GC‐MS of amaryllidaceous galanthamine‐type alkaloids

Galanthamine‐type alkaloids produced by plants of the Amaryllidaceae family are potent acetylcholinesterase inhibitors. One of them, galanthamine, has been marketed as a hydrobromide salt for the treatment of Alzheimer's disease. In the present work, gas chromatography with electron impact mass spectrometry (GC‐EIMS) fragmentation of 12 reference compounds isolated from various amaryllidaceous plants and identified by spectroscopic methods (1D and 2D nuclear magnetic resonance, circular dichroism, high‐resolution MS (HRMS) and EIMS) was studied by tandem mass spectrometry (GC‐MS/MS) and accurate mass measurements (GC‐HRMS). The studied compounds showed good peak shape and efficient GC separation with a GC‐MS fragmentation pattern similar to that obtained by direct insertion probe. With the exception of galanthamine‐N‐oxide and N‐formylnorgalanthamine, the galanthamine‐type compounds showed abundant [M]^+. and [M‐H]⁺ ions. A typical fragmentation pattern was also observed, depending on the substituents of the skeleton. Based on the fragmentation pathways of reference compounds, three other galanthamine‐type alkaloids, including 3‐O‐(2′‐butenoyl)sanguinine, which possesses a previously unelucidated structure, were identified in Leucojum aestivum ssp. pulchelum, a species endemic to the Balearic islands. GC‐MS can be successfully applied to Amaryllidaceae plant samples in the routine screening for potentially new or known bioactive molecules, chemotaxonomy, biodiversity and identification of impurities in pharmaceutical substances. Copyright © 2012 John Wiley & Sons, Ltd.     

Regioisomer characterization of triacylglycerols by non‐aqueous reversed‐phase liquid chromatography/electrospray ionization mass spectrometry using silver nitrate as a postcolumn reagent

Triacylglycerols (TAGs) provide a challenge for mass spectrometry (MS) analysis because of their complexity. In particular, for dietary, nutritional and metabolic purposes, the positional placement of fatty acids on the glycerol backbone of TAGs is a crucial aspect. To solve this problem, we have investigated the TAGs' fragmentation patterns using an ion trap mass spectrometer. A series of pure regioisomeric pairs of TAGs (POP/PPO, POO/OPO and OSO/SOO) were cationized by Ag⁺ after their separation by non‐aqueous reversed‐phase liquid chromatography (NARP‐LC) before MS to improve MS sensitivity. Electrospray ionization–MS (ESI‐MS) conditions were optimized in order to produce characteristic [M + Ag + AgNO₃]⁺ ions from each TAG, which were then fragmented to produce MS/MS spectra and then fragmented further to produce up to MS⁵ spectra. The observation of ions produced by LC‐MS⁵ of on‐line Ag⁺‐cationized TAG provided unambiguous information on the fatty acid distribution on the glycerol backbone. These strategies of MS to MS⁵ experiments were applied to identify components and to determine the regiospecificity of TAG within a complex mixture of lipids in natural oils. Copyright © 2010 John Wiley & Sons, Ltd.     

MALDI‐TOF mass spectrometry,an efficient technique for in situ detection and characterization of actinomycins

An extensive study of actinomycins was performed using matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐TOF MS). Actinomycins represent a well‐known family of peptidolactone chromopeptides with potent cytostatic and antibiotic properties. Using five well‐characterized streptomycete strains, we introduced MALDI‐TOF MS as an efficient technique for rapid in situ detection of actinomycins in surface extracts of cells picked from agar plates. By this procedure, actinomycin complexes can be investigated with high sensitivity and accuracy in a minimum of time. These studies were complemented by mass spectrometric investigation of actinomycins obtained from culture filtrate extracts and purified by high‐performance liquid chromatography to detect yet unknown actinomycin species. By feeding experiments, C‐demethyl‐actinomycins from Streptomyces chrysomallus and Streptomyces parvulus as well as hemi‐actinomycins from Streptomyces antibioticus lacking one of the two pentapeptide lactone rings were isolated and characterized as novel variants for structure–activity relationship studies. Structural characterization of the investigated actinomycins was performed by post source decay MALDI‐TOF MS. The specific features of the fragmentation patterns of the protonated and cationized forms of selected actinomycins were investigated in detail. Copyright © 2014 John Wiley & Sons, Ltd.     

