The identification of in vitro metabolites of CKD-732 by liquid chromatography/tandem mass spectrometry

The structural elucidation of fourteen metabolites of CKD-732, formed in vitro with rat liver microsomes, was performed using high-performance liquid chromatography/electrospray ionization-tandem mass spectrometry (HPLC/ESI-MS/MS). To identify proposed structures of the metabolites, the product ion mass spectra of the protonated molecules ([M + H]+), the retention times on reversed-phase HPLC, and UV-Vis spectra were utilized. Characteristic product ions for the identification of CKD-732 metabolites were observed at m/z 231, 236, and 252. The fragment ions at m/z 236 and 252 indicated the unchanged form and the N-oxide of the dimethylaminoethoxycinnamoyl group, respectively. The ion at m/z 231 indicated the presence of the hydroxylated form of the fumagillol group. The N-oxide of CKD-732, which was detected at m/z 515 and eluted later than CKD-732 in the reversed-phase HPLC system, was measured as a major metabolite. Three cis-trans isomers were also found.     

Investigation of the electrochemical oxidation products of zotepine and their fragmentation using on-line electrochemistry/electrospray ionization mass spectrometry

When zotepine, an antipsychotic drug, was electrochemically oxidized using electrospray ionization mass spectrometry (ESI-MS) coupled with a microflow electrolytic cell, [M + 16 + H]+ (m/z 348), [M-H]+ (m/z 330) and [M-14 + H]+ (m/z 318) were observed as electrochemical oxidation product ions (M represents the zotepine molecule). Although a major fragment ion that was derived from the dimethyl aminoethyl moiety was observed only at m/z 72 in the collision-induced dissociation (CID) spectrum of zotepine, new fragments such as m/z 315 and 286 ions could be generated in the CID spectrum by combining electrochemical oxidation and CID. Since these fragments were relatively specific with high ion strength, it was thought that they would be useful for developing a sensitive LC-MS/MS assay. The S-oxide and N-demethylated products were detected by electrolysis assuring that a portion of P450 metabolites of zotepine could be mimicked by the electrochemistry/electrospray ionization mass spectrometry (EC/ESI-MS) system.     

Key fragments for identification of positional isomer pair in glucuronides from the hydroxylated metabolites of RT-3003 (Vintoperol) by liquid chromatography/electrospray ionization mass spectrometry.

The mass spectral properties of glucuronides of the 9- and 10-hydroxylated metabolites of RT-3003 (Vintoperol; (-)-1beta-ethyl-1alpha-hydroxymethyl-1,2,3,4,6,7, 12balpha-octahydroindolo[2,3-a]quinolizine), which were fractionated by high-performance liquid chromatography with fluorescence detection, were investigated using the positive ion electrospray ionization mode. These glucuronides showed predominantly the protonated molecular ion ([M + H](+) ion), and the [M + H](+) ion provided a characteristic product ion spectrum in which abundant ions were obtained at m/z 301, 160 and 142. The first ion, corresponding to the [aglycone + H](+) ion, was produced by neutral loss of the glucuronic acid moiety from the [M + H](+) ion. The product ion spectrum of the [M + H](+) ion of hydroxy-RT-3003 revealed a number of ions common to the glucuronide spectra, suggesting that other two ions observed most likely represent fragmentation of hydroxy-RT-3003. In turn, these glucuronides were positional isomers with respect to the binding site of glucuronic acid. The structures of the isomer pairs were discriminated by the presence of the ion of m/z 318 or 336 in the product ion spectrum. These ions were produced by fission of the C-ring, the same as for the formation of the ions of m/z 160 and 142, as were observed in the product ion spectrum from the [M + H](+) ion of hydroxy-RT-3003. For the formation of these ions, an unusual fragmentation process was proposed, and these ion structures were supported by evidence from the accurate mass measurement data. Additionally, in the sulfates of hydroxylated metabolites, a similar product ion corresponding to the ion of m/z 336 found in the phenolic glucuronides was observed, and was applied for identification of the sulfate metabolites.     

