Electrospray Ionization Time-of-flight Mass Spectrometry Research Articles

Dereplication of known nucleobase and nucleoside compounds in natural product extracts by capillary electrophoresis-high resolution mass spectrometry.

Nucleobase and nucleoside compounds exist widely in various organisms. An often occurring problem in the discovery of new bioactive compounds from natural products is reisolation of known nucleobase and nucleoside compounds. To resolve this problem, a capillary electrophoresis-high resolution mass spectrometry (CE-HR-MS) method providing both rapid separation and accurate mass full-scan MS data was developed for the first time to screen and dereplicate known nucleobase and nucleoside compounds in crude extracts of natural products. Instrumental parameters were optimized to obtain optimum conditions for CE separation and electrospray ionization-time-of-flight mass spectrometry (ESI-TOF/MS) detection. The proposed method was verified to be precise, reproducible, and sensitive. Using this method, known nucleobase and nucleoside compounds in different marine medicinal organisms including Syngnathus acus Linnaeus; Hippocampus japonicus Kaup and Anthopleura lanthogrammica Berkly were successfully observed and identified. This work demonstrates that CE-HR-MS combined with an accurate mass database may be used as a powerful tool for dereplicating known nucleobase and nucleoside compounds in different types of natural products. Rapid dereplication of known nucleobase and nucleoside compounds allows researchers to focus on other leads with greater potential to yield new substances.

Genotoxicological Assessment of Nebuloside-A a Triterpenoid Saponin Compound on Whole Blood DNA

We investigated the genotoxic effect of nebuloside-A on whole blood DNA by using alkaline Single Cell Gel Electrophoresis Comet assay. Saponins are a widespread class of bioactive compounds produced by many plant species. Nebuloside A was isolated from baby’s-breath (Gypsophila arrostii) by high performance liquid chromatography method. Mass spectra obtained by electrospray ionization-time of flight-mass spectrometry in a negative ion mode to reduce the protonation. Complete nuclear magnetic resonance spectroscopy assignments of nebuloside A was achieved by using 2D-nuclear magnetic resonance spectroscopy techniques, such as double-quantum filtered correlation spectroscopy, heteronuclear single quanthum correlation, heteronuclear multiple-bond correlation, and total correlation spectroscopy. DNA damage was measured in total arbitrary units by visual scoring of comets in different concentrations of nebuloside A and H2O2 treatments. We found that significant dose dependent relationship between nebuloside A and its genotoxic effect.

Screening and identification of multiple components in Tanreqing injection using RP-HPLC combined with DAD and ESI-TOF/MS

A liquid chromatography coupled with diode array detector (DAD) and electrospray ionization time-of-flight mass spectrometry (ESI-TOF/MS) method was developed for the screening and identification of the multiple components in Tanreqing injection, a well-known Chinese medicine injection in China. By combining the DAD spectrum and the accurate mass measurement of ESI-TOF/MS, twelve components in Tanreqing injection were identified. This study contributes to clarifying the nature of Tanreqing injection, and provides an effective and reliable process for the comprehensive and systematic characterization of complex traditional Chinese medicine preparations

Contribution of phenolics and essential oils to the antioxidant and antimicrobial properties of Disporopsis pernyi (Hua) Diels.

This study describes the characterization of essential oil and phenolic compounds in Disporopsis pernyi (Hua) Diels. The essential oil was analyzed by gas chromatography-mass spectroscopy (GC-MS) and twelve volatile bioactive compounds of D. pernyi were identified. Polyphenols were identified by reverse-phase high-performance liquid chromatography (RP-HPLC) coupled to electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) and quantified by ultrahigh-performance liquid chromatography (UPLC). A total of 4 polyphenolic compounds found in extract were identified as rutin, luteolin, quercetin, and betulinic acid. All obtained extracts and the 4 polyphenolic compounds were evaluated for their antimicrobial and antioxidant properties. The results suggested that the phenolic compounds contributed significantly to the antioxidant and antimicrobial activities of the plant.

