Mass Spectrometric Fragmentation Patterns Research Articles

Comparative metabolite analysis of Piper sarmentosum organs approached by LC–MS-based metabolic profiling

Piper sarmentosum Roxb. (Piperaceae) is a traditional medicinal and food plant widely distributed in the tropical and subtropical regions of Asia, offering both health and culinary benefits. In this study the secondary metabolites in different organs of P. sarmentosum were identified and their relative abundances were characterized. The metabolic profiles of leaves, roots, stems and fruits were comprehensively investigated by liquid chromatography high-resolution mass spectrometry (LC-HR-MS) and the data subsequently analyzed using multivariate statistical methods. Manual interpretation of the tandem mass spectrometric (MS/MS) fragmentation patterns revealed the presence of 154 tentatively identified metabolites, mostly represented by alkaloids and flavonoids. Principle component analysis and hierarchical clustering indicated the predominant occurrence of flavonoids, lignans and phenyl propanoids in leaves, aporphines in stems, piperamides in fruits and lignan-amides in roots. Overall, this study provides extensive data on the metabolite composition of P. sarmentosum, supplying useful information for bioactive compounds discovery and patterns of their preferential biosynthesis or storage in specific organs. This can be used to optimize production and harvesting as well as to maximize the plant’s economic value as herbal medicine or in food applications.Graphical

Cysteine-free cone snail venom peptides: Classification of precursor proteins and identification of mature peptides.

The cysteine-free acyclic peptides present in marine cone snail venom have been much less investigated than their disulfide bonded counterparts. Precursor protein sequences derived from transcriptomic data, together with mass spectrometric fragmentation patterns for peptides present in venom duct tissue extracts, permit the identification of mature peptides. Twelve distinct gene superfamiles have been identified with precursor lengths between 64 and 158 residues. In the case of Conus monile, three distinct mature peptides have been identified, arising from two distinct protein precursors. Mature acyclic peptides are often post-translationally modified, with C-terminus amidation, a feature characteristic of neuropeptides. In the present study, 20 acyclic peptides from Conus monile and Conus betulinus were identified. The common modifications of C-terminus amidation, gamma carboxylation of glutamic acid (E to ϒ), N-terminus conversion of Gln (Q) to a pyroglutamyl residue (Z), and hydroxylation of Pro (P) to Hyp (O) are observed in one or more peptides identified in this study. Proteolytic trimming of sequences by cleavage at the C-terminus of Asn (N) residues is established. The presence of an asparagine endopeptidase is strengthened by the identification of legumain-like sequences in the transcriptome assemblies from diverse Conus species. Such sequences may be expected to have a cleavage specificity at Asn-Xxx peptide bonds.

Elucidation of the environmental reductive metabolism of the herbicide tritosulfuron assisted by electrochemistry and mass spectrometry

The environmental impact of pesticides and other pollutants is, to a great extent, determined by degradation and accumulation processes. Consequently, degradation pathways of pesticides have to be elucidated before approval by the authorities. In this study, the environmental metabolism of the sulfonylurea-herbicide tritosulfuron was investigated using aerobic soil degradation studies, during which a previously unidentified metabolite was observed using high performance liquid chromatography and mass spectrometry. The new metabolite was formed by reductive hydrogenation of tritosulfuron but the isolated amount and purity of the substance were insufficient to fully elucidate its structure. Therefore, electrochemistry coupled to mass spectrometry was successfully applied to mimic the reductive hydrogenation of tritosulfuron. After demonstrating the general feasibility of electrochemical reduction, the electrochemical conversion was scaled up to the semi-preparative scale and 1.0 mg of the hydrogenated product was synthesized. Similar retention times and mass spectrometric fragmentation patterns proved that the same hydrogenated product was formed electrochemically and in soil studies. Using the electrochemically generated standard, the structure of the metabolite was elucidated by means of NMR spectroscopy, which shows the potential of electrochemistry and mass spectrometry in environmental fate studies.

Chromatographic separation of tiropramide hydrochloride and its degradation products along with their structural characterization using LC-QTOF-MS/MS and NMR.

