Analysis of oxovanadium(IV) complexes using electrospray mass spectrometry: Molecular ion formed by loss of an electron, and its product ions trapping oxygen.

RATIONALE: In addition to their biological properties, oxovanadium complexes have been widely applied as catalysts because of their excellent catalytic-oxidation capability. Recently, monometallic oxovanadium(IV) complexes have been used as catalysts in the electrophilic trifluoromethylation of silyl ketene imines. The study of catalysts can contribute to an understanding of the reaction mechanism. METHODS: Six monometallic oxovanadium(IV) complexes were analyzed by electrospray ionization time-of flight mass spectrometry (ESI-TOFMS), and collision-induced dissociation mass spectrometry (CID-MS) experiments were conducted for selected cations [M]+ of oxovanadium(IV) complexes as well as a deuterium-labeled complex. Different collision gases were used to understand the source of the O2 and H2 O engaged in the gas-phase ion-molecule reaction. RESULTS: The oxovanadium(IV) complexes formed [M]+ ions by loss of an electron, with [M + 14]+ ions being formed from [M]+ by loss of H2 O and addition of O2 . The fragmentation pathways of the [M]+ cations were further studied by ESI-MS/MS, and several ions produced by gas-phase ion-molecule reactions were detected and characterized, including vanadium-oxo, -peroxo and derivatives. CONCLUSIONS: Several unexpected ions were detected, including [M]+ , [M + 14]+ and ions produced from gas-phase ion-molecule reactions. The study has contributed to the understanding of the structure and character of oxovanadium(IV) complexes, and it could facilitate the design of new oxovanadium catalysts and an understanding of their reaction mechanism.

Analysis of sesterterpenoids from Aspergillus terreus using ESI-QTOF and ESI-IT.

INTRODUCTION: Biosynthesis of terretonin was studied due to the interesting skeleton of this series of sesterterpenoids. Very recently, López-Gresa reported two new sesterterpenoids (terretonins E and F) which are inhibitors of the mammalian mitochondrial respiratory chain. Mass spectrometry (MS), especially tandem mass spectrometry, has been one of the most important physicochemical methods for the identification of trace natural products due to it rapidity, sensitivity and low levels of sample consumption. The potential application prospect and unique skeleton prompted us to study structural characterisation using MS. OBJECTIVE: To obtain sufficient information for rapid structural elucidation of this class of compounds using MS. METHODOLOGY: The elemental composition of the product ions was confirmed by low-energy ESI-CID-QTOF-MS/MS analyses. The fragmentation pathways were postulated on the basis of ESI-QTOF-MS/MS/MS and ESI-IT-MS(n) spectra. Common features and major differences between ESI-QTOF-MS/MS and IT-MS(n) spectra were compared. For ESI-QTOF-MS/MS/MS experiments, capillary exit voltage was raised to induce in-source dissociation. Ammonium acetate or acetic acid were added into solutions to improve the intensity of [M + H]+. The collision energy was optimised to achieve sufficient fragmentation. Some fragmentation pathways were unambiguously proposed by the variety of abundance of fragment ions at different collision energies even without MS(n) spectra. RESULTS: Fragmentation pathways of five representative sesterterpenoids were elucidated using ESI-QTOF-MS/MS/MS and ESI-IT-MS(n) in both positive- and negative-ion mode. The key group of characterising fragmentation profiles was ring B, and these fragmentation patterns are helpful to identify different types of sestertepenoids. CONCLUSION: Complementary information obtained from fragmentation experiments of [M + H]+ (or [M + NH4]+ and [M-H](-) precursor ions is especially valuable for rapid identification of this kind of sesterterpenoid.

Analysis of caffeic acid derivatives from Osmanthus yunnanensis using electrospray ionization quadrupole time-of-flight mass spectrometry.

A series of six caffeic acid derivatives (1-6) in Osmanthus yunnanensis were investigated by electrospray quadrupole time-of-flight tandem mass spectrometry (ESI-QToF-MS/MS) in both negative- and positive-ion modes. High-quality MS/MS spectra of [M + H](+) are generated from high-abundance protonated parent ions obtained by addition of ammonium chloride to the solutions. Fragmentation mechanisms of [M - H](-) and [M + H](+) precursor ions were proposed and elemental compositions of most of the product ions were confirmed on the basis of the high-resolution ESI-collision-induced dissociation (CID)- MS/MS spectra. It was found that the fragment ions at m/z 179, m/z 161, m/z 135 and m/z 134 in negative-ion mode and at m/z 163, m/z 145 and m/z 135 in positive mode should be the characteristic ions of caffeic acid. In addition, the radical fragment ions with high abundance were observed for many caffeic acid derivatives especially for 4. The structural elements of unknown compounds 7 and 8 were tentatively identified on based on tandem mass spectra of known ones.