Analysis of α‐acyloxyhydroperoxy aldehydes with electrospray ionization–tandem mass spectrometry (ESI‐MSn)

A series of α‐acyloxyhydroperoxy aldehydes was analyzed with direct infusion electrospray ionization tandem mass spectrometry (ESI/MSⁿ) as well as liquid chromatography coupled with the mass spectrometry (LC/MS). Standards of α‐acyloxyhydroperoxy aldehydes were prepared by liquid‐phase ozonolysis of cyclohexene in the presence of carboxylic acids. Stabilized Criegee intermediate (SCI), a by‐product of the ozone attack on the cyclohexene double bond, reacted with the selected carboxylic acids (SCI scavengers) leading to the formation of α‐acyloxyhydroperoxy aldehydes. Ionization conditions were optimized. [M + H]⁺ ions were not formed in ESI; consequently, α‐acyloxyhydroperoxy aldehydes were identified as their ammonia adducts for the first time. On the other hand, atmospheric‐pressure chemical ionization has led to decomposition of the compounds of interest. Analysis of the mass spectra (MS² and MS³) of the [M + NH₄]⁺ ions allowed recognizing the fragmentation pathways, common for all of the compounds under study. In order to get detailed insights into the fragmentation mechanism, a number of isotopically labeled analogs were also studied. To confirm that the fragmentation mechanism allows predicting the mass spectrum of different α‐acyloxyhydroperoxy aldehydes, ozonolysis of α‐pinene, a very important secondary organic aerosol precursor, was carried out. Spectra of the two ammonium cationized α‐acyloxyhydroperoxy aldehydes prepared with α‐pinene, cis‐pinonic acid as well as pinic acid were predicted very accurately. Possible applications of the method developed for the analysis of α‐acyloxyhydroperoxy aldehydes in SOA samples, as well as other compounds containing hydroperoxide moiety are discussed. Copyright © 2013 John Wiley & Sons, Ltd.     

Gas‐phase fragmentations of N‐methylimidazolidin‐4‐one organocatalysts

N‐methylimidazolidin‐4‐one organocatalysts were studied in the gas phase. Protonated and sodium‐cationized (sodiated) molecules are conveniently accessible by electrospray mass spectrometry. Protonation enables three different closed‐shell paths of ring cleavage leading to iminium ions. The fragmentation pattern is largely unaffected by exocyclic substituents and thus is valuable to characterize the substance type as N‐methylimidazolidin‐4‐ones. Sodiated species show a distinctly different fragmentation that is less useful for characterization purposes: apart from signal loss due to dissociation of Na⁺, the observation of benzyl radical loss is by far predominant. Only in absence of a benzyl substituent, an analogue of the third ring cleavage (loss of [C₂H₅NO]) is observed. Copyright © 2017 John Wiley & Sons, Ltd.     

Decameric uracil complexes around Li+

Electrospray ionization (ESI) in combination with mass spectrometry (MS) experiments were carried out to study decameric uracil complexes cationized with Li⁺ ion. A previous study has shown that, under specific experimental conditions, a particularly intense peak of the decamer U₁₀Li⁺ is formed, which was referred to as an indication for so‐called ‘magic number’ cluster. In order to gain more insight on the structure of this decameric complex, here, we report experimental studies concerning the kinetics of the fragmentation. In accordance with the new experimental data, structural models were constructed and fully optimized using ab initio and density functional theory quantum chemistry calculations. The theoretical study allowed us to propose a stable gas‐phase structure which is compatible with all experimental findings. Copyright © 2010 John Wiley & Sons, Ltd.     

Sodiation‐based in‐source collision for profiling of pyranocoumarins in Radix Peucedani (Qianhu): utility of sodium adducts' stability with in‐source collision

Full scan mode of liquid chromatography‐mass spectrometry equipped with an electrospray ionization source offers a chance on global detection of complicated components; however, the scan mode carries significant challenges in rapidly capturing information of analysts. Sodiation‐based in‐source collision was proposed here, as a technique for rapid detecting untargeted analytes in full scan analysis, which was based on the stability of sodium adducts and the nonselectivity of in‐source collision. Then the technique was applied to profile of angular‐type pyranocoumarins (APs) in Radix Peucedani, with full scan analysis performed at two specific in‐source collision energy: a high energy 50 V that is tolerated by the sodium adducts of APs, and a low energy 10 V, at which abundant adducts were offered. The spectra list of two average mass spectra was exported, and stable ions were selected based on the intensity ratio of standards at the two collision energy. Then 27 plausible [M + Na]⁺ m/z values of APs were acquired after filtering the fragment ion and isotope ions and validating with [M + NH₄]⁺. Eighty‐two APs finally were tentatively identified based on their accurate spectral data of MSⁿ, fragmentation rules, and elution order regardless of their absolute configuration, which included 25 reported APs from Peucedanum praeruptorum Dunn. The technique provided a novel application of sodium adduct in qualitative analysis. And it was valuable for rapidly capturing information of analytes in full scan analysis, not only for APs but also for other compounds that could form sodium adducts. Copyright © 2017 John Wiley & Sons, Ltd.     