Preparation and Characterization of Novel Polytitanium Tetrachloride Coagulant for Water Purification

Polymeric metal coagulants are increasingly being used to improve coagulation efficiency, yet the research on the development of titanium and particularly polytitanium salts remains limited. This study is the first attempt in the synthesis, characterization, and application of polytitanium salts as coagulants. Polytitanium tetrachloride (PTC) solutions with different basicity values B (OH/Ti molar ratio) were prepared using a slow alkaline titration method. Jar tests were conducted to assess coagulation performance using both synthetic and real raw water samples, and the floc characteristics were monitored online using a laser diffraction particle size analyzer. Electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) was utilized to identify various Ti species, with the results providing strong evidence of the presence of various hydrolyzed Ti species in the titanium aqueous phase. Compared to titanium tetrachloride (TiCl4), higher or comparable turbidity and organic matter removal efficiency could be achieved by PTC with improved floc characteristics in terms of size, growth rate, and structure. Besides, the water pH after PTC coagulation was significantly improved toward neutral pH. This study indicates that PTC is an effective and promising coagulant for water purification. Besides, the PTC flocculated sludge was able to recycle and produce functional TiO2 photocatalyst.

The highly modified microcin peptide plantazolicin is associated with nematicidal activity of Bacillus amyloliquefaciens FZB42

Bacillus amyloliquefaciens FZB42 has been shown to stimulate plant growth and to suppress the growth of plant pathogenic organisms including nematodes. However, the mechanism underlying its effect against nematodes remains unknown. In this study, we screened a random mutant library of B. amyloliquefaciens FZB42 generated by the mariner transposon TnYLB-1 and identified a mutant strain F5 with attenuated nematicidal activity. Reversible polymerase chain reaction revealed that three candidate genes RAMB_007470, yhdY, and prkA that were disrupted by the transposon in strain F5 potentially contributed to its decreased nematicidal activity. Bioassay of mutants impaired in the three candidate genes demonstrated that directed deletion of gene RBAM_007470 resulted in loss of nematicidal activity comparable with that of the F5 triple mutant. RBAM_007470 has been reported as being involved in biosynthesis of plantazolicin, a thiazole/oxazole-modified microcin with hitherto unknown function. Electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) analyses of surface extracts revealed that plantazolicin bearing a molecular weight of 1,354 Da was present in wild-type B. amyloliquefaciens FZB42, but absent in the ΔRABM_007470 mutant. Furthermore, bioassay of the organic extract containing plantazolicin also showed a moderate nematicidal activity. We conclude that a novel gene RBAM_007470 and its related metabolite are involved in the antagonistic effect exerted by B. amyloliquefaciens FZB42 against nematodes.

Characterisation of Phenolic Compounds by HPLC–TOF/IT/MS in Buds and Open Flowers of ‘Chemlali’ Olive Cultivar

Plant phenolics are secondary metabolites that constitute one of the most widely occurring groups of phytochemicals that play several important functions in plants. In olive (Olea europaea L), there is not enough information about the occurrence of these compounds in buds and flowers. To conduct a comprehensive characterisation of buds and open flowers from the olive cultivar 'Chemlali'. The polar fraction of buds and open flowers was extracted using solid-liquid extraction with hydro-alcoholic solvent. Then extracts were analysed using high performance liquid chromatography (HPLC) coupled to electrospray ionisation time-of-flight mass spectrometry (ESI/TOF/MS) and electrospray ionisation ion-trap tandem mass spectrometry (ESI/IT/MS²) operating in negative ion mode. Phenolic compounds from different classes including secoiridoids, flavonoids, simple phenols, cinnamic acid derivatives and lignans were tentatively identified in both extracts. Qualitatively, no significant difference was observed between flower buds and open flowers extracts. However, quantitatively the secoiridoids presented higher percentage of total phenols in open flowers (41.7%) than in flower buds (30.5%) in contrast to flavonoids, which decreased slightly from 38.1 to 26.7%. Cinnamic acid derivatives and simple phenols did not show any change. Lignans presented the lowest percentage in both extracts with an increase during the development of the flower bud to open flower. The HPLC-TOF/IT/MS allowed the characterisation, for the first time, of the phenolic profile of extracts of 'Chemlali' olive buds and open flowers, proving to be a very useful technique for the characterisation and structure elucidation of phenolic compounds.