电喷雾质谱法分析假单胞菌的代谢产物鼠李糖脂

采用电喷雾质谱(ESI-MS)结合碰撞诱导解离(CA)技术,分析了假单胞菌BS-03,利用甘油产的鼠李糖脂提取物。根据一级和二级质谱图确定了提取物中存在23种鼠李糖脂组分,主要由4种物质(RhC10、RhC10C10、Rh2C10和Rh2C10C10)构成,其中前3种的丰度较高也较平均。该提取物中单鼠李糖脂的含量高于双鼠李糖脂,并且双鼠李糖脂的二级质谱图中普遍存在强度较高的m/z为205、247的特征碎片离子,而单鼠李糖脂中却不存在此特征碎片离子。     

Mass spectrometric study of persistent acid metabolites of nonylphenol ethoxylate surfactants

A mass spectrometric study was carried out on two nonylphenoxycarboxylic acids, NP1EC and NP2EC (where 1 and 2 indicate the number of ethoxylate units attached to the nonylphenoxy moiety), that are persistent metabolites of widely used nonionic surfactant nonylphenol ethoxylates. In a gas chromatographic/mass spectrometric (GC/MS) study of the methyl esters of NP1EC and NP2EC, two series of fragment ions were observed in electron ionization (EI) mass spectra; m/z (179 + 14n, n = 0-7) and m/z (105 + 14n, n = 0-4) for NP1ECMe and m/z (223 + 14n, n = 0-7) and m/z (107 + 14n, n = 0-5) for NP2ECMe. Similarity indices were used to compare quantitatively the mass spectra of isomers. The mass spectra of two isomers were found to be similar whereas those of the remaining isomers were readily distinguishable from each other. The abundant fragment ions of the two NPECMes were investigated further by GC/MS/MS; product ions resulting from cleavage in the alkyl moiety, cleavage in the ECMe moiety and cleavage in both moieties were detected. Possible structures of the nonyl groups in the two esters were inferred. GC/chemical ionization (CI) mass spectra of the NPECMes with isobutane as reagent gas showed characteristic hydride ion-abstracted fragment ions shifted by 1 Da from those in the corresponding EI mass spectra. The sensitivity of a selected ion monitoring quantitation method for the NPECMes is enhanced under CI conditions compared with that under EI conditions. With electrospray ionization MS/MS, [M - H](-) ions of NP1EC (m/z 277) and NP2EC (m/z 321) were observed and, upon collision-induced dissociation of [M - H](-) of each of the two acids, fragment ions of m/z 219 corresponding to deprotonated nonylphenol, were observed in each case. Based on this observation, a rapid, simple and reliable selected product ion quantitation method is proposed for NP1EC and NP2EC.     

Mass spectrometric characterization of toremifene metabolites in human urine by liquid chromatography-tandem mass spectrometry with different scan modes

The metabolism and excretion of toremifene were investigated in one healthy male volunteer after a single oral administration of 120 mg toremifene citrate. Different liquid chromatographic/tandem mass spectrometric (LC/MS/MS) scanning techniques were carried out for the characterization of the metabolites in human urine for doping control purposes. The potential characteristic fragmentation pathways of toremifene and its major metabolites were presented. An approach for the metabolism study of toremifene and its analogs by liquid chromatography-tandem mass spectrometry was established. Five different LC/MS/MS scanning methods based on precursor ion scan (precursor ion scan of m/z 72.2, 58.2, 44.2, 45.2, 88.2 relative to five metabolic pathways) in positive ion mode were assessed to recognize the metabolites. Based on product ion scan and precursor ion scan techniques, the metabolites were proposed to be identified as 4-hydroxy-toremifene (m/z 422.4), 4'-hydroxy-toremifene (m/z 422.4), α-hydroxy-toremifene (m/z 422.4), 3,4-dihydroxy-toremifene (m/z 404.2), toremifene acid (m/z 402.2), 3-hydroxy-4-methoxy-toremifene (m/z 456.2), dihydroxy-dehydro-toremifene (m/z 440.2), 3,4-dihydroxy-toremifene (m/z 438.2), N-demethyl-4-hydroxy-toremifene (m/z 408.3), N-demethyl-3-hydroxy-4-methoxy-toremifene (m/z 438.3). In addition, a new metabolite with a protonated molecule at m/z 390.3 was detected in all urine samples. The compound was identified by LC/MS/MS as N-demethyl-4,4'-dihydroxy-tamoxifene. The results indicated that 3,4-dihydroxy-toremifene (m/z 404.2), toremifene acid (m/z 402.2) and N-demethyl-4,4'-dihydroxy-tamoxifene (m/z 390.3) were major metabolites in human urine.     

