Analysis of dammar resin with MALDI‐FT‐ICR‐MS and APCI‐FT‐ICR‐MS

Comprehensive analysis of high‐resolution mass spectra of aged natural dammar resin obtained with Fourier transform ion cyclotron resonance mass spectrometer (FT‐ICR‐MS) using matrix‐assisted laser desorption/ionization (MALDI) and atmospheric pressure chemical ionization (APCI) is presented. Dammar resin is one of the most important components of painting varnishes. Dammar resin is a terpenoid resin (dominated by triterpenoids) with intrinsically very complex composition. This complexity further increases with aging. Ten different solvents and two‐component solvent mixtures were tested for sample preparation. The most suitable solvent mixtures for the MALDI‐FT‐ICR‐MS analysis were dichloromethane‐acetone and dichloromethane‐ethanol. The obtained MALDI‐FTMS mass spectrum contains nine clusters of peaks in the m/z range of 420–2200, and the obtained APCI‐FTMS mass spectrum contains three clusters of peaks in the m/z range of 380–910. The peaks in the clusters correspond to the oxygenated derivatives of terpenoids differing by the number of C₁₅H₂₄ units. The clusters, in turn, are composed of subclusters differing by the number of oxygen atoms in the molecules. Thorough analysis and identification of the components (or groups of components) by their accurate m/z ratios was carried out, and molecular formulas (elemental compositions) of all major peaks in the MALDI‐FTMS and APCI‐FTMS spectra were identified (and groups of possible isomeric compounds were proposed). In the MALDI‐FTMS and APCI‐FTMS mass spectrum, besides the oxidized C₃₀, triterpenoids also peaks corresponding to C₂₉ and C₃₁ derivatives of triterpenoids (demethylated and methylated, correspondingly) were detected. MALDI and APCI are complementary ionization sources for the analysis of natural dammar resin. In the MALDI source, preferably polar (extensively oxidized) components of the resin are ionized (mostly as Na⁺ adducts), whereas in the APCI source, preferably nonpolar (hydrocarbon and slightly oxidized) compounds are ionized (by protonation). Either of the two ionization methods, when used alone, gives an incomplete picture of the dammar resin composition. Copyright © 2012 John Wiley & Sons, Ltd.     

Simple and fast determination of phenolic compounds from different varieties of olive oil by nonaqueous capillary electrophoresis with UV‐visible and fluorescence detection

In this article, we proposed very simple procedures to analyze important phenolic compounds in olive oil samples from different olive varieties. A nonaqueous CE method has been employed. The main phenolic alcohols in virgin olive oil (tyrosol and hydroxytyrosol) and some among the most abundant secoiridoid aglycone derivatives (dialdehydic form of decarboxymethyl elenoic acid linked to hydroxytyrosol, an isomer of oleuropein aglycone and the dialdehydic form of decarboxymethyl elenoic acid linked to tyrosol) were determined by a direct injection into the capillary of the olive oil dissolved in 1‐propanol 1:1 v/v. For the determination of compounds present at lower concentrations, a very simple liquid–liquid extraction method with ethanol has been proposed. The extraction was performed using a relationship 5:1 w/v olive oil/ethanol to achieve the necessary preconcentration of the analytes and the ethanolic extracts were directly injected into the capillary to obtain a very important time reduction. Good recoveries were obtained with both the procedures, using an internal standard. Finally, these procedures were applied to the analysis of these compounds in extra virgin olive oil samples from different varieties of olive.     

Characterization of isomers of oleuropein aglycon in olive oils by rapid‐resolution liquid chromatography coupled to electrospray time‐of‐flight and ion trap tandem mass spectrometry