Tiropramide HCl, an antispasmodic drug was subjected to various stress conditions (hydrolytic, oxidative, photolytic and thermal) as per ICH guidelines. The drug is widely used as an antispasmodic agent but there were no comprehensive degradation studies reported on it. Hence, forced degradation studies of tiropramide HCl were carried out to establish the degradation profile and the storage conditions to maintain its quality attributes during the shelf life and usage. A selective HPLC method was developed to separate the drug as well as its degradation products using Agilent C18 (250×4.6 mm; 5 μm) column. The mobile phase of 10mM ammonium formate at pH 3.6 (solvent A) and methanol (solvent B) with gradient elution at a flow rate of 1.00 mL/min was used. Tiropramide was susceptible to acidic, basic hydrolytic exposure and oxidative stress conditions in the solution. This drug was found to be stable in neutral, thermal and photolytic conditions in both solution and solid-state. Five degradation products were detected under different stress conditions. The mass spectrometric fragmentation pattern of tiropramide and its degradation products was extensively studied using LC-Q-TOF-MS/MS for their structural characterization. The position of the oxygen atom in the N-oxide degradation product was confirmed by NMR studies. The knowledge gained by these studies was used to predict drug degradation profiles which will be helpful in analysing any impurities in dosage form.

Identification of 24-O-β-d-Glycosides and 7-Deoxy-Analogues of Okadaic Acid and Dinophysistoxin-1 and -2 in Extracts from Dinophysis Blooms, Dinophysis and Prorocentrum Cultures, and Shellfish in Europe, North America and Australasia.

Two high-mass polar compounds were observed in aqueous side-fractions from the purification of okadaic acid (1) and dinophysistoxin-2 (2) from Dinophysis blooms in Spain and Norway. These were isolated and shown to be 24-O-β-d-glucosides of 1 and 2 (4 and 5, respectively) by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and enzymatic hydrolysis. These, together with standards of 1, 2, dinophysistoxin-1 (3), and a synthetic specimen of 7-deoxy-1 (7), combined with an understanding of their mass spectrometric fragmentation patterns, were then used to identify 1–5, the 24-O-β-d-glucoside of dinophysistoxin-1 (6), 7, 7-deoxy-2 (8), and 7-deoxy-3 (9) in a range of extracts from Dinophysis blooms, Dinophysis cultures, and contaminated shellfish from Spain, Norway, Ireland, Canada, and New Zealand. A range of Prorocentrum lima cultures was also examined by liquid chromatography–high resolution tandem mass spectrometry (LC–HRMS/MS) and was found to contain 1, 3, 7, and 9. However, although 4–6 were not detected in these cultures, low levels of putative glycosides with the same exact masses as 4 and 6 were present. The potential implications of these findings for the toxicology, metabolism, and biosynthesis of the okadaic acid group of marine biotoxins are briefly discussed.

Breakdown of 3-(allylsulfonio)propanoates in bacteria from the Roseobacter group yields garlic oil constituents.

Two analogues of 3-(dimethylsulfonio)propanoate (DMSP), 3-(diallylsulfonio)propanoate (DAllSP), and 3-(allylmethylsulfonio)propanoate (AllMSP), were synthesized and fed to marine bacteria from the Roseobacter clade. These bacteria are able to degrade DMSP into dimethyl sulfide and methanethiol. The DMSP analogues were also degraded, resulting in the release of allylated sulfur volatiles known from garlic. For unknown compounds, structural suggestions were made based on their mass spectrometric fragmentation pattern and confirmed by the synthesis of reference compounds. The results of the feeding experiments allowed to conclude on the substrate tolerance of DMSP degrading enzymes in marine bacteria.

