Structure identification of a prenylflavonol glycoside from Epimedium koreanum by electrospray ionization tandem mass spectrometry

A novel prenylflavonol glycoside, named acetylicariin, has been isolated from the aerial parts of Epimedium koreanum Nakai. The structure has been identified by electrospray ionization multi-stage tandem mass spectrometry (ESI-MSn) and other chemical evidence, which has been elucidated as 8-prenylkaempferol-4'-methoxyl-3-O-alpha-L-rhamnopyranosyl-7-O-beta-D-(2''-O-acetyl)glucopyranoside.

Analysis of norditerpenoid alkaloids extracted from Aconitum sinomantanum Nakai by electrospray ionization tandem mass spectrometry

Electrospray ionization mass spectrometry (ESI-MS) was applied simultaneously in determining norditerpenoid alkaloids from the roots of Aconitum sinomantanum Nakai ( RAS) based on molecular mass information. The tandem mass spectra (ESI-MSn) provided the alkaloidal structural information, through which the existence of these alkaloids was further confirmed. Accordingly, six known norditerpenoid alkaloids were simultaneously determined on the basis of their ESI-MSn spectra. Furthermore, based on the diagnostic fragmentation pathways of alkaloidal MSn, a rapid method for direct detection and characterization of alkaloids from an ethanolic extract of RAS was described.

Detection and characterization of non-covalent complex between lappaconitine and beta-cyclodextrin by electrospray ionization tandem mass spectrometry

The non-covalent complexes between lappaconitine (LA) and beta-cyclodextrin (beta-CD) have been detected and characterized by electrospray ionization combined with ion trap tandem mass spectrometry (ESI-MSn). The experimental results showed that only 1:1 non-covalent complex can be formed in different starting molar ratios of LA to beta-CD. Furthermore, the diagnostic fragmentation of the beta-CD-LA complex, with a significant contribution of covalent fragmentation of LA leaving the N-acetyl anthranoyl (AN) moiety inserted to beta-CD, provided the convincing evidence for the formation of non-covalent complex between LA and beta-CD and the cite of LA molecule included to cavity of beta-CD assigned to AN residue.

Exploring the ester-exchange reactions of diester-diterpenoid alkaloids in the aconite decoction process by electrospray ionization tandem mass spectrometry

The chemical components in the decoctions of Chinese herbal medicines are not always the same as those in the crude herbs because of the insolubility or instability of some compounds. In this work electrospray ionization tandem mass spectrometry was used to explore the ester-exchange reactions for aconitine-type diester-diterpenoid alkaloids occurring during the process of decocting aconite root. The aconitines were screened in a diverse range of samples, including crude aconite, decoction of crude aconite, residues from decoction of crude aconite, prepared aconite, decoction of prepared aconite, decoction of prepared aconite with added palmitic acid, and decoction of a mixture of mesaconitine and hypaconitine standards with liquorice root. It was found that diester-diterpenoid aconitines were converted into lipo-alkaloids as well as monoester alkaloids by the decoction of aconite.

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.

Structure identification of five unknown dilipo-alkaloids extracted from processed tuber of Aconitum carmiechaeli by electrospray ionization tandem mass spectrometry

The alkaloids in processed aconite tuber of Aconitum Carmiechaeli were studied, and five novel alkaloids in extract from processed aconite tuber were found. The first step involved the use of electrospray ionization mass spectrometry (ESI-MS), and then multi-stage tandem mass spectrometry (MSn) was used to provide structural information. Based on their MSn spectra, the structures of the five novel compounds were elucidated to be C3,C8-difatty acid esters of mesaconitine, aconitine and 10-hydroxyaconitine.

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.

Electrospray ionization tandem mass spectrometric study of the aconitines in the roots of aconite

Fragmentation pathways of aconitine-type alkaloids were investigated by electrospray ionization/ion trap multistage tandem mass spectrometry. Low-energy collision-induced dissociation of protonated aconitines follows a dominant first step, the elimination of the C-8-substituent as acetic acid or fatty acid in MS2 spectra. Successive losses of 1-4 CH3OH molecules, 1-3 H2O, CO, benzoic acid, and CH3 or C2H5 (N-substituents) are all fragmentation pathways observed in MS3 and MS4 spectra. By applying knowledge of these fragmentation pathways to the aconitines in the ethanolic extract of aconite roots, all the known aconitines were detected and also 23 unknown aconitine-type alkaloids, in which the lipo-alkaloids containing residues of 15C, 17C and 19C saturated or unsaturated fatty acids were characterized. These odd-carbon-number fatty acid substituents have not been reported previously.