In this work, rapid‐resolution liquid chromatography (RRLC) coupled to electrospray ionization time‐of‐flight mass spectrometry (ESI‐TOF‐MS) and ion trap multiple mass spectrometry (IT‐MSⁿ) has been applied to separate and characterize eleven isomers of oleuropein aglycon in fourteen Spanish extra‐virgin olive oils. After the extra‐virgin olive oil sample had been dissolved in hexane and cleaned up by a diol‐bonded phase solid‐phase extraction (SPE) cartridge, the eluting extract was resolved in methanol and analyzed on an Angilent 1200 system with a 4.6 × 150 mm, 1.8 µm Zorbax Eclipse plus C18 column. Mass spectrometry was carried out on a Bruker Daltonics microTOF mass spectrometer and a Bruker Daltonics ion trap mass spectrometer. The characterization of isomers of oleuropein aglycon was based on accurate mass data and the isotope function of characteristic fragment ions in the studied compounds by TOF‐MS, and the fragment ions were further confirmed by IT‐MSⁿ. The fragmentation pathway of oleuropein aglycon was successfully elucidated and all possible transformations among isomers of oleuropein aglycon were suggested. Copyright © 2008 John Wiley & Sons, Ltd.     

A 2‐D‐HPLC‐CE platform coupled to ESI‐TOF‐MS to characterize the phenolic fraction in olive oil

A 2‐D‐HPLC/CE method was developed to separate and characterize more in depth the phenolic fraction of olive oil samples. The method involves the use of semi‐preparative HPLC (C18 column 250×10 mm, 5 μm) as a first dimension of separation to isolate phenolic fractions from commercial extra‐virgin olive oils and CE coupled to TOF‐MS (CE‐TOF‐MS) as a second dimension, to analyze the composition of the isolated fractions. Using this method, a large number of compounds were tentatively identified, some of them by first time, based on the information concerning high mass accuracy and the isotopic pattern provided by TOF‐MS analyzer together with the chemical knowledge and the behavior of the compounds in HPLC and CE. From these results it can be concluded that 2‐D‐HPLC‐CE‐MS provides enough resolving power to separate hundreds of compounds from highly complex samples, such as olive oil. Furthermore, in this paper, the isolated phenolic fractions have been used for two specific applications: quantification of some components of extra‐virgin olive oil samples in terms of pure fractions, and in vitro studies of its anti‐carcinogenic capacity.     

Characterization of superoxide dismutase 1 (SOD‐1) by electrospray ionization‐ion mobility mass spectrometry

In this paper, we report nano‐electrospray ionization‐ion mobility mass spectrometry (nano‐ESI‐IM‐MS) characterization of bovine superoxide dismutase (SOD‐1) and human SOD‐1 purified from erythrocytes. SOD‐1 aggregates are characteristic of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease in humans that could be triggered by dissociation of the native dimeric enzyme (Cu₂,Zn₂‐dimer SOD‐1). In contrast to ESI‐MS, nano‐ESI‐IM‐MS allowed an extra dimension for ion separation, yielding three‐way mass spectra (drift time, mass‐to‐charge ratio and intensity). Drift time provided valuable structural information related to ion size, which proved useful to differentiate between the dimeric and monomeric forms of SOD‐1 under non denaturing conditions. In order to obtain detailed structural information, including the most relevant post‐translational modifications, we evaluated several parameters of the IM method, such as sample composition (10 mM ammonium acetate, pH 7) and activation voltages (trap collision energy and cone voltage). Neutral pH and a careful selection of the most appropriate activation voltages were necessary to minimize dimer dissociation, although human enzyme resulted less prone to dissociation. Under optimum conditions, a comparison between monomer‐to‐dimer abundance ratios of two small sets of blood samples from healthy control and ALS patients demonstrated the presence of a higher relative abundance of Cu,Zn‐monomer SOD‐1 in patient samples. Copyright © 2013 John Wiley & Sons, Ltd.     