山奈酚的电喷雾质谱裂解途径

采用电喷雾质谱技术对山奈酚的质谱过程进行了表征,并用量子化学方法对山奈酚的质谱裂解途径进行了理论研究。 依据密度泛函理论,在B3LYP/6-31G(d)水平,对山奈酚的各质谱碎片离子进行了几何结构优化,确定了各碎片的稳定结构;然后,在ROB3LYP/ 6-311++G(2d,2p)水平计算了形成各碎片离子所需的键断裂能,进而推导出了山奈酚的质谱碎裂途径。 计算结果显示,山奈酚主要通过C环碎裂而发生裂解,出现碎片m/z 284.7、256.7、228.7、210.7、184.8、168.7和150.7,其中m/z 210.7的碎片离子键断裂能最小,m/z 150.7的碎片离子键断裂能最大,说明前者很容易由母离子碎片形成,后者较难由母离子碎片形成。     

Characterization of metabolites of a novel histamine H(2)-receptor antagonist, lafutidine, in human liver microsomes by liquid chromatography coupled with ion trap mass spectrometry

The metabolism of lafutidine in human liver microsomes was studied using liquid chromatography/ion trap mass spectrometry with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) sources. A total of 14 metabolites were identified including hydroxylated lafutidine and sulfonyl lafutidine as the major metabolites. The chemical properties and the MS(n) behaviors of lafutidine and all of its identified metabolites were studied in detail. Lafutidine had a fragmentation pattern as a result of homolytic bond cleavage in the MS/MS spectrum. This cleavage can form an odd-electron ion with the loss of furan-2-ylmethyl radical (-81 Da with a proton shift), which then sequentially loses neutral groups in the MS(3) spectrum. This fragmentation sequence was also observed from the metabolites with the unchanged sulfinyl moiety. When the sulfinyl moiety was oxidized to the sulfonyl moiety, this fragmentation sequence did not exist, which could be used to identify S-oxidation metabolites of lafutidine. In general, N-oxides could produce distinct [M+H-O](+) ions under LC/APCI-MS due to the thermal activation in the desolvation region of the API source, which could be used to identify N-oxidation metabolites of lafutidine. In order to avoid the possibility of false positives, the MS/MS spectrum of the [M+H-O](+) ion was compared with that of the non-N-oxidation metabolites or parent drug in the APCI source. If they were consistent, the structure could be finally confirmed. The exact masses for lafutidine and lafutidine N-oxide fragment ions were determined using an LTQ/Orbitrap mass spectrometer.     

Gas-phase reactions for selective detection of the explosives TNT and RDX

Highly selective gas-phase reactions with ethyl vinyl ether (EVE) of major electron (EI) and chemical ionization (CI) fragment ions of the explosives TNT and RDX have been uncovered. The fragment ion of m/z 210 from TNT undergoes [4(+)+ 2] cycloaddition with EVE to form an oxo-iminium ion of m/z 282, which dissociates by acetaldehyde loss after a [1,5-H] shift to form a quinolynium ion of m/z 238. The fragment ion of m/z 149 from RDX reacts with EVE by a formal vinylation reaction, that is, the elusive cyclic adduct loses ethanol to yield a nitro-iminium ion of m/z 175, which reacts further with EVE to form a second cyclic product ion of m/z 247. Calculations and MS/MS experiments support the proposed structures. These highly characteristic reactions of diagnostic EI and CI fragment ions improve selectivity for TNT and RDX detection.     