Energy‐resolved technique for discovery and identification of malonyl‐triterpene saponins in Caulophyllum robustum by UHPLC‐electrospray Fourier transform mass spectrometry

Malonyl‐triterpene saponins (MTSs) attract scientific attentions because of their structural diversities and valuable bioactivities. However, its thermal instability brings a huge amount of challenges for isolation and purification of this class of compounds. To our best knowledge, there has been no report on isolation and analysis of MTSs from genus Caulophyllum. In this study, a strategy combining data acquisition using an energy‐resolved technique and the narrow widow extracted ion chromatograms as data mining method was developed for discovery and identification of MTSs in Caulophyllum robustum hair roots by ultra high liquid chromatography coupled to electrospray ionization Fourier transform mass spectrometry. The method was performed at an independent MS full scan using our bottom‐up energies by in‐source collision induced dissociations with 0, 25, 50 and 100 eV in both positive and negative modes. Precursor ion as well as fragment ion information was simultaneously collected from four energy‐resolved MS spectra in a single run of 18 min. The fragmentation pathways of intact deprotonated, protonated and sodium ions of MTSs were proposed for the structural elucidation of Caulophyllum MTSs. A flowchart involving a stepwise procedure based on key fragments from ESI^?/ESI⁺‐FT‐MS^{(1, 1)} to MS^{(1, 4)} spectra was constructed for the identification of structural elements in the MTSs. As a result, a total of 23 MTSs were discovered and tentatively identified, which had not been reported from Caulophyllum species before. All of these were potentially new compounds. This study provides an excellent example for discovery and identification of MTSs in herb medicines. Copyright © 2016 John Wiley & Sons, Ltd.     

Identification of substances migrating from plastic baby bottles using a combination of low‐resolution and high‐resolution mass spectrometric analysers coupled to gas and liquid chromatography

This work presents a strategy for elucidation of unknown migrants from plastic food contact materials (baby bottles) using a combination of analytical techniques in an untargeted approach. First, gas chromatography (GC) coupled to mass spectrometry (MS) in electron ionisation mode was used to identify migrants through spectral library matching. When no acceptable match was obtained, a second analysis by GC‐(electron ionisation) high resolution mass spectrometry time of flight (TOF) was applied to obtain accurate mass fragmentation spectra and isotopic patterns. Databases were then searched to find a possible elemental composition for the unknown compounds. Finally, a GC hybrid quadrupole‐TOF‐MS with an atmospheric pressure chemical ionisation source was used to obtain the molecular ion or the protonated molecule. Accurate mass data also provided additional information on the fragmentation behaviour as two acquisition functions with different collision energies were available (MS^E approach). In the low‐energy function, limited fragmentation took place, whereas for the high‐energy function, fragmentation was enhanced. For less volatile unknowns, ultra‐high pressure liquid chromatography‐quadrupole‐TOF‐MS was additionally applied. Using a home‐made database containing common migrating compounds and plastic additives, tentative identification was made for several positive findings based on accurate mass of the (de)protonated molecule, product ion fragments and characteristic isotopic ions. Six illustrative examples are shown to demonstrate the modus operandi and the difficulties encountered during identification. The combination of these techniques was proven to be a powerful tool for the elucidation of unknown migrating compounds from plastic baby bottles. Copyright © 2015 John Wiley & Sons, Ltd.     