ESI‐MS/MS analysis of protonated N‐methyl amino acids and their immonium ions

Methylation is one of the important posttranslational modifications of biological systems. At the metabolite level, the methylation process is expected to convert bioactive compounds such as amino acids, fatty acids, lipids, sugars, and other organic acids into their methylated forms. A few of the methylated amino acids are identified and have been proved as potential biomarkers for several metabolic disorders by using mass spectrometry–based metabolomics workstation. As it is possible to encounter all the N‐methyl forms of the proteinogenic amino acids in plant/biological systems, it is essential to have analytical data of all N‐methyl amino acids for their detection and identification. In earlier studies, we have reported the ESI‐MS/MS data of all methylated proteinogenic amino acids, except that of mono‐N‐methyl amino acids. In this study, the N‐methyl amino acids of all the amino acids ( 1 ‐ 21 ; including one isomeric pair) were synthesized and characterized by ESI‐MS/MS, LC/MS/MS, and HRMS. These data could be useful for detection and identification of N‐methyl amino acids in biological systems for future metabolomics studies. The MS/MS spectra of [M + H]⁺ ions of most N‐methyl amino acids showed respective immonium ions by the loss of (H₂O, CO). The other most common product ions detected were [MH‐(NH₂CH₃]⁺, [MH‐(RH)]⁺ (where R = side chain group) ions, and the selective structure indicative product ions due to side chain and N‐methyl group. The isomeric/isobaric N‐methyl amino acids could easily be differentiated by their distinct MS/MS spectra. Further, the MS/MS of immonium ions inferred side chain structure and methyl group on α‐nitrogen of the N‐methyl amino acids.     

Extra virgin (EV) and ordinary (ON) olive oils: distinction and detection of adulteration (EV with ON) as determined by direct infusion electrospray ionization mass spectrometry and chemometric approaches

Extra virgin (EV), the finest and most expensive among all the olive oil grades, is often adulterated by the cheapest and lowest quality ordinary (ON) olive oil. A new methodology is described herein that provides a simple, rapid, and accurate way not only to detect such type of adulteration, but also to distinguish between these olive oil grades (EV and ON). This approach is based on the application of direct infusion electrospray ionization mass spectrometry in the positive ion mode, ESI(+)‐MS, followed by the treatment of the MS data via exploratory statistical approaches, PCA (principal component analysis) and HCA (hierarchical clustering analysis). Ten distinct brands of each EV and ON olive oil, acquired at local stores, were analyzed by ESI(+)‐MS and the results from HCA and PCA clearly indicated the formation of two distinct groups related to these two categories. For the adulteration study, one brand of each olive oil grade (EV and ON) was selected. The counterfeit samples (a total of 20) were then prepared by adding assorted proportions, from 1 to 20% w/w, with increments of 1% w/w, of the ON to the EV olive oil. The PCA and HCA methodologies, applied to the ESI(+)‐MS data from the counterfeit (20) and authentic (10) EV samples, were able to readily detect adulteration, even at levels as low as 1% w/w. Copyright © 2010 John Wiley & Sons, Ltd.     

Structural characterization and identification of iridoid glycosides,saponins, phenolic acids and flavonoids in Flos Lonicerae Japonicae by a fast liquid chromatography method with diode‐array detection and time‐of‐flight mass spectrometry

A fast liquid chromatography method with diode‐array detection (DAD) and time‐of‐flight mass spectrometry (TOF‐MS) has been developed for analysis of constituents in Flos Lonicerae Japonicae (FLJ), a traditional Chinese medicine derived from the flower bud of Lonicera japonica. The chromatographic analytical time decreased to 25 min without sacrificing resolution using a column packed with 1.8‐µm porous particles (4.6 × 50 mm), three times faster than the performance of conventional 5.0‐µm columns (4.6 × 150 mm). Four major groups of compounds previously isolated from FLJ were structurally characterized by DAD‐TOF‐MS: iridoid glycosides showed maximum UV absorption at 240 nm; phenolic acids at 217, 242, and 326 nm; flavonoids at 255 and 355 nm; while saponins had no absorption. In electrospray ionization (ESI)‐TOF‐MS experiments, elimination of a glucose unit (162 Da), and successive losses of H₂O, CH₃OH and CO, were generally observed in iridoid glycosides; saponins were characterized by a series of identical aglycone ions; phenolic acids typically generated a base peak at [M–H–caffeoyl]^? by loss of a caffeic acid unit (162 Da) and several marked quinic acid moiety ions; cleavage of the glycosidic bond (loss of 162 or 308 Da), subsequent losses of H₂O, CO, RDA and C‐ring fragmentation were the most possible fragmentation pathways for flavonoids. By accurate mass measurements within 4 ppm error for each molecular ion and subsequent fragment ions, as well as the ‘full mass spectral’ information of TOF‐MS, a total of 41 compounds including 13 iridoid glycosides, 11 phenolic acids, 7 saponins, and 10 flavonoids were identified in a methanolic extract of FLJ. Copyright © 2009 John Wiley & Sons, Ltd.     