Construction of Supramolecular Pyrene-Modified Metallacycles via Coordination-Driven Self-Assembly and Their Spectroscopic Behavior

The design and self-assembly of novel multipyrene hexagonal metallacycles via coordination-driven self-assembly is described. By employing newly designed 120° dipyridine donor and di-Pt(II) acceptor linkers substituted with pyrene, a variety of tris- and hexakis(pyrene) hexagonal metallacycles with well-defined shape and size were prepared via [3 + 3] and [6 + 6] self-assembly, respectively, under mild conditions in high yields. The structures of these novel metallacycles were well characterized by multinuclear NMR (31P and 1H) spectroscopy, cold-spray ionization time-of-flight mass spectrometry (CSI-TOF-MS), electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), and elemental analysis. The shape and size of all hexagonal metallacycles were investigated by the PM6 semiempirical molecular orbital method. The preliminary study of their spectroscopic behavior was also carried out. It was found that these pyrene-modified metallacycles displayed different optical behaviors, which might be cause...

Profiling of soluble neutral oligosaccharides from treated biomass using solid phase extraction and LC–TOF MS

Thermochemical pretreatments of cellulosic biomass are known to improve cell wall enzymatic digestibility, while simultaneously releasing substantial amounts of soluble oligosaccharides. Profiling of oligosaccharides released during pretreatment yields information essential for choosing glycosyl hydrolases necessary for cost-effective conversion of cellulosic biomass to desired biofuel/biochemical end-products. In this report we present a methodology for profiling of soluble neutral oligosaccharides released from ammonia fiber expansion (AFEX™)-pretreated corn stover. Our methodology employs solid phase extraction (SPE) enrichment of oligosaccharides using porous graphitized carbon (PGC), followed by high performance liquid chromatography (HPLC) separation using a polymeric amine based column and electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). For structural elucidation on the chromatographic time scale, nonselective multiplexed collision-induced dissociation was performed for quasi-simultaneous acquisition of oligosaccharide molecular and fragment masses in a single analysis. These analyses revealed glucans up to degree of polymerization (DP) 22 without modifications. Additionally, arabinoxylans up to DP=6 were detected in pretreated biomass extracts (post-enzymatic digestion). Cross-ring fragment ion abundances were consistent with assignment of linkages between sugar units in glucans and also xylose backbone in arabinoxylans as 1–4 linkages. Comprehensive profiling of soluble oligosaccharides also demonstrated decreases in levels of acetate esters of arabinoxylan oligosaccharides with concomitant increases in nonacetylated oligosaccharides that were consistent with earlier observations of 85% release of acetate esters by AFEX™ pretreatment.

Synthesis of selenolate-protected Au18(SeC6H5)14 nanoclusters

This work reports the first synthesis of selenophenolate-protected Au(18)(SePh)(14) nanoclusters. This cluster exhibits distinct differences from its thiolate analogue in terms of optical absorption properties. The Au(18)(SePh)(14) nanoclusters were obtained via a controlled reaction of Au(25)(SCH(2)CH(2)Ph)(18) with selenophenol. Electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) revealed the crude product to contain predominantly Au(18)(SePh)(14) nanoclusters, and side products include Au(15)(SePh)(13), Au(19)(SePh)(15) and Au(20)(SePh)(16). High-performance liquid chromatography (HPLC) was employed to isolate Au(18)(SePh)(14) nanoclusters. The results of thermogravimetric analysis (TGA), elemental analysis (EA), and (1)H/(13)C NMR spectroscopy confirmed the cluster composition. To the best of our knowledge, this is the first report of selenolate-protected Au(18) nanoclusters. Future theoretical and X-ray crystallographic work will reveal the geometric structure and the nature of selenolate-gold bonding in the nanocluster.

