ESI-MS Results Research Articles

Structure elucidation of active compounds from Coffea canephora Pierre ex A.Froehner cascara and their potential as anticancer against breast cancer cells

Context: One approach to cancer therapy medication is exploring medicinal plants that contain one or more compounds specifically targeting cancer cells with fewer side effects. Cascara from coffee fruit (Coffea canephora Pierre ex A.Froehner) is a waste rarely processed but has various chemical contents that can be used in medicine. Aims: To evaluate the in silico and in vitro activity of compounds isolated from ethanolic extract of C. canephora cascara against HeLa and MCF-7 breast cancer cells. Methods: Isolation of the compounds by radial chromatography and thin layer chromatography techniques, and the chemical structures were elucidated by infrared radiation, ultraviolet, nuclear magnetic resonance spectroscopy, and mass spectrometry. In silico study about the compounds binding with the receptor responsibility to cancer (caspases 3 and 9). In vitro study by examining the cytotoxicity of HeLa and MCF-7 cells of the isolated compounds from C. canephora. Results: Four known bioactive compounds, lupeol (1), stigmasterol (2), ursolic acid (3), and caffeic acid (4), were isolated from the ethanol extract of C. canephora cascara. Based on the ESI-MS results, the m/z value for lupeol was 427.50 [M+H]+, stigmasterol was 454.48 [M+ACN+H]+, ursolic acid was 456.51 [M+H]+, and caffeic acid was 179 [M-H]. In silico and in vitro data show that the ursolic acid compound has activity against HeLa and MCF-7 cancer cells with IC50 values of 25.98 ± 0.01 µg/mL and 12.70 ± 0.11 µg/mL, respectively. Conclusions: All isolated compounds from C. canephora cascara have a promising ability to interact with caspases 3 and 9, particularly ursolic acid, which has the smallest IC50 value against HeLa and MCF-7 breast cancer cells.

Water soluble Cu(II) and Zn(II) complexes of bidentate-morpholine based ligand: synthesis, spectral, DFT calculation, biological activities and molecular docking studies

Copper(II) and zinc(II) complexes of the type [ML(AcO)2.H2O] were synthesized from bidentate-morpholine based Schiff base ligand (L - morpholinopropylimino)methyl)-6-methoxyphenol). The prepared ligand, copper(II) and zinc(II) complexes were characterized by elemental analysis, ESI-MS, 1H-NMR, FT-IR, UV-Visible, ESR and spectrometric methods. The elemental and ESI-MS results have been established that the prepared ligand and complexes possess 1:1 stoichiometric ratio. 1H-NMR and FT-IR results have been suggested that azomethine nitrogen and morpholine ring nitrogen atoms are coordinated with Cu(II) and Zn(II) metal ions. UV-Visible, ESI-MS and ESR spectroscopic results have been supported that the proposed structure of Cu(II) and Zn(II) complexes possess square pyramidal geometry. In order to confirm the proposed square pyramidal geometry of prepared complexes by DFT calculation has been studied. DNA binding ability of Cu(II) and Zn(II) complexes have been studied by electronic absorption and viscometric methods. These results reveal that Cu(II) and Zn(II) complexes interact with CT-DNA by the way of groove binding mode. Molecular docking studies result shows that synthesized compounds has better binding ability. The in vitro antioxidant activities of ligand, Cu(II) and Zn(II) complexes have been investigated by using the DPPH assay. The result shows that synthesized compounds have good radical scavenging activity against DPPH radical. Antimicrobial activities of synthesized ligand and its complexes have been tested against selected bacterial (gram positive & gram negative) and fungal species. The results reveal that Cu(II) and Zn(II) have good antimicrobial activity than ligand. Communicated by Ramaswamy H. Sarma

A high selective fluorescent sensor for Cu2+ in solution and test paper strips

A novel and efficient fluorescent sensor with a pyrazine triphenylamine unit was developed. The sensor exhibits large Stokes shift (216 nm) due to the excited-state intramolecular proton transfer (ESIPT) process. After complexing with Cu2+, the ESIPT process was blocked and the fluorescence of the sensor was quenched. Job's plot and ESI-MS results indicated that the stoichiometric ratio between the sensor and Cu2+ was 1:1. The detection limit was determined to be 2.47 × 10−8 mol L−1. The sensor could be used to detect Cu2+ in practical samples with high accuracy. Furthermore, the sensor also could be made into test paper strips for the qualitative and quantitative detection of Cu2+.

Coupling Glucose Dehydrogenation with CO2 Hydrogenation by Hydrogen Transfer in Aqueous Media at Room Temperature.