Rapid determination of oxidized methionine residues in recombinant human basic fibroblast growth factor by ultra‐performance liquid chromatography and electrospray ionization quadrupole time‐of‐flight mass spectrometry with in‐source collision‐induced dissociation

The primary structure of the deteriorated recombinant human basic fibroblast growth factor (rhbFGF) was determined by ultra‐performance liquid chromatography and electrospray ionization quadrupole time‐of‐flight mass spectrometry (UPLC/ESI‐QTOF‐MS) with in‐source collision‐induced dissociation (CID). The rhbFGFs before and after treatment with hydrogen peroxide (H₂O₂) were separated using an ACQUITY UPLC BEH300 C18 column (1.7 µm, 150 mm × 2.1 mm i.d.) with a gradient elution of a mixture of water/acetonitrile containing 0.1% formic acid. The separated proteins were then detected by a SYNAPT? High Definition Mass Spectrometry? system (SYNAPT‐MS). Two methionine (Met) residues in the rhbFGF structure were oxidized to Met‐sulfoxide (Met‐O) in 0.03% H₂O₂ at pH 2.0. As the result, three peaks, except for the peak of rhbFGF, appeared on the chromatogram. The three proteins corresponding to each peak were estimated as the denatured rhbFGFs including the Met‐O residue(s) with TOF‐MS. Furthermore, the position of the Met‐O residue(s) was efficiently identified by UPLC/ESI‐QTOF‐MS using the in‐source CID technique. The proposed method seems to be very useful for the structural elucidation of proteins, because the oxidized Met residues in rhbFGF were easily and rapidly identified. Copyright © 2009 John Wiley & Sons, Ltd.     

Evaluation of matrix effect in one‐dimensional and comprehensive two‐dimensional liquid chromatography for the determination of the phenolic fraction in extra virgin olive oils

Olea europaea, meaning “European olive,” is a small tree belonging to the family Oleaceae, occurring in the Mediterranean Basin. Olive oil is an essential component of a balanced diet because of its nutritional value. Among micronutrients, phenolic compounds did show important beneficial effects for human health. The majority of the research studies on the phenol content are carried out by liquid chromatography combined to photodiode array and/or mass spectrometry detection; however, because of matrix complexity, one‐dimensional liquid chromatography cannot be sometimes sufficient to obtain rewarding separations, requiring more advanced analytical techniques. In this work, comprehensive two‐dimensional liquid chromatography, incorporating RP‐Amide and C18 stationary phases, in the first and second dimension, respectively, both under reversed phase conditions, was investigated for the determination of the phenolic fraction in extra virgin olive oil samples. As far as detection is concerned, triple quadrupole mass spectrometry was employed under multi reaction monitoring mode offering superior selectivity and sensitivity. The reduction of matrix effects, when using comprehensive two‐dimensional liquid chromatography with respect to conventional one‐dimensional liquid chromatography, was assessed by comparing the slopes of calibration curves built from standard solutions and spiked olive oil samples.     

Characterization of phenolic compounds in green and red oak‐leaf lettuce cultivars by UHPLC‐DAD‐ESI‐QToF/MS using MSE scan mode