Identification and typing of Francisella tularensis with a highly automated genotyping assay

A PCR assay was developed to genotypically characterize Francisella tularensis and F. novicida. An integrated and partially redundant set of markers was selected to provide positive identification of these species, identify subspecies of F. tularensis and genotype 14 variable number tandem repeat (VNTR) markers. Assay performance was evaluated with 117 Francisella samples. Sample DNA was amplified, and the masses of the PCR products were determined with electrospray ionization/time of flight mass spectrometry (ESI-MS). The base compositions of the PCR amplicons were derived from these high-accuracy mass measurements and contrasted with databased information associated with each of the 25 assay markers. Species and subspecies determinations for all samples were fully concordant with results from established typing methods, and VNTR markers provided additional discrimination among samples. Sequence variants were observed with a number of assay markers, but these did not interfere with sample characterization, and served to increase the genetic diversity detected by the assay.

Photocatalytic decomposition of pharmaceutical ibuprofen pollutions in water over titania catalyst

Due to the growing importance of low concentrated pollution of surface, ground and drinking, the photocatalytic decomposition of ibuprofen down to low ppm concentrations over titania catalyst has been investigated in detail. The catalyst was characterized by XRD, TEM, diffuse reflection UV–Vis and nitrogen adsorption measurement. The photocatalytic abatement of ibuprofen was monitored by UV–Vis spectrometry, chromatographic by GC/MS, and HPLC coupled electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS). Catalytic performance has been studied by varying the catalyst and substrate concentration as well as decreasing the catalyst-to-substrate mass ratio over a wide range. The photocatalytic treatment with titania catalyst leads to rapid mineralization of ibuprofen. Formation of intermediate reaction products has been investigated. It is proposed that intermediates in part form oligomeric species, which are responsible for catalyst poisoning. Additional, the influence of the pH value, oxygen supply and catalyst re-use have been checked.

Application of nanoLC-ESI-TOF-MS for the metabolomic analysis of phenolic compounds from extra-virgin olive oil in treated colon-cancer cells

Crude phenolic extracts (PE) have been obtained from naturally bearing Spanish extra-virgin olive oil (EVOO) showing different polyphenol families such as secoiridoids, phenolic alcohols, lignans, and flavones. EVOO-derived complex phenols (especially from the Arbequina variety olive) have been shown to suppress cell growth of SW480 and HT29 human colon adenocarcinoma cell lines. Inhibition of proliferation by EVOO-PE Arbequina variety extract was accompanied by apoptosis in both colon-cancer-cell lines and a limited G₂M cell-cycle arrest in the case of SW480 cells. The metabolized compounds from EVOO-PE in culture medium and cytoplasm of both cell lines were analyzed using nano-liquid chromatography (nanoLC) coupled with electrospray ionization-time-of-flight-mass spectrometry (ESI-TOF-MS). The results showed many phenolic compounds and their metabolites both in the culture medium as well as in the cytoplasm. The main compounds identified from EVOO-PE were hydroxylated luteolin and decarboxymethyl oleuropein aglycone.

Electrochemical oxidation and protein adduct formation of aniline: a liquid chromatography/mass spectrometry study

Historically, skin sensitization tests are typically based on in vivo animal tests. However, for substances used in cosmetic products, these tests have to be replaced according to the European Commission regulation no. 1223/2009. Modification of skin proteins by electrophilic chemicals is a key process associated with the induction of skin sensitization. The present study investigates the capabilities of a purely instrumental setup to determine the potential of commonly used non-electrophilic chemicals to cause skin sensitization by the generation of electrophilic species from the parent compound. In this work, the electrophiles were generated by the electrochemical oxidation of aniline, a basic industrial chemical which may also be released from azo dyes in cosmetics. The compound is a known sensitizer and was oxidized in an electrochemical thin-layer cell which was coupled online to electrospray ionization-mass spectrometry. The electrochemical oxidation was performed on a boron-doped diamond working electrode, which is able to generate hydroxyl radicals in aqueous solutions at high potentials. Without any pretreatment, the oxidation products were identified by electrospray ionization/time-of-flight mass spectrometry (ESI-ToF-MS) using their exact masses. A mass voltammogram was generated by plotting the obtained mass spectra against the applied potential. Oligomerization states with up to six monomeric units in different redox states of aniline were observed using this setup. This approach was extended to generate adducts between the oxidation products of aniline and the tripeptide glutathione. Two adducts were identified with this trapping experiment. Protein modification was carried out subsequently: Aniline was oxidized at a constant potential and was allowed to react with β-lactoglobulin A (β-LGA) or human serum albumin (HSA), respectively. The generated adducts were analyzed by liquid chromatography coupled to ESI-ToF-MS. For both β-LGA and HSA, aniline adducts were successfully generated and identified.