Metabolic profile of curcumin self‐emulsifying drug delivery system in rats determined by ultra‐high performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry

Curcumin (Cur) is a natural anticancer pigment, but its poor absorption and extensive metabolism limit its clinical applications. In this study, an ultra-high performance liquid chromatography/quadrupole time-of-flight mass spectrometry method was employed to investigate the metabolic profiles of a Cur self-emulsifying drug delivery system (C-SEDDS) in rat plasma, urine, bile and feces after oral administration at 100 mg/kg. Protein precipitation, solid-phase and ultrasonic extractions were used to prepare different biosamples. A total of 34 metabolites were identified using available reference standards, or tentatively identified based on the mass spectrometric fragmentation patterns and the chromatographic elution order. Nine metabolites of Cur were found for the first time in vivo. Glucuronidation, sulfation, reduction, dehydroxylation, demethylation, demethoxylation and methylation were its possible metabolic reactions. Moreover, the differences were compared in terms of plasma metabolites found in C-SEDDS-treated, Cur suspension-treated and rats treated with a commercial curcuminoid phospholipid complex administered at the same oral dose. Dihydrocurcumin (DHC), DHC glucuronide and methylated DHC were found only in the metabolic profile of C-SEDDS-treated rat plasma, suggesting that different drug delivery systems may cause a change in Cur metabolic pathways. This study provides a sensitive and rapid method for the identification of Cur metabolites in biosamples.

Rapid Preparation of a Large Sulfated Metabolite Library for Structure Validation in Human Samples.

Metabolomics analysis of biological samples is widely applied in medical and natural sciences. Assigning the correct chemical structure in the metabolite identification process is required to draw the correct biological conclusions and still remains a major challenge in this research field. Several metabolite tandem mass spectrometry (MS/MS) fragmentation spectra libraries have been developed that are either based on computational methods or authentic libraries. These libraries are limited due to the high number of structurally diverse metabolites, low commercial availability of these compounds, and the increasing number of newly discovered metabolites. Phase II modification of xenobiotics is a compound class that is underrepresented in these databases despite their importance in diet, drug, or microbiome metabolism. The O-sulfated metabolites have been described as a signature for the co-metabolism of bacteria and their human host. Herein, we have developed a straightforward chemical synthesis method for rapid preparation of sulfated metabolite standards to obtain mass spectrometric fragmentation pattern and retention time information. We report the preparation of 38 O-sulfated alcohols and phenols for the determination of their MS/MS fragmentation pattern and chromatographic properties. Many of these metabolites are regioisomers that cannot be distinguished solely by their fragmentation pattern. We demonstrate that the versatility of this method is comparable to standard chemical synthesis. This comprehensive metabolite library can be applied for co-injection experiments to validate metabolites in different human sample types to explore microbiota-host co-metabolism, xenobiotic, and diet metabolism.

Combination of MS Binding Assays and affinity selection mass spectrometry for screening of structurally homogenous libraries as exemplified for a focused oxime library addressing the neuronal GABA transporter 1.

This study presents an efficient screening approach based on combination of mass spectrometry (MS) based binding assays (MS Binding Assays) and affinity selection mass spectrometry (ASMS) customized for screening of structurally homogeneous libraries sharing a common mass spectrometric fragmentation pattern. After reaction of a nipecotic acid derivative possessing a hydroxylamine functionality with aldehydes, the resulting oxime library was screened accordingly toward the GABA transporter subtype 1 (GAT1), a drug target for several neurological disorders. After assessing sublibraries' activities for inhibition of reporter ligand binding, hits in active ones were directly identified. This could be achieved by recording mass transitions for the reporter ligand as well as those predicted for the library components in a single LC-MS/MS run with a triple quadrupole mass spectrometer in the multiple reaction monitoring mode. Identification of hits with a predefined affinity could be reliably accomplished by calculation of IC50-values from specific binding concentrations of library constituents and reporter ligand. Application of this strategy revealed six hits, from which two of them were resynthesized for further biological evaluation. Thereby, the best one displayed a pKi of 7.38 in MS Binding Assays and a pIC50 of 6.82 in [3H]GABA uptake assays for GAT1.