Lettuce (Lactuca sativa ) is one of the most popular leafy vegetables in the world and constitutes a major dietary source of phenolic compounds with health‐promoting properties. In particular, the demand for green and red oak‐leaf lettuces has considerably increased in the last years but few data on their polyphenol composition are available. Moreover, the usage of analytical edge technology can provide new structural information and allow the identification of unknown polyphenols. In the present study, the phenolic profiles of green and red oak‐leaf lettuce cultivars were exhaustively characterized by ultrahigh‐performance liquid chromatography (UHPLC) coupled online to diode array detection (DAD), electrospray ionization (ESI), and quadrupole time‐of‐flight mass spectrometry (QToF/MS), using the MS^E instrument acquisition mode for recording simultaneously exact masses of precursor and fragment ions. One hundred fifteen phenolic compounds were identified in the acidified hydromethanolic extract of freeze‐dried lettuce leaves. Forty‐eight of these compounds were tentatively identified for the first time in lettuce, and only 20 of them have been previously reported in oak‐leaf lettuce cultivars in literature. Both oak‐leaf lettuce cultivars presented similar phenolic composition, except for apigenin‐glucuronide and dihydroxybenzoic acid, only detected in the green cultivar; and for luteolin‐hydroxymalonylhexoside, an apigenin conjugate with molecular formula C₄₀H₅₄O₁₉ (monoisotopic MW = 838.3259 u ), cyanidin‐3‐O ‐glucoside, cyanidin‐3‐O ‐(3″‐O ‐malonyl)glucoside, cyanidin‐3‐O ‐(6″‐O ‐malonyl)glucoside, and cyanidin‐3‐O ‐(6″‐O ‐acetyl)glucoside, only found in the red cultivar. The UHPLC‐DAD‐ESI‐QToF/MS^E approach demonstrated to be a useful tool for the characterization of phenolic compounds in complex plant matrices.     

Alkylation of complementary ribonucleotides by 1,2‐dodecyl‐epoxide in a micellar environment: a liquid chromatography—electrospray ionization—sequential mass spectrometry investigation

Alkylation of a pair of complementary ribonucleotides, adenosine monophosphate (AMP) and uridine monophosphate (UMP), was accomplished by 1,2‐dodecyl‐epoxide (DE) in a oil‐in‐water microemulsion based on the cationic surfactant Cetyl‐trimethyl‐ammonium‐bromide, providing a suitable catalytic interface for the reagents. Several, often isomeric, alkylation products, bearing one or two hydroxy–dodecyl moieties on their structures, were identified in the reaction mixtures by high‐performance liquid chromatography coupled to electrospray ionization ion trap mass spectrometry. In particular, mass spectrometry (MS)/MS spectra, implemented by extracted ion chromatograms obtained for peculiar MS/MS product ions, indicated alkylation to occur on uracil and on uracil/phosphate OH groups in singly and doubly alkylated UMP, respectively. Adenine NH₂ group and phosphate or ribose OH groups were found to be involved as such (single alkylation) or in combination, in the case of alkylated derivatives of AMP. The reaction of both endocyclic N and C?O groups (tautomerized to C? OH groups) of uracil and the predominance of nucleophilic attack to the more accessible carbon of the DE epoxydic bridge (the only exception being the reaction by the NH₂ group of adenine) were inferred from MS³ spectra with the help of extracted ion chromatograms for specific fragment ions, after their structural characterization. Interestingly, alkylation on one of the uracil C?O groups and, partially, on the adenine NH₂ group, both potentially involved in AMP/UMP base pairing in the micellar environment, were found to be hindered when both ribonucleotides were present in the reaction mixtures. Copyright © 2009 John Wiley & Sons, Ltd.     

Identification of compounds from high‐fat and extra virgin olive oil‐supplemented diets in whole mouse liver extracts and isolated mitochondria using mass spectrometry

Nonalcoholic steatohepatitis (NASH) is a fatty liver disorder that could be improved with extra virgin olive oil (EVOO) supplementation in diet. We propose the monitoring, in whole mouse liver extracts and in isolated mitochondria, of the absorption of compounds from three different diets: standard (CT), high‐fat (HFD) and high‐fat supplemented with EVOO (HFSO). Male mice were submitted to one of the following three diets: CT or HFD for 16 weeks or HFD for 8 weeks followed by additional 8 weeks with HFSO. Following this period, liver was extracted for histological evaluation, mitochondria isolation and mass spectrometry analyses. Diets, liver extracts and Percoll‐purified mitochondria were analyzed using ESI‐MS and the lipidomics approach. Morphological, histological and spectrometric results indicated a decrease in NASH severity with EVOO supplementation in comparison with animals maintained with HFD. Spectrometric data also demonstrated that some compounds presented on the diets are absorbed by the mitochondria. EVOO was shown to be a potential therapeutic alternative in food for NASH. Our results are in accordance with the proposition that the major factor that influences different responses to diets is their composition – and not only calories – especially when it comes to studies on obesity. Copyright © 2015 John Wiley & Sons, Ltd.     

