Hydroxycinnamoylmalated flavone C-glycosides from Lemna japonica.

Three previously undescribed flavone C-glycosides (1-3), along with seven known ones (4-10), were isolated and characterized from the smallest flowering aquatic plant, Lemna japonica. On the basis of spectroscopic analysis and alkaline hydrolysis, compounds 1-3 were identified to be luteolin 6-C-(2″-O-trans-caffeoyl-d-malate)-ß-glucoside (1), apigenin 6-C-(2″-O-trans-caffeoyl-d-malate)-ß-glucoside (2), and luteolin 6-C-(2″-O-trans-coumaroyl-d-malate)-ß-glucoside (3). Compounds 1-3 are characteristic of a trans-coumaroyl-d-malate or trans-caffeoyl-d-malate linked to C-2″ of the glucose, which was reported for the first time. Compounds 1-3 exhibited weak cytotoxicity against HepG-2, SW-620, and A-549 cell lines, with IC50 values between 42.5 and 19.2µg/ml, and moderate antioxidant activity. Meanwhile compound 3 displayed moderate nematocidal activity with an EC50 value of 1.56mg/ml.

Cytotoxic triterpenoid saponins from Clematis tangutica.

Eight previously undescribed oleanane-type triterpenoid saponins, clematangoticosides A-H, together with eight known saponins, were isolated from the whole plants of Clematis tangutica (Maxim.) Korsh. Their structures were elucidated by extensive spectroscopic analysis, in combination with chemical methods (acid hydrolysis and mild alkaline hydrolysis). Clematangoticosides D-G were found to be unusual 23, 28-bidesmosidic glycosides. The cytotoxic activities of all of the isolated saponins were evaluated against the four human cancer cell lines SGC-7901, HepG2, HL-60 and U251MG. Clematoside S, sapindoside B, kalopanax saponin A, and koelreuteria saponin A exhibited cytotoxicity against all of the test cancer cell lines with IC50 values in the range of 1.88-27.20 µM, while clematangoticoside D and F showed selective cytotoxicity against SGC-7901 with IC50 values of 24.22 and 21.35 µM, respectively.

[Chemical Constituents from Przewalskia tangutica].

Objective: To study the Chemical constituents from Przewalskia tangutica. Methods: The compounds were isolated and identified from n-butanol extract of Przewalskia tangutica by various chromatographic and spectral techniques. Results: Twelve polar compounds were isolated and identified as scopolin( 1),fabiatrin( 2),rutin( 3),queroetin-3-O-rutinoside-7-O-ß-D-glucopyranoside( 4),protocatechuate( 5),vanillic acid( 6),thymine( 7),uracil( 8),cytosine( 9),adenine( 10),uridine( 11) and adenosine( 12). Conclusion: Compounds 3 ~ 5,8 ~ 12 are obtained from Przewalskia tangutica for the first time.

Evaluation of relative isotopic abundance measurements in a quadrupole time-of-flight mass spectrometer for elemental composition determination of natural products in traditional Chinese medicine.

The relative isotopic abundance (RIA) measurement errors of a quadrupole time-of-flight (Q-ToF) instrument incorporating analog-to-digital converter detectors were systemically evaluated by stochastically collecting about 200 data in positive ion mass spectrometry (MS) mode. Errors varied with peak intensities at definite spectral acquisition rates but were very close, even if peak intensities changed sharply at different spectral acquisition rates with the same concentration. Intensity thresholds were systematically defined at 1 Hz of spectral acquisition rates. RIA measurement errors were also evaluated using peak area. It seemed that peak area was better adapted for the high-intensity ions while peak intensity was suited for very low-intensity ions. Several known compounds were selected for RIA measurements for product ions in tandem mass spectropmetry (MS/MS) mode. An extract of a representative traditional Chinese medicinal, Paederia scandens was analyzed with high-performance liquid chromatography-electrospray ionization-QToF-MS/MS. The unique elemental compositions of some compounds could not be identified even with exact masses and MS/MS spectra of measured and reference compounds. RIA errors, especially of (M+2)M(-1), provided vital information for determining the elemental composition.

Analysis of mexicanolide- and phragmalin-type limonoids from Heynea trijuga using high-performance liquid chromatography/electrospray tandem mass spectrometry.

RATIONALE: Limonoids, a class of tetranortriterpenoids, exhibit various biological effects, including acting as potent antifeedants and insect growth-regulators against various pests. The analysis of phragmalin- and mexicanolide-type limonoids by collision-induced dissociation tandem mass spectrometry (CID-MS/MS) has not been reported. METHODS: A high-performance liquid chromatography/electrospray ionization (HPLC/ESI)-MS/MS method was developed to investigate the fragmentation patterns of [M+NH4 ](+) ions for nine reference phragmalin- and mexicanolide-type limonoids. The method was also used in the identification of limonoid compounds in botanic extracts of Heynea trijuga. RESULTS: The losses of side chains and the furan part were the major fragmentation patterns. However, there was variation in the relative abundances of product ions resulting from the same fragmentation pathways. A total of 89 phragmalin- and mexicanolide-type limonoids in botanic extracts of Heynea trijuga were detected and 50 of these compounds were identified or tentatively characterized based on elemental constituents, fragmentation pathways, and the profile of the major product ions of reference compounds. In addition, the isomers could be tentatively distinguished. CONCLUSIONS: An HPLC/ESI-MS/MS method was developed and could be used to simultaneously identify and screen phragmalin- and mexicanolide-type limonoids in botanic extracts of Heynea trijuga.