Specificity enhancement by electrospray ionization multistage mass spectrometry – a valuable tool for differentiation and identification of ‘V’‐type chemical warfare agents

The use of chemical warfare agents has become an issue of emerging concern. One of the challenges in analytical monitoring of the extremely toxic ‘V’‐type chemical weapons [O‐alkyl S‐(2‐dialkylamino)ethyl alkylphosphonothiolates] is to distinguish and identify compounds of similar structure. MS analysis of these compounds reveals mostly fragment/product ions representing the amine‐containing residue. Hence, isomers or derivatives with the same amine residue exhibit similar mass spectral patterns in both classical EI/MS and electrospray ionization‐MS, leading to unavoidable ambiguity in the identification of the phosphonate moiety. A set of five ‘V’‐type agents, including O‐ethyl S‐(2‐diisopropylamino)ethyl methylphosphonothiolate (VX), O‐isobutyl S‐(2‐diethylamino)ethyl methylphosphonothiolate (RVX) and O‐ethyl S‐(2‐diethylamino)ethyl methylphosphonothiolate (VM) were studied by liquid chromatography/electrospray ionization/MS, utilizing a QTRAP mass detector. MS/MS enhanced product ion scans and multistage MS³ experiments were carried out. Based on the results, possible fragmentation pathways were proposed, and a method for the differentiation and identification of structural isomers and derivatives of ‘V’‐type chemical warfare agents was obtained. MS/MS enhanced product ion scans at various collision energies provided information‐rich spectra, although many of the product ions obtained were at low abundance. Employing MS³ experiments enhanced the selectivity for those low abundance product ions and provided spectra indicative of the different phosphonate groups. Study of the fragmentation pathways, revealing some less expected structures, was carried out and allowed the formulation of mechanistic rules and the determination of sets of ions typical of specific groups, for example, methylphosphonothiolates versus ethylphosphonothiolates. The new group‐specific ions elucidated in this work are also useful for screening unknown ‘V’‐type agents and related compounds, utilizing precursor ion scan experiments. Copyright © 2013 John Wiley & Sons, Ltd.     

两类三组份反应产物：1,3-恶嗪及嘧啶-2-酮类化合物的质谱学行为研究

电喷雾质谱被应用于分辨2-氨基-1,3-恶嗪及六氢化-4-苯基-吡喃[2,3-d]嘧啶-2-酮的杂环结构。两类化合物均为三组份反应的产物,且其杂环的结构很难用NMR判断。实验首次系统研究了两类化合物的质谱学行为（包括氘代实验和高分辨质谱研究）,发现前者在CID实验中丢失CH2N2和HCNO,而后者为直接丢失尿素。这些特征丢失为该类衍生物的结构判断,尤其是高通量的合成产物分析提供了重要的依据。     

The unusual fragmentation of long‐chain feruloyl esters under negative ion electrospray conditions

Long‐chain ferulic acid esters, such as eicosyl ferulate ( 1 ), show a complex and analytically valuable fragmentation behavior under negative ion electrospay collision‐induced dissociation ((?)‐ESI‐CID) mass spectrometry, as studied by use of a high‐resolution (Orbitrap) mass spectrometer. In a strong contrast to the very simple fragmentation of the [M + H]⁺ ion, which is discussed briefly, the deprotonated molecule, [M – H]^?, exhibits a rich secondary fragmentation chemistry. It first loses a methyl radical (MS²) and the ortho‐quinoid [M – H – Me]^‐? radical anion thus formed then dissociates by loss of an extended series of neutral radicals, C_nH_2n + 1^? (n = 0–16) from the long alkyl chain, in competition with the expulsion of CO and CO₂ (MS³). The further fragmentation (MS⁴) of the [M – H – Me – C₃H₇]^? ion, discussed as an example, and the highly specific losses of alkyl radicals from the [M – H – Me – CO]^‐? and [M – H – Me – CO₂]^‐? ions provide some mechanistic and structural insights.     

Relationship between Hammett's parameters and in silico density functional with tandem mass ESI‐CID fragmentation: Dihydropyridines as prototypes

Over the years, with the instrumental analysis evolution, the relationships between the carried‐out results with the data of theoretical analysis in silico and the Hammett's parameters have been reported. They have been very useful for chemical characterization of small organic molecules. Thus, this work aims at showing the feasibility and limitations for Hammett's and density functional theory applications in electrospray ionization–collision‐induced dissociation (ESI‐CID) fragmentation provision. For this, 13 dihydropyrimidinones para, meta, and orto monosubstituted were studied using ESI and CID in positive mode. As a result, it was observed that the main fragmentation includes the isocyanate and ethanol loses at low energy. Nevertheless, at higher energies, radical ions formed by McLafferty rearrangement were observed. The Hammett plots were correlated fragmentation profiles, showing good linearity for the [M + H]⁺, which does not occur to radical ions and carbocation's. These tendencies had demonstrated that the stability of protonate and activation energy of secondary ions changes with the pKa. The density functional theory studies indicated that, both nitrogen atoms in the dihydropyrimidinone's prototypes are capable of being protonated. However, the activation energy of fragmentation products is not changed. Therefore, this work has shown information, which can be useful to understand tandem mass spectrometry in ESI‐CID conditions for small organic molecules series. This is the first step for normalization of fragmentation pathway.     