Conversion of CO2 into value-added chemicals and fuels provides a direct solution to reduce excessive CO2 in the atmosphere. Herein, a novel catalytic reaction system is presented by coupling the dehydrogenation of glucose with the hydrogenation of a CO2 -derived salt, ammonium carbonate, in an ethanol-water mixture. For the first time, the hydrogenation of CO2 to formate by glucose has been achieved under ambient conditions. Under the optimal reaction conditions, the highest yield of formate reached approximately 46 %. We find that the apparent pH value in the ethanol-water mixture plays a central role in determining the performance of the hydrogen-transfer reaction. Based on the 13 C NMR and ESI-MS results, a possible pathway of the coupled glucose dehydrogenation and CO2 hydrogenation reactions was proposed.

An investigation of some Schiff base derivatives as chemosensors for Zn(II): The performance characteristics and potential applications

The fluorescence properties of four simple Schiff bases (LH2, LDMH2, LH2H and LDMHH2) and their potential application as chemosensors for the detection of zinc ion in aqueous solution have been investigated. While LH2 and LDMH2 have displayed specific recognition to Zn(II), the reduced derivatives (LH2H and LDMHH2) of these ligands have shown no fluorescence response due to the lack of CN group. The Job plots, fluorescence titration experiments and ESI-MS results indicate the formation of 1:1 complexes between sensors and Zn(II). The analytic methods based on LH2 and LDMH2 as chemosensors have been proposed and optimized to detect Zn(II) ions in aqueous solution. The optimized methods have shown a good range of linearity, high precision, good accuracy and low detection limit. As an alternative to these methods, LH2 and LDMH2 have the capability to detect Zn(II) ions by naked eye under UV lamp. Moreover, LH2-Zn and LDMH2-Zn complexes have the ability to be a staining agent for identifying the radiation treatment of food by DNA comet assay.

Copper-assisted interaction between amyloid-β and prion: Ternary metal complexes with Aβ N-terminus and octarepeat

Alzheimer and prion diseases are neurodegenerative disorders in which amyloid-beta (Aβ) and prion protein (PrP), respectively, failed their normal functions inducing cellular apoptosis. Histidine-based high-affinity metal-binding sites in the N-terminus domains, which favor the binding of transition metals such as copper and zinc, feature both Aβ and PrP. Recently, the biological role of copper(II) on the two protein interaction has been revealed. Many studies have been focused on copper(II) binding affinity for both Aβ or prion protein while ternary complexes formed by this metal with both proteins have not been investigated. Here we report a combined ESI MS, potentiometric and spectroscopic (CD, UV-Vis) study on ternary complexes formed by copper(II) ion with Aβ and PrP peptides fragments containing potential metal binding sites. In particular, Aβ(1-4), Aβ(1-6), Ac-Aβ(1-6), Aβ(1-16)PEG and the octarepeat (PHGGGWGQ) of prion protein were studied. ESI-MS results indicate that the formation of 1:1:1 ternary complexes occurred at the physiological pH range. Potentiometric and spectroscopic data demonstrate that in a large pH range, ternary species prevail over binary species with the histidine-driven amide deprotonation.

Characterization of catechin-α-lactalbumin conjugates and the improvement in β-carotene retention in an oil-in-water nanoemulsion

The goal of this study was to prepare and characterize α-lactalbumin (ALA)-catechin conjugates as a novel emulsifier in improving the retention of β-carotene (BC) in nanoemulsions via a free radical method. Covalent modification was observed and at least one catechin molecule was binding with ALA according to ESI–MS results. Far-UV CD indicated that the secondary structure of ALA was changed after conjugation. The Z-average particle diameters of nanoemulsions stabilized with ALA and ALA-catechin conjugates were 158.8 and 162.7nm, respectively. The increase of mean particle size and the degradation of BC at 50°C were both larger than at 25°C during 30days storage. BC retention stabilized with ALA-catechin conjugates was appreciably greater than ALA (control), which was attributed to the increase of ALA’s radicals-scavenging and free metal ion binding ability after grafting with catechin. The chemical antioxidant activities of ALA-catechin conjugates were increased with increasing concentrations from 0.1 to 1.0mg/ml. In general, labile phytochemicals, like BC, can be protected against oxidation during storage by proteins-polyphenols conjugates without any side effects.

