by gas chromatography-mass spectrometry

The essential oil in purple magnolia leaves was extracted by steam distillation approaches. The oil obtained was dried with anhydrous magnesium sulfate. According to the analysis of gas chromatography/mass spectrometry, more than 40 peaks were separated and 32 compounds were identified. The identified constituents represent 95% of the peak area of the essential oil. The main compounds were germacrene-D, santolina triene, caryophyllene, 1,3,7-octatriene, 3,7-dimethyl, and camphene, etc.

Rapid identification of saponins in plant extracts by electrospray ionization multi-stage tandem mass spectrometry and liquid chromatography/tandem mass spectrometry

Electrospray ionization multi-stage tandem mass spectrometry (ESI-MSn) and liquid chromatography coupled with on-line mass spectrometry (LC/MS/MS) were applied to characterize saponins in crude extracts from Panax ginseng. The MSn data of the [M - H](-) ions of saponins can provide structural information on the sugar sequences of the saccharide chains and on the sapogins of saponins. By ESI-MSn, non-isomeric saponins and isomeric saponins with different aglycones can be determined rapidly in plant extracts. LC/MS/MS is a good complementary analytical tool for determination of isomeric saponins. These approaches constitute powerful analytical tools far rapid screening and structural assignment of saponins in plant extracts. Copyright (C) 2000 John Wiley & Sons, Ltd.

Mass spectrometry study on snake venoms and enzymes

In this paper, three kinds of snake venoms and lour kinds of enzymes (phospholipase A(2), fibrinolytic enzyme, arginine esterase and L-amino acid oxidase) isolated from the snake venom were analyzed. As the snake venom was different, the MALDI/TOF/MS showed difference, The MALDI/TOF/MS determination results could be affected Ly the concentrations of snake venom enzymes, And the mechanisms of desorption and ionization was also given in this study, By using MALDI/TOF/MS we obtained the accurate molecular weights and homogeneities of the enzymes. The apparent characteristics of the positive MALDI/TOF/MS of enzymes composed by two subunits were also given out, The results showed that MALDI/TOF/MS is an effective analytic method for discovering new components from snake venom complexes. And it is reliable to use this method to determine the molecular weights and purifies of protein molecules.

Analysis of poly (arylene phosphonate) cyclic oligomer by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MAIDI-TOF-MS) was used for analysis of poly(arylene phosphonate) cyclic oligomers. A comparison was made by using 1,8,9-dithranol, 2,5-dihydroxybenzoic acid and retinoic acid as the matrix. The result showed that the retinoic acid produced the strongest ion signals under the conditions used. Different salts of metals were used as the cationization agents to examine the effect on the cyclic oligomers. It was found that the salts could produce metal-cyclic oligomer cation spectra and lithium was the stronger one than those of silver so, the suitable matrix and cationization agent for the new cyclic oligmer were obtained. They were very effective for the analysis of poly(arylene phosphonate) cyclic oligomer.

Investigation of a series of synthetic cationic porphyrins using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used to study a series of synthetic cationic porphyrins as the perchlorate and bromide salts. This work presents the analytical results for the porphyrins obtained using 2,5-dihydroxybenzoic acid (DHB) and 1,8,9-anthratriol as matrices. The selective use of matrix affects ion formation from these porphyrins. By using DHB as the matrix, we not only observed [M - nCIO(4)](+) (n = 1-4) ions, but also obtained [2M - nCIO(4)](+) (n = 2-7) ions from the synthetic cationic porphyrins. The space volume of the side chains (R groups) and the nature of the anions (Br- or CIO4-) affected the relative importance of monomeric and dimeric ions of the porphyrin. The possible mechanisms of desorption and ionization of these cationic porphyrins were also considered in this study. MALDI-TOFMS proved to be a very useful method for obtaining structural information on these synthetic cationic porphyrins. Copyright (C) 1999 John Whey & Sons, Ltd.