Metabolic profiles of dioscin in rats revealed by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry

Dioscin (DIS), one of the most abundant bioactive steroidal saponins in Dioscorea sp., is used as a complementary medicine to treat coronary disease and angina pectoris in China. Although the pharmacological activities and pharmacokinetics of DIS have been well demonstrated, information regarding the final metabolic fates is very limited. This study investigated the in vivo metabolic profiles of DIS after oral administration by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry method. The structures of the metabolites were identified and tentatively characterized by means of comparing the molecular mass, retention time and fragmentation pattern of the analytes with those of the parent compound. A total of eight metabolites, including seven phase I and one phase II metabolites, were detected and tentatively identified for the first time. Oxidation, deglycosylation and glucuronidation were found to be the major metabolic processes of the compound in rats. In addition, a possible metabolic pathway on the biotransformation of DIS in vivo was proposed. This study provides valuable and new information on the metabolism of DIS, which will be helpful for further understanding its mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd.     

Identification of the unknown transformation products derived from lincomycin using LC‐HRMS technique

In this paper, a comprehensive study of the fate of an antibiotic, lincomycin, in the aquatic environment is presented. High‐resolution mass spectrometry was employed to assess the evolution of the process over time. Formation of intermediate compounds was followed by high performance liquid chromatography‐high resolution mass spectrometry (LC‐HRMS); accurate mass‐to‐charge ratios of parent ions were reported with inaccuracy below 1 mmu, which guarantee the correct assignment of their molecular formula in all cases, while their MS² and MS³ spectra showed several structural‐diagnostic ions that allowed to characterize the different transformation products (TPs) and to discriminate the isobaric species. The simulation of phototransformation occurring in the aquatic environment and the identification of biotic and abiotic TPs of the pharmaceutical compound were carried out in different experimental conditions: dark experiments, homogeneous photolysis and heterogeneous photocatalysis using titanium dioxide, in order to recreate conditions similar to those found in the environment. Twenty‐one main species were identified afterwards lincomycin transformation. Several isomeric species were formed and characterized by analyzing MS and MSⁿ spectra and by comparison with parent molecule fragmentation pathways. The major transformation process for lincomycin is hydroxylation either at N‐alkyl side chain or at the pyrrolidine moiety. In addition, oxidation/reduction, demethylation or cleavage of pyranose ring occurs. Based on this information and additional assessment of profiles over time of formation/disappearance of each species, it was possible to recognize the transformation pathways followed by the drug. Copyright © 2012 John Wiley & Sons, Ltd.     

HPLC‐ESI‐MS/MS of brain neurotransmitter modulator lobeline and related piperidine alkaloids in Lobelia inflata L

There is a renewed interest in lobelia alkaloids because of their activity on the central nervous system. Lobeline, the most active of them, a nicotinic receptor ligand and neurotransmitter transporter inhibitor, is a candidate pharmacotherapy for metamphetamine abuse. In the present work, high‐performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry in positive ion mode was used for investigating the alkaloid profile in Lobelia inflata L. Chromatographic separations were achieved on a Gemini C6‐phenyl reversed‐phase column providing good peak shape and improved selectivity. Being mostly 2,6‐disubstituted piperidines, lobelia alkaloids presented abundant [M + H]⁺ ions with typical fragmentation. Identification was possible from a few specific ions, especially those resulting from excision of one of the substituents. Based on fragmentation pattern of lobeline as reference compound, 52 alkaloids were identified in the aqueous methanolic extract of L. inflata in contrast to the previously known some 20. Structural variability of these alkaloids identified arises basically from their substituents which can be phenyl‐2‐ketoethyl‐ or phenyl‐2‐hydroxyethyl units as well as their methyl‐, ethyl‐ or propyl‐ homologues attached in different combinations. Several propyl homologue lobelia alkaloids and five hydroxypiperidine derivatives were found in the plant at the first time. In addition to 8‐O‐esters of 2‐monosubstituted piperidine alkaloids previously reported by us in L. inflata, a 3‐hydroxy‐3‐phenylpropanoic acid ester of hydroxyallosedamine ring‐substituted was also identified as a new natural product. High‐performance liquid chromatography‐electrospray ionization tandem mass spectrometry can be successfully applied to Lobeliacae plant samples in the routine screening for new and known bioactive constituents, quality control of the crude drug, lobelia herba, alkaloid production studies, breeding and chemotaxonomy. Copyright © 2015 John Wiley & Sons, Ltd.     