Bioefficacy of Serratia marcescens isolated from entomopathogenic nematodes (EPN) and their secondary metabolite prodigiosin against Spodoptera litura

Bacterial strain SH1 was isolated from entomopathogenic nematodes (EPN) Heterorhabditis indica CP16 released from insect cavaders (Spodoptera litura). Their identification by API 20E Kit as well as by 16S rDNA sequencing showed that it belongs to the species Serratia marcescens. The isolate expressed the toxicity to Spodoptera litura. In the injection assay more than 65 % insects were killed after 10 h at 23 cfu/insect; in the ingestion assay (droplet on leaf surface), more than 50 % insects were killed after 72 h at 170 cfu/cm2. The red pigment produced by the isolate SH1 was confirmed to be one of its secondary metabolites – prodigiosin based on its color, UV/VIS spectra và ESI-MS results. When injected to Spodoptera litura at a dose of 422 ng/insect, the active compound killed approximately 65 % insects after 10 h of treatment, and in the ingestion assay (droplet on the leaf surface) at a dose of 27.66 ng/cm2 killed approximately 90 % insects after 120 h of treatment.

A highly selective sulfur-free iridium(iii)-complex-based phosphorescent chemidosimeter for detection of mercury(ii) ions

A neutral phosphorescent coordination compound bearing a benzimidazole ligand, Ir(pbi)(2)(acac) (Hpbi = 1,2-diphenyl-1H-benzo[d]imidazole; Hacac = acetylacetone), is demonstrated to be the first example of a sulfur-free iridium complex for the detection of Hg(2+) cations with high selectivity and sensitivity. Ir(pbi)(2)(acac) shows a multisignaling response towards mercury(II) ions through UV-vis absorption, phosphorescence and electrochemistry measurements. Upon addition of Hg(2+) ions, solutions of this complex change from yellow to colorless, which could be observed easily by the naked eye, while its phosphorescence turns from bright green (λ(PLmax) = 520 nm) into faint skyblue (λ(PLmax) = 476 nm), and the detection limit is calculated to be 2.4 × 10(-7) mol L(-1). (1)H NMR spectroscopic titration as well as ESI-MS results indicate that the decomposition of Ir(pbi)(2)(acac) in the presence of Hg(2+) through rupture of Ir-O bonds is responsible for the significant variations in both optical and electrochemical signals.

Metallacrowns of Ni(ii) with α-aminohydroxamic acids in aqueous solution: beyond a 12-MC-4, an unexpected (vacant?) 15-MC-5

Growing attention has been devoted in the recent years to a class of metallamacrocycles known as metallacrowns (MCs). They are structural analogues of crown ethers where the methylene bridges have been substituted by coordinative bonds formed by a transition metal ion ("ring" metal) and a nitrogen atom. The cavity of the metallacrown can accommodate an additional metal ion ("core" metal) either identical or different from the ring metal, thus forming a homo- or hetero-metallic MC. The most studied ring metal ion is certainly Cu(2+) and the aminohydroxamic acids have proved to be very suitable ligands to form MCs. The behavioural analogies between Cu(2+) and Ni(2+) in forming complexes, along with recent literature data in the solid state, prompted us to investigate the possible MC formation between Ni(2+) and both (S)-α-alaninehydroxamic acid and (S)-valinehydroxamic acid, in aqueous solution. Two metallacrowns, a 12-MC-4 and an unexpected 15-MC-5 have been detected by potentiometry and confirmed by ESI-MS results. Their structures are discussed on the basis of potentiometric, calorimetric, spectroscopic data and DFT calculations. The existence of a vacant 15-MC-5 species in solution can be put forward for the first time, making the present metal/ligand systems very interesting for their potential applications in cation recognition and separation. Finally, the crystal structure of the binary complex K[NiL(2)H(-1)]·5/3 H(2)O of (S)-α-alaninehydroxamic acid (LH) is also reported.

Reactivity of platinum-based antitumor drugs towards a Met- and His-rich 20mer peptide corresponding to the N-terminal domain of human copper transporter 1

Cellular uptake of platinum-based antitumor drugs is a critical step in the mechanism of the drug action and associated resistance, and deeper understanding of this step may inspire development of novel methods for new drugs with reduced resistance. Human copper transporter 1 (hCtr1), a copper influx protein, was recently found to facilitate the cellular entry of several platinum drugs. In the work reported here, we constructed a Met- and His-rich 20mer peptide (hCtr1-N20) corresponding to the N-terminal domain of hCtr1, which is the essential domain of hCtr1 for transporting platinum drugs. The interactions of the peptide with cisplatin and its analogues, including transplatin, carboplatin, oxaliplatin, and [Pt(L: -Met)Cl(2)], were explored at the molecular level. Electrospray ionization (ESI) mass spectrometry (MS) data revealed that all of the platinum(II) complexes used in present study can bind to hCtr1-N20 in 1:1 and 2:1 stoichiometry. Four Met residues should be involved in binding to cis-platinum complexes on the basis of the tandem MS spectrometry and previously reported data. Time-dependent 2D [(1)H,(15)N] heteronuclear single quantum coherence NMR spectra indicate the reaction of cisplatin with hCtr1-N20 is a stepwise process. The intermediate, however, is transient, which is consistent with the ESI-MS results. Time-dependent ESI-MS data revealed that the geometry and the properties of both the leaving and the nonleaving groups of platinum(II) complexes play essential roles in controlling the reactivity and formation of the final products with hCtr1-N20.