Qualitative determination of urinary morphine by capillary zone electrophoresis and ion trap mass spectrometry

A rapid, sensitive method for the determination of morphine and amphetamine was developed using capillary zone electrophoresis coupled with electrospray interface (ESI), ion-trap tandem mass spectrometry (CE-ESI-MS2). Morphine and amphetamine were separated in 20 mM ammonium acetate buffer (pH 6.6) and detected by ion-trap mass detector in different analytical time segments (0-6.25 min for amphetamine and 6.25-12.0 min for morphine) in which the tune file for each compound was used separately. Molecular ions of morphine (m/z 286) and amphetamine (m/z 136) were detected at 5.77 and 6.83 min, respectively, while product ions of MS2 for each compound (m/z 229, 201 for morphine and m/z 119 for amphetamine) were detected almost exactly at the same time with their parent compounds. The limits of detection (LOD) for MS2 determination were 30 and 50 ng/mL for amphetamine and morphine, respectively, with an S/N ratio of 3. For more sensitive detection of morphine, the sample was injected for a longer time (i.e., 80 s) and hydrodynamically transported into a CE capillary for MS detection. Morphine and its product ion appear at 0.36 and 0.39 min on the ion chromatogram, respectively, with a five-fold increase of detection sensitivity (LOD, 10 ng/mL). The CE-MS system thus established was further applied for forensic urine samples screened as morphine-positive by fluorescence polarization immunoassay (FPIA). These results indicated the feasibility of CE-ESI-MS2 for confirmative testing of morphine in urine sample.     

Determination of the metabolites of gestrinone in human urine by high performance liquid chromatography, liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry

Gestrinone was studied by high performance liquid chromatography (HPLC) for screening and by gas chromatography/mass spectrometry (GC/MS) for confirmation. When the chromatograms of blank, spiked urine and dosed urine were compared by HPLC, two unknown metabolites were found and these were excreted as the conjugated forms. Metabolites 1 and 2 were tested by LC/MS and LC/MS/MS and both had parent ions at m/z 325. The fragment ion of metabolite 1 was at m/z 263 and ions for metabolite 2 were m/z 307 [MH - H(2)O](+), 289, 279 and 241. LC/MS/MS of m/z 263 as the parent ion of metabolite 1 gave fragment ions at m/z 245 and 217, which were assumed to be [263 - H(2)O](+) and [235 - H(2)O](+), respectively. The trimethylsilyl (TMS)-enol-TMS ether derivative of gestrinone displayed three peaks in its GC/MS chromatogram, formed by tautomerism.     

Identification of diphenhydramine metabolites in human urine by capillary electrophoresis-ion trap-mass spectrometry

The identification of diphenhydramine (DH) metabolites that are frequently observed in the capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) analyses of alkaline liquid/liquid and solid-phase extracts of patient urines is demonstrated. Having standards for DH and diphenhydramine-N-oxide (DHNO), the presence of these two compounds could be confirmed in urines that were collected overnight after administration of 25 mg DH chloride. Using CZE coupled to ion-trap mass spectrometry (CE-MS(n)) with positive electrospray ionization and an acetate buffer at pH 5.6, the [M+H](+) ions of DH (m/z = 256), DHNO (m/z = 272), and nordiphenhydramine (NDH, m/z = 242) and their fragmentation to a common m/z 167 product ion (diphenylcarbinol moiety) was monitored. The data indicate that all three compounds are cations in an acidic environment, the migration order being NDH, DH, and DHNO. Data obtained under negative electrospray ionization conditions suggest the presence of diphenylmethoxyacetic acid-glycine amide ([M-H](-) ion of m/z 298 and fragmentation to m/z 254, loss of CO(2)), a metabolite that could tentatively be assigned to a characteristic peak observed in the MEKC electropherogram at alkaline pH. The data presented in this paper illustrate the value of using CE-MS(n) for identification of urinary drug metabolites for which no standards are available.     

In vitro and in vivo metabolism of pyronaridine characterized by low-energy collision-induced dissociation mass spectrometry with electrospray ionization