Identification of secondary metabolites in Tripterygium wilfordii hairy roots and culture optimization for enhancing wilforgine and wilforine production

Hairy roots culture is an effective biological system to solve the shortage of natural resources of Tripterygium wilfordii for the production of the important secondary metabolites. However, there is no enough information about the secondary metabolites in Tripterygium wilfordii hairy root cultures. The present study identified the secondary metabolites in T. wilfordii hairy roots by high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS). Subsequently, the nitrogen source and phosphate concentration were optimized to enhance the production of the major active compounds wilforgine and wilforine. Nine compounds including triptolide, wilforgine, wilforine, and so on were identified according to their retention behavior in liquid chromatography and mass spectrometric fragmentation patterns. The Murashige and Skoog (MS) medium was modified for enhancing wilforgine and wilforine production in T. wilfordii hairy root cultures by altering the ratio of NH4+/NO3－and the concentration of phosphate. The results showed that 10:50 mM NH4+/NO3－ and 0.3125 mM phosphate were optimal for roots growth and the production of wilforgine and wilforine. After 35 days of cultivation in the modified MS medium containing 10:50 mM NH4+/NO3－ and 0.3125 mM phosphate, the maximum production of wilforgine and wilforine was up to 1509.87 μg·flask−1 and 578.56 μg·flask−1 in T. wilfordii hairy roots separately, a 42 % and 48 % increase over that in the basic MS medium. The present study laid a foundation for the large-scale production of secondary metabolites from T. wilfordii hairy roots.

Mass spectrometric fragmentation patterns discriminate C1- and C4-oxidised cello-oligosaccharides from their non-oxidised and reduced forms

Lytic polysaccharide monooxygenases (LPMOs) are powerful enzymes that degrade recalcitrant polysaccharides, such as cellulose. However, the identification of LPMO-generated C1- and/or C4-oxidised oligosaccharides is far from straightforward. In particular, their fragmentation patterns have not been well established when using mass spectrometry. Hence, we studied the fragmentation behaviours of non-, C1- and C4-oxidised cello-oligosaccharides, including their sodium borodeuteride-reduced forms, by using hydrophilic interaction chromatography and negative ion mode collision induced dissociation - mass spectrometry. Non-oxidised cello-oligosaccharides showed predominantly C- and A-type cleavages. In comparison, C4-oxidised ones underwent B-/Y- and X-cleavage close to the oxidised non-reducing end, while closer to the reducing end C-/Z- and A-fragmentation predominated. C1-oxidised cello-oligosaccharides showed extensively A-cleavage. Reduced oligosaccharides showed predominant glycosidic bond cleavage, both B-/Y- and C-/Z-, close to the non-reducing end. Our findings provide signature mass spectrometric fragmentation patterns to unambiguously elucidate the catalytic behaviour and classification of LPMOs.

Benzoylfentanyl and parafluorobutyrfentanyl: Some analytical and metabolism data

Summary Today, New Psychoactive Substances (NPS) are increasingly being related to post-mortem cases, and this problem drastically intensifies as a result of the New Synthetic Opioids (NSOs) surge. Among NSOs, fentanyl derivatives (FDs) consist in a myriad of drugs with a high turnover. FDs detection in human biological samples is complicated by low concentrations and usual extensive metabolism. In this challenging context, this manuscript aims to report analytical data about two poorly documented FDs: benzoylfentanyl (BZF) and parafluorobutyrfentanyl (pFBF). In 2018, these FDs were identified in three samples (powders and blotting papers) in France. Nuclear magnetic resonance and liquid chromatography with high-resolution mass spectrometry detection (LC-HRMS) data including observed mass spectrometric fragmentation patterns were obtained. In addition, metabolites were investigated using human liver microsomes incubations and LC-HRMS analysis: norBZF, despropionylfentanyl and a hydroxylated-BZF were identified (and observed in hair) as BZF metabolites; norpFBF, parafluorofentanyl and a hydroxylated-pFBF were identified as pFBF metabolites. In the worrisome context of NSOs detection, these preliminary data can be useful for toxicologists.