Quality assessment and origin tracing of Guangdong Liangcha granules using direct mass spectrometry fingerprinting

A novel fingerprinting approach for quality assessment and origin tracing of Guangdong Liangcha granules (GLG) by electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) has been established. A negative-ion ESI-TOF spectrum gave the best chemical information and was most suitable to construct the chemical profile fingerprinting of GLG. Using high-resolution TOF-MS, 61 common mass spectral peaks based on the major constituents present in GLG were accurately and simultaneously detected without any chromatographic separation, providing valuable information for overall assessment of the quality and differentiation of the origin of the preparation. Six sources of commercial GLG products produced by five different manufacturers have been successfully differentiated, according to the principal component analysis of 61 common mass spectral peaks, and the stability of them was also assessed. The results of our experimental data demonstrated that ESI-TOF-MS fingerprinting is a useful tool for rapid pharmaceutical analysis, with promising prospects for overall quality assessment and origin differentiation of commercial pharmaceutical products.

Overlapping elution–extrusion counter-current chromatography: A novel method for efficient purification of natural cytotoxic andrographolides from Andrographis paniculata

Counter-current chromatography (CCC) is extremely useful for the separation, purification, and isolation of natural products. Recently, Berthod et al. [4,5] established an elution–extrusion CCC method in metabolic analysis by combining regular chromatographic elution with stationary-phase extrusion, which extends the hydrophobicity window of a counter-current separation. In this study, a novel overlapping elution–extrusion CCC method was developed and applied to the preparation of natural cytotoxic andrographolides from the aerial parts of Andrographis paniculata, a well-known Traditional Chinese Medicine (TCM) with potent anti-inflammatory effect and anti-cancer activity. Its theory was first developed, and then a series of CCC experiments were performed to investigate the efficiency of the method in the separation of the ethanol extracts from A. paniculata. Results show that overlapping elution–extrusion CCC is an efficient method to prepare a cytotoxic natural diterpenoid combination of 14-deoxy-andrographolide and 14-deoxy-11,12-didehydroandrographolide with the molar ratio of 1:2 as well as andrographolide using an optimized solvent system composed of hexane–ethyl acetate–ethanol–water (5:5:4:6, v/v) with an on-demand solvent preparation mode. All components obtained showed potent cytotoxic activity against human hepatocellular liver carcinoma cells HepG2 and doxorubicin-resistant R-HepG2 cells. Molecular structures have been identified by electrospray ionization mass spectrometry (ESI-MS), electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), one- and two-dimensional nuclear magnetic resonance (1D- and 2D-NMR). The method appears to be very useful for the high-throughput purification of natural products.

Quantification analysis of polymeric Al species in solutions with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS)

With the help of Ferron colorimetric method and 27Al NMR spectroscopy, quantification analysis method of electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) on Al speciation was developed and thus Al species in polymeric Al solutions were quantitatively analyzed. Based on the speciation results of mononuclear Al solution and purified Al 13 solution, Al species obtained with ESI-TOF-MS in polymeric Al solutions were classified into three categories as low polymers (i.e., Al 1–Al 10), mid polymers (i.e., Al 13–Al 20), and high polymers (i.e., Al 21–Al 31). Among these polymers, only a certain number of Al species have relative high content and constitute the dominant component of polymeric Al solutions. The quantification analysis results of ESI-TOF-MS agree well with those obtained by the other two traditional methods, which proves the feasibility of the novel method on Al species analysis. Additionally, ESI-TOF-MS can provide more information on Al speciation than 27Al NMR spectroscopy and Ferron colorimetric method, and the quantification analysis results can clearly explain the difference between the two traditional methods.