Fast determination of virgin olive oil phenolic metabolites in human high‐density lipoproteins

In recent years it has been confirmed that the consumption of olive oil prevents the oxidation of biomolecules owing to its monounsaturated fatty acids (MUFA) and phenolic content. The main objective of the study was to develop an ultra‐high‐performance liquid chromatography (UHPLC) tandem mass spectrometry (MS/MS) method for the determination of phenolic compounds in human high‐density lipoprotein (HDL) samples. At the same time, the influence of olive oil consumption on the phenolic metabolite levels was evaluated in a European population. The participants were 51 healthy men, aged 20–60. They were randomized to two consecutive intervention periods with the administration of raw olive oil with low and high polyphenolic content. The UHPLC‐MS/MS analytical method has been validated for hydroxytyrosol and homovanillic acid in terms of linearity (r² = 0.99 and 1.00), repeatability (5.7 and 6.5%) reproducibility (6.2 and 7%), recovery (98 to 97%), limits of detection (1.7 to 1.8 ppb) and quantification (5.8 and 6.3 ppb).The levels of the studied metabolites increased significantly after high polyphenolic content virgin olive oil ingestion (p <0.05) compared with lowpolyphenolic content olive oil. Virgin olive oil consumption increases the levels of phenolic metabolites in HDL and thus provides human HDL with more efficient antioxidant protection. Copyright © 2014 John Wiley & Sons, Ltd.     

Sensitized Lanthanide‐Ion Luminescence with Aryl‐Substituted N‐(2‐Nitrophenyl)acetamide‐Derived Chromophores

The syntheses of the two tetraazamacrocyclic ligands L1 and L2 bearing a [(methoxy‐2‐nitrophenyl)amino]carbonyl chromophore, i.e., an N‐(methoxy‐2‐nitrophenyl)acetamide moiety, together with their corresponding lanthanide‐ion complexes are described. A combined spectroscopic (UV/VIS, ¹H‐NMR), structural (X‐ray), and theoretical (DFT) investigation revealed that the absorption properties of the chromophores were dictated by the extent of electronic delocalisation, which in turn was determined by the position of the MeO substituent at the aromatic ring. X‐Ray crystallographic studies showed that when attached to the macrocycle, both isomeric forms of the N‐(methoxy‐2‐nitrophenyl)acetamide unit can participate in coordination, via the C?O, to an encapsulated potassium cation. Luminescence measurements confirmed that such a binding mode also exists in solution for the corresponding lanthanide complexes (q ca. ≤1), with the para‐MeO derivative allowing longer wavelength sensitization (λ_ex 330 nm).     

Isomer differentiation via collision‐induced dissociation: The case of protonated α‐, β2‐ and β3‐phenylalanines and their derivatives

A combination of electrospray ionisation (ESI), multistage and high‐resolution mass spectrometry experiments is used to examine the gas‐phase fragmentation reactions of the three isomeric phenylalanine derivatives, α‐phenylalanine, β²‐phenylalanine and β³‐phenylalanine. Under collision‐induced dissociation (CID) conditions, each of the protonated phenylalanine isomers fragmented differently, allowing for differentiation. For example, protonated β³‐phenylalanine fragments almost exclusively via the loss of NH₃, only β²‐phenylalanine via the loss of H₂O, while α‐ and β²‐phenylalanine fragment mainly via the combined losses of H₂O + CO. Density functional theory (DFT) calculations were performed to examine the competition between NH₃ loss and the combined losses of H₂O and CO for each of the protonated phenylalanine isomers. Three potential NH₃ loss pathways were studied: (i) an aryl‐assisted neighbouring group; (ii) 1,2 hydride migration; and (iii) neighbouring group participation by the carboxyl group. Finally, we have shown that isomer differentiation is also possible when CID is performed on the protonated methyl ester and methyl amide derivatives of α‐, β²‐ and β³‐phenylalanines. Copyright © 2010 John Wiley & Sons, Ltd.     