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.

Cipadesins A-C: novel tetranortriterpenoids from Cipadessa cinerascens.

[structure: see text] Three novel tetranortriterpenoids, cipadesins A-C (1-3), were isolated from the aerial parts of Cipadessa cinerascens. They possess a novel carbon skeleton, in which rings A and C were joined via C-10 and C-11. Their structures were elucidated by spectral evidence. X-ray crystallographic analysis confirmed the structure of 1.

A new triterpene and an antiarrhythmic liriodendrin from Pittosporum brevicalyx.

A new triterpene, 21-O-senecioyl-R(1)-barrigenol (1) and 13 known compounds were isolated from the ethanol extracts of the leaves and bark of Pittosporum brevicalyx (Oliv.) Gagnep. Their structures were elucidated based on spectral data. The antiarrhythmic action of one furofuran lignan, liriodendrin (2), was tested on a model of CaCl(2)-induced arrhythmia and compared with the effect of verapamil. The prophylactic administration of liriodendrin (2) was effective in prolonging latency of arrhythmia and reducing the occurrence of ventricular fibrillation from 75% to 25%. The overall mortality rate was significantly reduced by the prophylactic administration of liriodendrin from 87.5% to 25%. The antiarrhythmic effect of liriodendrin (5.0 mg/kg) was similar to that of verapamil (1.05 mg/kg). Thus, liriodendrin may be a potent suppressor of CaCl(2)-induced arrhythmias.

Analysis of epipolythiodioxopiperazines in fungus Chaetomium cochliodes using HPLC-ESI-MS/MS/MS.

A series of epipolythiodioxopiperazines in the fungus Chaetomium cochliodes was investigated using reversed-phase liquid chromatography with diode array detection and electrospray quadrupole time-of-flight-type tandem mass spectrometry in the positive ion mode. The fragmentation of protonated molecular ions including low-abundance parent ions, [M+H]+ for five known epipolythiodioxopiperazines, dethiotetra(methylthio)chetomin, chaetocochins A-C, and chetomin, was carried out using low-energy collision-induced electrospray ionization tandem spectrometry. It was found that McLafferty rearrangements occurred in the CID processes and produced a complementary pair of characteristic fragment ions containing piperazine rings (fused and unfused), especially to determine the number of S atoms on each ring. The fragmentation differential between [M+H]+ and [M+Na]+ was uncovered. Complementary fragmentation information obtained from [M+H]+ and [M+Na]+ precursor ions is especially valuable for rapid identification of epipolythiodioxopiperazines. A likely known compound, possibly related to chetoseminudin A, and three new species of epipolythiodioxopiperazines from the fungus C. cochliodes were identified or tentatively characterized based on tandem mass spectra of known ones.

Three new limonoids from Cipadessa cinerascens.

Three new limonoids, cipadesins D--F (1--3), together with 8,15-dihydroxy-13E-labdane, beta-sitosterol and beta-daucosterol, were isolated from the leaves and bark of Cipadessa cinerascens. Their structures were elucidated by spectral evidence. X-Ray crystallographic analysis confirmed the structure of 1.

Chiral decalins: preparation from oleanolic acid and application in the synthesis of (-)-9-epi-ambrox.

A novel and versatile process was developed to prepare the trans-decalins Delta9(11)-3beta-acetoxysclareolide (2) and Delta9(11)-3beta-acetoxy-8-epi-sclareolide (3), respectively, with 4a-methoxycarbonyl-2,7,7-trimethyl-1-oxo-cis-decalin-2-ene (4) and its C-3 hydroxyl derivative 5 from oleanolic acid (3beta-hydroxyolean-12-en-28-oic acid, 1). Three key steps were (a) introduction of the AcO-12 group and the C-9,C-11 double bond at ring C of methyl 3beta-acetoxyolean-12-en-28-oate (8) to afford the diene, methyl 3,12-diacetoxyolean-9(11),12-dien-28-oate (11); (b) photolytic cleavage of the C-8,C-14 bond in the diene to give an acetoxy-substituted triene 14; and (c) oxidative cleavage of the triene or its hydrolyzed alpha,beta-unsaturated ketone product with m-CPBA/TsOH to give the cis- and trans-decalins 2-5. Delata9(11)-3beta-Acetoxysclareolide (2) was stereospecifically reduced to give 3beta-acetoxy-9-epi-sclareolide (23), from which (-)-9-epi-ambrox (7) was synthesized.