UPLC‐Q‐TOF‐MS/MS‐guided dereplication of Pulsatilla chinensis to identify triterpenoid saponins

Triterpenoid saponins are the major bioactive constituents of Pulsatilla chinensis, playing an important role in various biological activities such as anti-tumour, cognition-enhancing, anti-biosis, anti-inflammatory, hypoglycemic and immunological adjuvant. To establish a systematic strategy based on ultra-high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS) for the efficient characterisation and identification of triterpenoid saponins in crude extracts from Pulsatilla chinensis. In this work, the strategy includes two aspects: (1) positive mode: by target screening, we can deduce the aglycone type and the composition of sugar moiety according to the fragment ions; untargeted screening includes four steps, find unknown, formula finder, ChemSpider search and MS/MS identification; (2) negative mode: according to the MS/MS spectra, the composition of sugar chain bonded to C-28 is inferred reasonably. The extract of Pulsatilla chinensis was separated within 60min on a C18 column and eluted with methanol and water both containing 0.1% formic acid. As a result, a total of 22 triterpenoid saponins (11 pairs of isomers) with four aglycone skeletons were tentatively identified or elucidated in crude extracts from Pulsatilla chinensis based on their retention times, the mass spectrometric fragmentation patterns, and MS and MS/MS data. This study provides an efficient analysis strategy to rapidly identify the triterpenoid saponins in Pulsatilla species even in traditional Chinese medicines.

Precursor Ion-Scan Mode-Based Screening Strategy for New Amorfrutin Derivatives from Amorpha fruticosa by UPLC–QqQ–MS and UPLC–Q-TOF–MS

This study presents a screening strategy for unknown compounds by coupling UPLC–QqQ–MS and UPLC–Q-TOF–MS analyses. Amorfrutins, potential PPARγ agonists in Amorpha fruticosa, were selected as the research target. First, MS/MS analysis of three amorfrutin references (AA, AB, and AC) by Q-TOF revealed the mass-spectrometric fragmentation patterns of amorfrutins, and m/z 225 was recognized as a characteristic and common fragment ion of amorfrutins. Then, unknown amorfrutins were screened in the fruits of A. fruticosa by UPLC–QqQ–MS operating in precursor ion-scan mode, and the product ion was set as m/z 225 for screening potential amorfrutins. According to the high-resolution MS–MS spectral data provided by UPLC–Q-TOF–MS, the molecular formula of potential amorfrutins and their respective characteristic fragments were calculated. Finally, three unknown amorfrutins, namely, amorfrutin D and two new amorfrutins, were identified. As far as we know, this is the first study to rapidly identify unknown compounds by combined application of QqQ–MS precursor ion scan and Q-TOF–MS formula calculation. This research strategy will also be effective for the discovery of other trace natural products and metabolites.

20α- and 20β-dihydrocortisone may interfere in LC-MS/MS determination of cortisol in saliva and urine

Background LC-MS/MS methods offer high selectivity in cortisol determinations. However, endogenous steroid metabolites may still interfere and compromise the results, for example in the diagnosis of Cushing's syndrome. Erroneously elevated cortisol may, in particular, be misleading at the low concentrations found in salivary samples obtained at late night and after dexamethasone suppression. Methods Interferences in our LC-MS/MS method used for determination of cortisol in saliva and urine were identified by comparing their retention times and mass spectra with those of pure candidate substances. The chromatographic conditions used in our LC-MS/MS method, including column and mobile phase gradient, were varied in order to separate the target compound from the interferences. Results Two interferences, which were co-eluting or eluting close to cortisol in our original method, were successfully separated from cortisol by adjustment of the chromatographic conditions. These interferences were found in both urine and saliva and were identified as the two endogenous cortisol isomers 20α- and 20β-dihydrocortisone. The isomers share molecular mass and mass spectrometric fragmentation pattern with cortisol using electrospray ionization in the positive-ion mode. Both give rise to the transitions m/z 363.1>121.1, 363.1>115.1 and 363.1>97.1. In our original LC-MS/MS setup, the 20β-dihydrocortisone co-eluted with cortisol in the chromatography step resulting in false high determinations. Conclusions Cortisol determination by LC-MS/MS may suffer from erroneously elevated results unless 20α- and 20β-dihydrocortisone are chromatographically separated from cortisol.

CYP1A1-Mediated Intramolecular Rearrangement of Aminoazepane in GDC-0339.