Fragmentation pathways and differentiation of positional isomers of sorafenib and structural analogues by ESI‐IT‐MSn and ESI‐Q‐TOF‐MS/MS coupled with DFT calculations

Sorafenib is an orally active multikinase inhibitor for the treatment of renal cell carcinoma. A series of sorafenib structural analogues were investigated in this work for their gas‐phase fragmentation behaviors using electrospray ionization ion trap mass spectrometry and quadrupole time‐of‐flight mass spectrometry in the positive mode. The possible fragmentation pathways were proposed based on ESI‐MS/MS data and theoretical calculation. Different from the typical α‐cleavage of amide, consecutive reactions that involved elimination of H₂O and CH₃NC were observed for 2‐pyridinecarboxamide derivatives, which were followed by the formation of a stabilized 7‐membered ring carbocation by loss of CO. Two possible protonation sites occurred at carbonyl oxygen atoms for aryl‐urea derivatives and the α‐cleavage of urea was the main fragmentation pathways, which was followed by the formation of stable benzo [d] oxazole ring characteristic to aryl‐urea derivatives. The relative abundance of characteristic fragment ions and the energy‐resolved breakdown curves were used to distinguish the 4 sets of positional isomers of sorafenib and analogues. The methodology and results of the present work would contribute to the chemical structure identification of other structural analogues and the potential impurities presented in active pharmaceutical ingredients and drug formulations.     

Electrospray ionization tandem mass spectrometric analysis of ent‐6,7‐seco‐kaurane diterpenoids from the Isodon species

Electrospray ionization tandem mass spectrometry (ESI‐MSⁿ) using an ion trap instrument and accurate mass measurement on a quadrupole time‐of‐flight (Q‐TOF) mass spectrometer has aided the structural characterization and differentiation of the enmein and spiro‐lactone types of ent‐6,7‐seco‐kaurane diterpenoids from Isodon species. The mass spectral fragmentation data from both techniques was compared to obtain the mass spectrometric fragmentation pathways of the ent‐6,7‐seco‐kaurane diterpenoids with high confidence. The analysis revealed that losses of CH₂O and CO₂ are the predominant process for the enmein type of ent‐kauranes in negative ion mode, and the loss of CO₂ is typical for the spiro‐lactone type in positive ion mode. In addition, compounds of the spiro‐lactone type with a conserved core structure but different substituent groups, such as acetyl, hydroxyl, and aldehyde moiety, resulted in diagnostic product ions by means of successive losses of AcOH, H₂O, and CO, respectively. The fragmentation knowledge will facilitate the analysis and identification of the ent‐6,7‐seco‐kauranes in future plant research. Copyright © 2008 John Wiley & Sons, Ltd.     

`Segmented' crystals solved using synchrotron radiation: (2S,3R,4S,5R)‐4‐(10,10‐dimethyl‐3,3‐dioxo‐3λ6‐thia‐4‐azatricyclo[5.2.1.01,5]decan‐4‐ylcarbonyl)‐2,6‐diphenylperhydropyrrolo[3,4‐c]pyrrole‐1,3‐dione

The title compound, C₂₉H₃₁N₃O₅S, forms needle‐shaped `segmented' crystals, thereby inhibiting successful single‐crystal data collection using conventional laboratory facilities. One crystallite of dimensions 0.15 × 0.03 × 0.01 mm yielded sufficent single‐crystal diffraction data on the Australian Synchrotron PX1 beamline. The two independent molecules in the asymmetric unit are nearly superimposable and show only minor conformational deviations from closely related compounds. The molecules pack using one N—H...O hydrogen bond and several phenyl C—H...O(=S), phenyl C—H...O(=C) and methylene C—H...O(=C) hydrogen bonds and weak C—H...π interactions.