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.

Gaseous dipeptide complexes with metal ions by electrospray ionization and tandem mass spectrometry

Electrospray ionization (ESI) and tandem mass spectrometry have been used to investigate the gas-phase interactions of five metal ions and seven dipeptides. For silver ion, two complexes ([M+Ag](+) and [2M+Ag](+)) were obtained as well as the one complex ([2M+Met-H](+)) for transition-metal ions. Upon collision activation, there is an obvious difference in MS/MS data between metal ion complex and the protonated molecule. The fragment pathway of each complex is related to the structures of dipeptide and the nature of metal ion which suggest that there are several interaction between the metal ions and dipeptides in gas phase.

Studies on negative electrospray ionization mass spectrometry on saponins

Two kinds of saponins have been investigated by negative electrospray ionization (NESI) mass spectrometry. Under ESI conditions, the [M - H](-) ions of saponins were observed which provide the molecular weights of saponins. The fragment pathways of [M - H](-) ions of these two saponins depend on their structures. For steroidic saponins, [M - H](-) ion only produces the fragment ions by the losses of sugar units. For oleanolic saponins, [M - H](-) ion yields the cross-ring ions as well as the fragment ions by the losses of sugar units. Moreover, the abundance of the former is higher than that of the latter. The characteristic fragments are used to provide the sequence and some linkage information of sugar moieties of saponins. Especially, their fragment difference strongly depends on the linkage between the aglycone and the sugar moieties.

Investigation of metalloporphyrins and their imidazole complexes using electrospray ionization mass spectrometry

Three compounds of metalloporphyrins were studied using electrospray ionization mass spectrometry. The bonding power between substitutional phenyl and porphyrin cycle and the coordinate conditions of metalloporphyrins with imidazole were discussed. The experimental result indicated that the bonding power between substitutional phenyl and porphyrin cycle in metalloporphyrins became weak from Mn, Fe to Co. The complexes abundances formed by metallophorphyrin with imidazole were stronger with the increase of the ligand concentration. At the same ligand concentration, the abundance of the complexes was intensified gradually and the stability of the ligands was become stronger from Mn, Fe to Co.

Metal ion adducts in the structural analysis of ginsenosides by electrospray ionization with multi-stage mass spectrometry

The effect of metal (Li+, Na+, K+, Ag+) cationization on collision-induced dissociation of ginsenosides was investigated by electrospray ionization mass spectrometry combined with multi-stage mass spectrometry (ESI-MSn). The fragments of sodiated and lithiated molecules give valuable structural information regarding the nature of the aglycone and the sequence and linkage information of sugar moieties. However, the number and relative abundances of fragment ions from lithiated ginsenosides are significantly greater than for the sodiated species, The K+ adducts undergo glycosidic cleavages and very limited cross-ring reactions. The silver ion adducts fragment mainly through glycosidic cleavages. Copyright (C) 2001 John Wiley & Sons, Ltd.

Electrospray ionization multiple-stage tandem mass spectrometric analysis of diglycosyldiacylglycerol glycolipids from the bacteria Bacillus pumilus

Electrospray ionization (ESI) combined with multiple-stage tandem mass spectrometry (MSn) was used to directly analyze the glycolipid mixture from bacteria Bacillus pumilus without preliminary separation. Full scan ESI-MS revealed the composition of picomole quantities of glycerolglycolipid species containing C-14-C-19 fatty acids, some of which were monounsaturated, Two main components were identified from their molecular masses and fragmentation pathways. The fragmentation pathway of the known compound compared with the investigated compound verified the proposed structure as 1(3)-acyl-2-pentadecanoyl-3(1)-O-[beta-D-glucopyranosyl-(1-->6)-O-beta-D-glucopyranosyl]-sn-glycerols. A comparison of the multiple tandem mass spectra of the different alkali-metal cation adducts indicates that the intensity of fragments and the dissociation pathways are dependent on the alkali-metal type, The basic structures of glycerolglycolipids were reflected clearly from the fragmentation patterns of the sodium cations, The intense fragments of the sugar residue from the precursor ions were obtained from the lithiated adduct ions. ESI-MSn spectra of [M + K](+) ions did not provide as much fragmentation as [M + Na](+) and [M + Li](+) adducts, but their spectra allow the position of glycerol acylation to be determined. On the basis of MS2 spectra of[M + K](+) ions, it was established that all components have a C-15:0 fatty acid at the sn-2 position of the glycerol backbone and C-14-C-19 acids at the sn-1 position of the glycerol backbone. Copyright (C) 1999 John Wiley & Sons, Ltd.