The in vitro and in vivo metabolism of pyronaridine, an antimalarial agent, was investigated in rats and humans. In vitro incubation of pyronaridine with rat and human liver microsomes resulted in the formation of 11 metabolites, with pyronaridine quinoneimine (M3) as the major metabolite. The structures of pyronaridine metabolites were characterized on the basis of the product ion mass spectra obtained under low-energy collision-induced dissociation (CID) ion trap mass spectrometry. Both pyronaridine (m/z 518) and M3 (m/z 516) produced the same product ion (m/z 447). These results could be explained by the characteristic neutral loss of a 69 Da fragment from M3 via gamma-H rearrangement and 1,7 sigmatropic shift, whereas the neutral loss of a 71 Da fragment from the pyronaridine occurred by charge site-initiated heterolytic cleavage. These fragmentations were further supported by the tandem mass spectrum of D(3)-pyronaridine. Other metabolites generated in the microsomal incubations were carbonylated, hydroxylated and O-demethylated derivatives. Pyronaridine and its metabolites were detected in both feces and urine after intraperitoneal administration to rats. The in vivo metabolic profile in rats was different from the in vitro profile. M3, a chemically reactive quinonimine, was not detected whereas O-demethylated derivatives (M14, M15, M16, and M19) were identified in fecal and urinary extracts. The role of quinoneimine metabolites in pyronaridine-caused toxicity should be further evaluated, although these metabolites or their conjugates were not detected in urine and feces.     

Characteristic fragmentation patterns of the trimethylsilyl and trimethylsilyl-oxime derivatives of various saccharides as obtained by gas chromatography coupled to ion-trap mass spectrometry

The fragmentation patterns of selected glycosidic linkage containing non-reducing (methylmannoside, methylgalactoside, lactitol, sucrose, trehalose, raffinose, erlose, melezitose) and reducing saccharides (maltose, cellobiose, lactose, melibiose, palatinose, primeverose, rutinose) have been compared as their trimethylsilyl and as their trimethylsilyl-oxime derivatives. Fragmentation characteristics of the glycosidic linkage containing trimethylsilyl-oxime derivatives have been investigated at the first time: these spectra are not available in the official libraries (NIST, Wiley). Applying gas chromatography-ion trap mass spectrometry, informative fragments of high masses with high intensities have been obtained. Results confirmed characteristic differences between the simple trimethylsilyl derivative providing non-reducing glycosides and the trimethylsilyl, syn and antioxime species. Fragmentation starts at the glycosidic linkage resulting in the case of the non-reducing di- and trisaccharides in two, identical fragments of ring structure, with the abundant selective fragment ion at m/z=361. In the case of reducing disaccharides fragmentation provides two different moieties: one moiety of ring structure at m/z=361, and one of the open chain trimethylsilyl-oxime moiety with two special fragment ions at m/z=361 and at m/z=538. These fragmentation patterns proved to be independent on the position of the glycosidic linkage. Distribution of the selective fragment ions, obtained from their total ion current elutions, was evaluated on a quantitative basis, expressed in percentages of the total of ions formed. Reproducibility in the formation of these selective fragment ions, depending on their amount to be fragmented, proved to be proper for identification and quantitation purposes, equally. On this basis, in addition to the authentic ones, also two reducing disaccharides (primeverose and rutinose), as authentic compounds not available on the market, were identified and quantified in natural matrices.     

Determination of patulin in apple juice by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

An HPLC-MS-MS method with selected reaction monitoring (SRM) for the determination of patulin in apple juice samples is described. Mass spectrometric detection was accomplished following atmospheric pressure chemical ionization (APCI) in both positive and negative ion modes. Collision induced dissociation (CID) of the protonated molecular ion led initially to the loss of H2O (fragment m/z 137). At higher energies CO is lost from both the protonated parent molecule (fragment m/z 127) and the dehydrated molecular ion (fragment m/z 109). In contrast, CID of the deprotonated molecular ion led initially to the fragment at m/z 109 corresponding to the loss of either CO2 or acetaldehyde, followed at higher CID energy by the loss of H2O (fragment m/z 135) and CO (fragment m/z 125) from the deprotonated molecular ion. Detection in the negative ion mode proved superior and a linear response was observed over the injected range from 6 to 200 ng patulin. Apple juice samples spiked with patulin between 10 and 135 microg/l were analyzed following liquid-liquid extraction with ethyl acetate and clean up with sodium carbonate. Utilizing reversed-phase HPLC with acetonitrile-water (10:90) at 0.5 ml/min, levels down to 10 microg/l were readily quantified and a detection limit of 4 microg/l was attainable at a signal-to-noise (SIN) ratio of 4. The MS data for the spiked samples compared well to the UV data and when plotted against each other displayed a correlation coefficient (R) of 0.99.     