GDC-0339 is a novel small molecule pan-Pim kinase inhibitor that was discovered as a potential treatment of multiple myeloma. During the in vitro and in vivo metabolite profiling of GDC-0339, a metabolite was detected that had the same elemental composition as the parent but was distinct with respect to its chromatographic separation and mass spectrometric fragmentation pattern. High resolution tandem mass spectrometry data indicated the metabolite was modified at the aminoazepane moiety. The structure was solved by nuclear magnetic resonance analysis of the isolated metabolite and further confirmed by comparing it to a synthetic standard. These results indicated that the metabolite was formed by an intramolecular amine replacement reaction with the primary amine forming a new attachment to pyrazole without any change in stereochemistry. In vitro experiments showed cytochrome P450s catalyzed the reaction and demonstrated high isoform selectivity by CYP1A1. Results from kinetic experiments showed that the CYP1A1-mediated rearrangement of GDC-0339 was an efficient reaction with apparent turnover number (kcat) and Michaelis constant (Km) of 8.4 minutes-1 and 0.6 μM, respectively. The binding of GDC-0339 to the cytochrome P450 active site was examined by characterizing the direct inhibition of CYP1A1-mediated phenacetin O-deethylation, and GDC-0339 was a potent competitive inhibitor with Ki of 0.9 μM. This high affinity binding was unexpected given a narrow active site for CYP1A1 and GDC-0339 does not conform structurally to known CYP1A1 substrates, which are mostly polyaromatic planar molecules. Further, we explored some of the structural requirements for the rearrangement reaction and identified several analogs to GDC-0339 that undergo this biotransformation.

Bioactivity evaluation-based ultra high-performance liquid chromatography coupled with electrospray ionization tandem quadrupole-time-of-flight mass spectrometry and novel distinction of multi-subchemome compatibility recognition strategy with Astragali Radix-Fructus Corni herb-pair as a case study

The approach to investigate traditional Chinese medicine (TCM) is still in its infancy and has been facing enormous challenge. In this paper, a generally applicable strategy was developed for investigation on TCM systematically with an introduced interesting idea about a novel research system which called subchemome. A representative herb-pair, Astragali Radix-Fructus Corni, was successfully employed to expound this novel strategy. Firstly, subchemomes were prepared individually by applying the suitable column chromatography, each of them was detected by UV spectrophotometer or HPLC-DAD detector. The components in each part were then identified based on the mass spectrometric fragmentation patterns and tandem mass spectrometric data by using UHPLC-Q-TOF-MS. Using renal mesangial cell (RMC) viability assay as the evaluation of the pharmacological activity of each group, we developed the new mini herbal formulae aimed at diabetic nephropathy and identified fifteen marker components between the group of new mini herbal formulae and other groups from the angle of the constituent, and then explored the effects of new mini herbal formulae from another angle of the molecular mechanism. Overall, the presently developed strategy should be beneficial and widely used in the investigation on TCM from a new perspective.

Analytical Profiling of Bioactive Phenolic Compounds in Argan (Argania spinosa) Leaves by Combined Microextraction by Packed Sorbent (MEPS) and LC-DAD-MS/MS.

The argan tree (Argania spinosa) is an endemic species from south-western Morocco. Argan-based preparations have been widely used in Moroccan traditional medicine for their biological properties, as well as for several cosmetic purposes. Whereas kernel, pulp of fruit and trunk have been extensively studied for their nutritional and pharmacological effects, relatively little is known about argan tree leaves. The main purpose of the present study is to investigate and characterise the bioactive phenolic fractions in both crude and aqueous extracts derived from argan tree leaves. A qualitative profile of the antioxidant phenolic compounds in argan leaves was obtained by means of structural hypothesis based on UV spectra and mass spectrometric fragmentation patterns. Moreover, selected phenolics were quantified in argan leaves by using a fully validated method based on liquid chromatography coupled to diode array detection and tandem mass spectrometry (LC-DAD-MS/MS). All the extracts were purified by a fast and reliable microextraction by packed sorbent (MEPS) procedure, before analysing them by LC-MS/MS. Based on retention times, mass spectrometric fragmentation and UV spectra, 13 phenolic compounds were identified or tentatively elucidated from crude and aqueous extracts derived from Argania spinosa leaves, while seven compounds were quantified in both extracts. The obtained results could represent a first step towards a complete characterisation of the argan plant, its bioactive profiling and the valorisation of its by-products as a source of potentially beneficial bioactive molecules.