Analysis of iridoid glucosides from Paederia scandens using HPLC-ESI-MS/MS.

Iridoid glycosides are an important class of natural products and have many biological activities. Iridoid glucosides in an extract of the plant species Paederia scandens were investigated using reversed-phase high performance liquid chromatography and electrospray quadrupole time-of-flight-type tandem mass spectrometry. The elemental composition of most of the compounds was determined by accurate mass and relative isotopic abundance (RIA) measurements. In positive ion mode, the fragmentation of [M+NH4](+) precursor ions was carried out using low energy collision-induced electrospray ionization tandem spectrometry. The neutral losses of NH3, H2O, Glc, and the side chain of the iridoid moiety were the main fragmentation patterns observed. For simple iridoid glycosides, the main differences were related to the side chains. Fragmentation of the [M-H](-)precursor ions was achieved for the compounds possibly having phenolic acid group. The connection order of the iridoid, sugar, and phenolic acid moieties, and the linkage of the 6-OH group of the sugar to the phenolic acid were unambiguously confirmed using a combination of MS/MS spectra in both positive and negative ion modes, and our previous work. For some trace dimeric iridoid glucosides, the connection order between the asperuloside and paederoside moieties was determined by the characteristic product ions; this was supported by D-labeling experiments. A total of 24 iridoid glucosides, including 14 new species, were identified or tentatively characterized based on exact mass, RIA values, tandem mass spectra, and D-labeling experiments.

Analyses of the iridoid glucoside dimers in Paederia scandens using HPLC-ESI-MS/MS.

INTRODUCTION: Many dimers consisting of structurally similar monomers are difficult to be identified even using NMR. Rapid structural identification of iridoid glycoside dimers, especially isomeric dimers in a complicated matrix, remains desirable. OBJECTIVE: To develop a rapid, sensitive analytical method for structural elucidation of trace iridoid glycoside isomers in a complicated extract. METHODS: Three isomeric iridoid glucoside dimers, paederoscandoside, saprosmoside E and saprosmoside D, were isolated and further analysed by electrospray ionisation quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) in positive-ion mode. Energy-resolved mass spectrometry (ERMS) was used to provide information on the relative intensity of ions versus collision energy. The crude extract of Paederia scandens was analysed by HPLC-ESI-MS/MS. RESULTS: The relative abundance of product ions in the MS/MS spectra from ammonium adduct ions varied greatly for the three isomers. The energy-resolved experiments enhanced differences among the three isomers. A total of 13 iridoid glucoside dimers (three groups of isomers) in the extract of P. scandens were identified or tentatively characterised by using HPLC-ESI-QTOF based on the tandem mass spectra of references. CONCLUSION: Linkage sites between different hydroxyl groups on the sugar and carboxyl groups for the three groups of isomers are confirmed. The reason for fragmentation differences might be that cleavage of the glycosidic bond accompanies the active H in vicinal hydroxyl rearrangement. The MS method is a useful tool for the analysis of isomers, especially trace isomers in a complicated extract.

Electrospray tandem mass spectrometry of epipolythiodioxopiperazines.

Low-energy collision-induced electrospray ionization tandem mass spectrometry ESI-CID-MS/MS (in the positive ion mode) was used for the structural characterization of a series of five representative epioplythiodioxopipreazines: dethiotetra(methylthio)chemotin, chaetocochins A, B and C, and chemotin isolated from the fungus Chaetomium cochliodes. The fragmentation pathways were elucidated by ESI-IT-MS(n). The elemental compositions of most of the product ions were confirmed by low-energy ESI-CID-QTOF-MS/MS analyses. The loss of the S(2) molecule seems always to be the first when the S--S bond is present. The loss of 77 Da corresponding to the loss of the [CH(3)SCH(2)O]' radical was diagnostic for chaetocochins A and B, in which the two piperazines rings are linked by an acetal group. It was found that a McLafferty rearrangement plays a significant role in the skeleton fragmentation of theses series of studied complex multicyclic piperazine compounds. This MacLafferty rearrangement affords the product ions at m/z 416 and 400, containing the two piperazine rings belonging to the epipolythiodioxopipreazines. In addition, the pentacyclic rearrangement involving the loss of the SMe(.) radical seems to occur in the presence of the unfused ring. Finally the product ions at m/z 635 and 591 seem to be the characteristic ions for chaetocochin A.