Tamoxifen metabolism in rat liver microsomes: identification of a dimeric metabolite derived from free radical intermediates by liquid chromatography/mass spectrometry

Tamoxifen has been shown to be a potent liver carcinogen in rats, and generates covalent DNA adducts. On-line high performance liquid chromatography/electrospray ionisation mass spectrometry (HPLC/ESI-MS) has been used to further study the metabolites of tamoxifen formed by rat liver microsomes in the presence of NADPH with a view to identifying potential reactive metabolites which may be responsible for the formation of DNA adducts, and liver carcinogenesis. A metabolite has been detected with a protonated molecule at m/z 773. The mass of this compound is consistent with a dimer of hydroxylated tamoxifen (m/z 388). Analysis of 4-hydroxytamoxifen incubated with a rat liver microsomal preparation showed the formation of a similar metabolite with an apparent MH+ ion at m/z 773, believed to be a dimer of 4-hydroxytamoxifen formed by a free radical reaction. The retention time for this metabolite from 4-hydroxytamoxifen is identical to that of the tamoxifen metabolite, suggesting that these two compounds are the same. The levels of the dimer were higher when 4-hydroxytamoxifen was used as substrate and, in addition, two isomers were detected. It is proposed that tamoxifen was first converted to arene oxides which react with DNA or to 4-hydroxytamoxifen, either directly or via 3,4-epoxytamoxifen, which then undergoes activation via a free radical reaction to give reactive intermediates which can then react with DNA and protein, or with themselves, to give the dimers (m/z 773).     

Detection and characterization by mass spectrometry of radical adducts produced by linoleic acid oxidation

The formation of linoleic acid radical species under the oxidative conditions of the Fenton reaction (using hydrogen peroxide and Fe (II)) was monitored by FAB-MS and ES-MS using the spin trap 5,5-dimethyl-1-pyrrolidine-N-oxide, DMPO. Both the FAB and ES mass spectra were very similar and showed the presence of ions corresponding to carbon- and oxygen centered spin adducts (DMPO/L*, DMPO/LO*, and DMPO/LOO*). Cyclic structures, formed between the DMPO oxygen and the neighboring carbon of the fatty acid, were also observed. Electrospray tandem mass spectrometry of these ions was performed to confirm the proposed structure of these adducts. All MS/MS spectra showed an ion at m/z 114, correspondent to the [DMPO + H]+, and a fragment ion due to loss of DMPO (loss of 113 Da), confirming that they are DMPO adducts. ES-MS/MS spectra of alkoxyl radical adducts (DMPO/LO*) showed an additional ion at m/z 130 [DMPO - O + H]+, while ES MS/MS of peroxyl radical adducts (DMPO/LOO*) showed a fragment ion at m/z 146 [DMPO - OO + H]+, confirming both structures. Other fragment ions were observed, such as alkyl acylium radical ions, formed by cleavage of the alkyl chain after loss of water and the DMPO molecule. The identification of fragment ions observed in the MS/MS spectra of the different DMPO adducts suggests the occurrence of structural isomers containing the DMPO moiety both at C9 and C13. The use of ES tandem mass spectrometry, associated with spin trapping experiments, has been shown to be a valuable tool for the structural characterization of carbon and oxygen-centered spin adducts of lipid radicals.     

Thermochemistry of N-N containing ions: a threshold photoelectron photoion coincidence spectroscopy study of ionized methyl- and tetramethylhydrazine