Simultaneous determination nucleosides in marine organisms using ultrasound‐assisted extraction followed by hydrophilic interaction liquid chromatography–electrospray ionization time‐of‐flight mass spectrometry

A new method has been developed based on ultrasound-assisted extraction (UAE) followed by hydrophilic interaction chromatography (HILIC) and electrospray ionization time-of-flight mass spectrometry (ESI-TOF/MS) for the simultaneous determination of 16 nucleosides and nucleobases in medicinal extracts of various marine organisms. The separation was achieved on a Venusil HILIC column (250×4.6 mm id, 5 μm) and gradient elution using a solution of acetonitrile and buffer (0.20% formic acid and 20 mmol/L ammonium acetate) as the mobile phase. Identification of the 16 target nucleosides and nucleobases was based on the retention time, UV spectra, and mass measurements of the protonated molecules ([M+H](+)) and main fragment ions (ESI-TOF/MS). In addition, non-target compounds of 2'-deoxyinosine and four other amino acids were also tentatively identified by ESI-TOF/MS. The 16 target compounds were quantified by HILIC-ESI-TOF/MS under optimized mass conditions. All calibration curves showed good linearity (r(2)>0.9951). The recoveries were 84.72-124.10%, and the limits of detection of the 16 target compounds were 0.6-130.0 ng/mL. The developed method was applied to quantify the target compounds in 15 batches of various marine organisms. The method has potential applicability for the identification and determination of highly polar and low-concentration active compounds in marine organisms.

Analysis of the extracts of Isatis tinctoria by new analytical approaches of HPLC, MS and NMR.

The methods of extraction, separation and analysis of alkaloids and indole glucosinolates (GLs) ofIsatis tinctoria were reviewed. Different analytical approaches such as High-pressure Liquid Chromatography (HPLC), Liquid Chromatography with Electrospray Ionization Mass Spectrometry (LC/ESI/MS), Electrospray Ionization Time-Of-Flight Mass Spectrometry (ESI-TOF-MS), and Nuclear Magnetic Resonance (NMR) were used to validate and identity of these constituents. These methods provide rapid separation, identification and quantitative measurements of alkaloids and GLs of Isatis tinctoria. By connection with different detectors to HPLC such as PDA, ELSD, ESI- and APCI-MS in positive and negative ion modes, complicated compounds could be detected with at least two independent detection modes. The molecular formula can be derived in a second step of ESI-TOF-MS data. But for some constituents, UV and MS cannot provide sufficient structure identification. After peak purification, NMR by semi-preparative HPLC can be used as a complementary method.

Analysis of oligonucleotides by hydrophilic interaction liquid chromatography coupled to negative ion electrospray ionization mass spectrometry

Hydrophilic interaction liquid chromatography (HILIC) is here successfully coupled to negative-ion electrospray ionization time-of-flight mass spectrometry (ESI-TOFMS) for the analysis of synthetic and chemically modified oligonucleotides. Separation was performed on a 2.1 mm × 100 mm PEEK ZIC ® HILIC column packed with hydrophilic stationary phase with a permanent zwitterionic functional group and a particle size of 3.5 μm with an average pore diameter of 200 Å. A method was developed to separate homogeneous and heterogeneous oligonucleotides as well as methylated oligonucleotides using a quaternary pumping system containing ammonium acetate and water with an acetonitrile gradient. Analyses of oligonucleotides were performed by LC/MS with a detection limit of 2.5 picomole (20 mer) with signal to noise ratio (S/N) of 4.12. The influence of the eluent composition, type of buffer and its concentration, and organic modifier were also evaluated. The HILIC LC/MS method presented in this paper used common, ‘MS friendly’, mobile phases achieving sensitive and selective oligonucleotide analysis.