Multi‐stage tandem mass spectrometric analysis of novel β‐cyclodextrin‐substituted and novel bis‐pyridinium gemini surfactants designed as nanomedical drug delivery agents

This study aimed at evaluating the collision-induced dissociation tandem mass spectrometric (CID-MS/MS) fragmentation patterns of novel β-cyclodextrin-substituted- and bis-pyridinium gemini surfactants currently being explored as nanomaterial drug delivery agents. In the β-cyclodextrin-substituted gemini surfactants, a β-cyclodextrin ring is grafted onto an N,N-bis(dimethylalkyl)-α,ω-aminoalkane-diammonium moiety using variable succinyl linkers. In contrast, the bis-pyridinium gemini surfactants are based on a 1,1'-(1,1'-(ethane-1,2-diylbis(sulfanediyl))bis(alkane-2,1-diyl))dipyridinium template, defined by two symmetrical N-alkylpyridinium parts connected through a fixed ethane dithiol spacer. Detection of the precursor ion [M](2+) species of the synthesized compounds and the determination of mass accuracies were conducted using a QqTOF-MS instrument. A multi-stage tandem MS analysis of the detected [M](2+) species was conducted using the QqQ-LIT-MS instrument. Both instruments were equipped with an electrospray ionization (ESI) source. Abundant precursor ion [M](2+) species were detected for all compounds at sub-1 ppm mass accuracies. The β-cyclodextrin-substituted compounds, fragmented via two main pathways: Pathway 1: the loss of one head-tail region produces a [M-(N(Me)2-R)](2+) ion, from which sugar moieties (Glc) are sequentially cleaved; Pathway 2: both head-tail regions are lost to give [M-2(N(Me)2-R)](+), followed by consecutive loss of Glc units. Alternatively, the cleavage of the Glc units could also have occurred simultaneously. Nevertheless, the fragmentation evolved around the quaternary ammonium cations, with characteristic cleavage of Glc moieties. For the bis-pyridinium gemini compounds, they either lost neutral pyridine(s) to give doubly charged ions (Pathway A) or formed complementary pyridinium alongside other singly charged ions (Pathway B). Similar to β-cyclodextrin-substituted compounds, the fragmentation was centered on the pyridinium functional groups. The MS(n) analyses of these novel gemini surfactants, reported here for the first time, revealed diagnostic ions for each compound, with a universal fragmentation pattern for each compound series. The diagnostic ions will be employed within liquid chromatography (LC)/MS/MS methods for screening, identification, and quantification of these compounds within biological samples.

Structure elucidation of chlorophyll catabolites (phyllobilins) by ESI-mass spectrometry—Pseudo-molecular ions and fragmentation analysis of a nonfluorescent chlorophyll catabolite (NCC)

The hyphenation of high performance chromatography with modern mass spectrometric techniques providing high-resolution data as well as structural information from MS/MS experiments has become a versatile tool for rapid natural product identification and characterization. A recent application of this methodology concerned the investigation of the annually occurring degradation of green plant pigments. Since the first structural elucidation of a breakdown product in the early 1990s, a number of similarly structured, tetrapyrrolic catabolites have been discovered with the help of chromatographic, spectroscopic and spectrometric methods. A prerequisite for a satisfactory, manually operated or database supported analysis of mass spectrometric fragmentation patterns is a deeper knowledge of the underlying gas phase chemistry. Still, a thorough investigation of the common fragmentation behavior of these ubiquitous, naturally occurring chlorophyll breakdown products is lacking. This study closes the gap and gives a comprehensive overview of collision-induced fragmentation reactions of a tetrapyrrolic nonfluorescent chlorophyll catabolite, which is intended to serve as a model compound for the substance class of phyllobilins.