The unimolecular dissociation reactions of the methylhydrazine (MH) and tetramethylhydrazine (TMH) radical cations have been investigated using tandem mass spectrometry and threshold photoelectron photoion coincidence spectroscopy in the photon energy ranges 9.60-31.95 eV (for the MH ion) and 7.74-29.94 eV (for the TMH ion). Methylhydrazine ions (CH3NHNH2(+*)) have three low-energy dissociation channels: hydrogen atom loss to form CH2NHNH2(+) (m/z 45), loss of a methyl radical to form NHNH2(+) (m/z 31), and loss of methane to form the fragment ion m/z 30, N2H2(+*). Tetramethylhydrazine ions only exhibit two dissociation reactions near threshold: that of methyl radical loss to form (CH3)2NNCH3(+) (m/z 73) and of methane loss to form the fragment ion m/z 72 with the empirical formula C3H8N2(+*). The experimental breakdown curves were modeled with Rice-Ramsperger-Kassel-Marcus theory, and it was found that, particularly for methyl radical loss, variational transition state theory was needed to obtain satisfactory fits to the data. The 0 K enthalpies of formation (delta(f)H0) for all fragment ions (m/z 73, m/z 72, m/z 45, m/z 31, and m/z 30) have been determined from the 0 K activation energies (E0) obtained from the fitting procedure: delta(f)H0[(CH3)2NNCH3(+)] = 833 +/- 5 kJ mol(-1), delta(f)H0 [C3H8N2(+*)] = 1064 +/- 5 kJ mol(-1), delta(f)H0[CH2NHNH2(+)] = 862 +/- 5 kJ mol(-1), delta(f)H0[NHNH2(+)] = 959 +/- 5 kJ mol(-1), and delta(f)H0[N2H2(+*)] = 1155 +/- 5 kJ mol(-1). The breakdown curves have been measured from threshold up to h nu approximately 32 eV for both hydrazine ions. As the photon energy increases, other dissociation products are observed and their appearance energies are reported.     

Discovery of new analogs of the marine biotoxin azaspiracid in blue mussels (Mytilus edulis) by ultra-performance liquid chromatography/tandem mass spectrometry

Azaspiracids (AZAs) are a group of lipophilic marine biotoxins that were first discovered in blue mussels harvested in 1995 in Killary Harbour on the west coast of Ireland. At least eight people fell ill after the consumption of contaminated mussels and developed symptoms of nausea, stomach cramps, vomiting and severe diarrhoea. Until now, eleven different analogs of these toxins have been described, with a twelfth one theoretically postulated. This paper describes the detection and identification of twenty new analogs of azaspiracid, including dihydroxy-AZAs and carboxy-AZAs, using state-of-the-art techniques including ultra-performance liquid chromatography (UPLC) and tandem mass spectrometry (MS/MS). Blue mussels (Mytilus edulis) from a toxic event of the northwest coast of Ireland in 2005 were extracted and analysed using LC/MS. The mass spectra obtained from different instruments enabled identification of previously unknown analogs of azaspiracid with additional hydroxyl and carboxyl substituents. Mass fragmentation patterns of the dihydroxy-AZAs indicated the positions of these substituents to be at the C3 and C23 position. The previously theoretically postulated AZA12 was also observed in this study. Product ion spectra showed the presence of a unique fragment ion at m/z 408 for all C23-hydroxylated analogs. This fragmentation competes with the fragmentation leading to m/z 362, a fragment ion that has shown to be present in all AZAs. The novel analogs have not been seen in plankton or water samples and are believed to be metabolites of AZAs formed in mussels. All the new AZA analogs were present at low concentrations in the shellfish and it is probably safe to assume that they do not pose a risk for the shellfish consumer.     

13-乙酰基-9-甲基-11-羰基-8-氧代-10,12-二氮杂三环[7.3.1.02,7]十三碳-2,4,6-三烯的一锅煮合成和结构表征

An efficient and environmentally friendly procedure for the one-pot synthesis of 13-acetyl-9-methyl-11-oxo-8-oxa-10,12-diazatricyclo7.3.1.02,7trideca-2,4,6-triene from salicylaldehyde, acetylacetone and urea via Biginelli condensation and intramolecular Michael-addition by using magnesium bromide as an inexpensive and easily available catalyst in a solvent-free condition is described. The structural elucidation of the product is reported by 1H- and 13C-NMR spectra. The product can also be identified by its EI TOF mass spectrometry based on the molecular ion at m/s 246(10%) and on the fragment ions in which two nitrogen atoms are remained. Three kinds of characteristic fragmentation pathways from the molecular ion were observed. One is the loss of the OH radical to form the dihydropyrimidinone cation at m/z 229(48%), followed by elimination of a molecular methane forming the pyrimidinone cation at m/z 213(27%). The second is the cleavage of the C6H4OH radical, and the formation of the dihydropyrimidinone cation at m/z 153(24%). The third one is the loss of MeC=O radical to afford the oxygen-bridged fragment ion at m/z 203(33%).