Four new benzofurans from seeds of Styrax perkinsiae.

Four new benzofurans trans-5-(3-hydroxypropyl)-7-methoxy-2-[2,3-dihydro-3-hydroxymethyl-7-methoxy-2-(3-methoxy-4-hydroxyphenyl)-benzofuran-5-yl]benzofuran (1), (E)-5-(2-formylvinyl)-7-methoxy-2-(3,4-methylenedioxyphenyl)benzofuran (2), 5-(3-butanoyloxypropyl)-7-methoxy-2-(3,4-methylenedioxyphenyl)benzofuran (3), and 5-(3-hydroxypropyl)-7-hydroxy-2-(3,4-methylenedioxyphenyl) benzofuran (4) were isolated from the seeds of Styrax perkinsiae, together with egonol (5), demethoxyegonol (6), egonol acetate (7), demethoxyegonol acetate (8), egonol glucoside (9), egonol gentiobioside (10), egonol gentiotrioside (11), beta-sitosterol (12), and beta-daucosterol (13). Their structures were established by spectroscopic and chemical methods. Compounds 1 and 4 exhibited cytotoxic activity in vitro using two breast cancer cell lines MCF-7 and MDA-MB-231.

Phenolic and triterpene glycosides from the stems of Ilex litseaefolia.

Chemical investigation on the stems of Ilex litseaefolia afforded four new phenolic glycosides, litseaefolosides A-D (1-4), and two new triterpene glycosides, spathodic acid 28-O-beta-d-glucopyranoside (5) and (20S)-niga-ichigoside F1 (6), along with 28 known compounds. The structures of 1-6 were determined on the basis of chemical and spectroscopic evidence. Litseaefoloside C (3) showed inhibitory activities in vitro for alpha-glucosidase and lipase with IC(50) values of 34.0 and 0.31 microg/mL, respectively.

Two diterpenes and three diterpene glucosides from Phlogacanthus curviflorus.

Two new diterpene lactones, phlogacantholides B (1) and C (2), and three new diterpene lactone glucosides, phlogacanthosides A (3), B (4), and C (5), together with lupeol, beta-sitosterol, betulin, beta-daucosterol, (+)-syringaresinol, and (+)-syringaresinol-4-O-beta-D-glucopyranoside, were isolated from the roots of Phlogacanthus curviflorus. Their structures were elucidated by chemical and spectroscopic evidence. The structure, including the relative configuration of phlogacantholide B (1), was confirmed by X-ray crystallographic analysis of its diacetate (6).

Sesterterpenoids, terretonins A-D, and an alkaloid, asterrelenin, from Aspergillus terreus.

Four new sesterterpenoids, terretonins A-D (1-4), and a new alkaloid, asterrelenin (5), together with five known compounds, were isolated from the ethyl acetate extract of a solid-state fermented culture of Aspergillus terreus. Their structures were elucidated on the basis of spectroscopic analysis. The structures of 1, 2, and 5 were confirmed by X-ray crystallographic analysis.

Two pyranocoumarins from the seeds of Calophyllum polyanthum.

Two new pyranocoumarin diastereoisomers, calopolyanolides C (1) and D (2), were isolated from the ethanolic extract of the seeds of Calophyllum polyanthum, along with calopolyanolide A (3), calopolyanolide B (4), calanolide E2 (5), 5,7,3',4'-tetrahydroxyisoflavone (6), 3,4-dihydroxybenzoic acid (7), 3,4,5-trihydroxybenzoic acid (8), 2-hydroxy-4-methoxybenzoic acid (9), beta-sitosterol (10), beta-daucosterol (11), 3,5-dihydroxy-4-methoxybenzoic acid (12), 3,5-dimethoxybenzoic acid (13), and ursolic acid (14). Their structures were determined by MS, UV, and IR data and HMQC, HMBC, and NOESY experiments or by comparing them with authentic samples. X-ray crystallographic analysis confirmed the structure and relative configuration of 1.

Three cyclooctapeptides and one glycoside from Microtoena prainiana.

Three new cyclic octapeptides, microtoenins A-C (1-3), and a new glycoside, 3'''-O-methylcrenatoside (4), along with several known compounds, were isolated from the ethanolic extract of the stems of Microtoena prainiana. Their structures were determined by spectral and chemical evidence. At a concentration of 0.01 mg/mL, 3'''-O-methylcrenatoside (4), crenatoside (5), and isocrenatoside (6) inhibited angiotensin converting enzyme (ACE) activity by more than 30%.