Modified proton transfer reaction mass spectrometry (PTR‐MS) operating conditions for in vitro and in vivo analysis of wine aroma

With proton transfer reaction‐mass spectrometry standard operating conditions, analysis of alcoholic beverages is an analytical challenge. Ethanol reacts with the primary ion H₃O⁺ leading to its depletion and to formation of ethanol‐related ions and clusters, resulting in unstable ionization and in significant fragmentation of analytes. Different methods were proposed but generally resulted in lowering the sensitivity and/or complicating the mass spectra. The aim of the present study was to propose a simple, sensitive, and reliable method with fragmentation as low as possible, linearity within a realistic range of volatile organic compounds concentrations, and applicability to in vivo dynamic aroma release (nosespace) studies of wines. For in vitro analyses, a reference flask containing a hydro‐alcoholic solution (10% ethanol) was permanently connected to the PTR‐MS inlet in order to establish ethanol chemical ionization conditions. A low electric field strength to number density ratio E/N (80 Td) was used in the drift‐tube. A stable reagent ion distribution was obtained with the primary protonated ethanol ion C₂H₅OH₂⁺ accounting for more than 80% of the ionized species. The ethanol dimer (C₂H₅OH)₂H⁺ accounted for only 10%. Fragmentation of some aroma molecules important for white wine flavor (various esters, linalool, cis‐rose oxide, 2‐methylpropan‐1‐ol, 3‐methylbutan‐1‐ol, and 2‐phenylethanol) was studied from same ethanol content solutions connected alternatively with the reference solution to the instrument inlet. Linear dynamic range and limit of detection (LOD) were determined for ethyl hexanoate. Fragmentation of the protonated analytes was limited to a few ions of low intensity, or to specific fragment ions with no further fragmentation. Association and/or ligand switching reactions from ethanol clusters were only significant for the primary alcohols. Interpretation of the mass spectra was straightforward with easy detection of diagnostic ions. These results made this ethanol ionization method suitable for direct headspace analyses of model wines and to their nosespace analyses.     

Rapid screening and identification of lycodine‐type alkaloids in Lycopodiaceae and Huperziaceae plants by ultra‐performance liquid chromatography coupled with quadrupole time‐of‐flight mass spectrometry

Lycodine‐type alkaloids have gained significant interest owing to their unique skeletal characteristics and acetylcholinesterase activity. This study established a rapid and reliable method using ultra‐performance liquid chromatography coupled with electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry (UPLC‐ESI‐Q/TOF‐MS/MS) for comprehensive characterization of lycodine‐type alkaloids for the first time. The lycodine‐type alkaloids were detected successfully from Lycopodiastrum casuarinoides, Huperzia serrata and Phlegmarirus carinatus in seven plants of the Lycopodiaceae and Huperziaceae families, based on the established characteristic MS fragmentation of five known alkaloids. Furthermore, a total of 13 lycodine‐type alkaloids were identified, of which three pairs of isomers were structurally characterized and differentiated. This study further improves mass analysis of lycodine‐type alkaloids and demonstrates the superiority of UPLC with a high‐resolution mass spectrometer for the rapid and sensitive structural elucidation of other trace active compounds. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

Fragmentation pathways of metopimazine and its metabolite using ESI‐MSn,HR‐MS and H/D exchange

Metopimazine (MPZ) is a phenothiazine derivative used to prevent emesis during chemotherapy where few structural analysis of the aforementioned compound have been described in the literature. Thus, this work reports, for the first time, the detailed study of fragmentation pathways of MPZ and its metabolite (AMPZ) using electrospray ionization (EI) with multistage mass spectrometry (ESI‐MSⁿ) in positive‐ion mode. The structures of 21 product ions were identified and their accurate masses were determined using high resolution mass spectrometry (HRMS) experiments. Characteristic product ions of these two phenothiazine derivatives are more particularly displayed along with differences between their relative abundances and their structures checked by H/D exchange experiments. Copyright © 2010 John Wiley & Sons, Ltd.