Effect of nonionic surfactants on the oxidation of carbaryl by anodic Fenton treatment

As a potentially promising technology, anodic Fenton treatment (AFT) has been shown to be very successful in pesticide removal. However, the influence of other constituents in the pesticide formulation, such as nonionic surfactants, has not been addressed. In this study, the effect of Triton X (TX) on the degradation kinetics and pathways of carbaryl undergoing AFT was investigated in an effort to facilitate its practical application. The presence of Triton X-100 was found to slow down the carbaryl degradation rate. This result can be attributed to the consumption of hydroxyl radicals ( OH) by surfactants and the formation of a carbaryl⋯TX⋯Fe 3+ complex, resulting in the unavailability of carbaryl to OH attack. The modified AFT kinetic model previously developed in this laboratory shows an excellent fit to the carbaryl degradation profile ( R 2>0.998), supporting the formation of a carbaryl⋯TX⋯Fe 3+ complex. The carbaryl degradation rate decreased as Triton X-100 concentration increased from 20 to 1000 mg L −1. Both OH consumption by surfactants and complex formation are responsible for the degradation rate reduction below the critical micelle concentration (CMC), whereas the complex and micelle formation becomes a more dominant factor above the CMC. The effect of ethylene oxide (EO) numbers of a given nonionic surfactant mainly lies in the consumption of hydroxyl radicals, which increases with the length of the EO chain, but does not significantly affect the formation of the carbaryl⋯TX⋯Fe 3+ complex. Based on the GC–MS and LC–ESI–MS results, no evidence was found that the carbaryl degradation pathway was affected. Carbaryl was typically oxidized to 1-naphthol and 1,4-naphthoquinone similar to what is observed in the absence of surfactants. Triton X-100 was degraded via the breakdown of EO chains and ω-oxidation of the terminal methyl group, which resulted in the production of a series of ethoxylate oligomers.

Chemical Modification of Insulin by N-phosphorylation

In this paper, the reactions of bovine insulin and small peptides, such as actin binding domain of thymosin β4 and Growth Hormone Releasing Factor (GRF 1–29 amino acids) with diisopropyloxyphosphite (DIPPH) and dimethyloxyphosphite (DMPH) were studied by modified Todd reaction. The MALDI-TOF or ESI-MS results showed that lysine, histidine and arginine residues in insulin could be phosphorylated under the water/ethanol system. The N,N,N-diisopropyloxyphosphorylated insulin analogues were characterized using MALDI-TOF and 31P NMR. These insulin analogues with different phosphorylation degree were separated and identified through LC-ESI-MS. In addition, circular dichroism (CD) spectra showed that the conformation of N,N,N-dimethyloxyphosphorylated insulin were only changed a little, whereas, that of N,N,N-diisopropyloxyphosphorylated insulin was changed completely.

Neutral glycolipids of the filamentous fungus Neurospora crassa:altered expression in plant defensin-resistant mutants

To defend themselves against fungal pathogens, plants produce numerous antifungal proteins and peptides, including defensins, some of which have been proposed to interact with fungal cell surface glycosphingolipid components. Although not known as a phytopathogen, the filamentous fungus Neurospora crassa possesses numerous genes similar to those required for plant pathogenesis identified in fungal pathogens (Galagan, J. E., et al. 2003. Nature 422: 859-868), and it has been used as a model for studying plant-phytopathogen interactions targeting fungal membrane components (Thevissen, K., et al. 2003. Peptides. 24: 1705-1712). For this study, neutral glycolipid components were extracted from wild-type and plant defensin-resistant mutant strains of N. crassa. The structures of purified components were elucidated by NMR spectroscopy and mass spectrometry. Neutral glycosphingolipids of both wild-type and mutant strains were characterized as beta-glucopyranosylceramides, but those of the mutants were found with structurally altered ceramides. Although the wild type expressed a preponderance of N-2'-hydroxy-(E)-Delta3-octadecenoate as the fatty-N-acyl component attached to the long-chain base (4E,8E)-9-methyl-4,8-sphingadienine, the mutant ceramides were found with mainly N-2'-hydroxyhexadecanoate instead. In addition, the mutant strains expressed highly increased levels of a sterol glucoside identified as ergosterol-beta-glucoside. The potential implications of these findings with respect to defensin resistance in the N. crassa mutants are discussed.

Electrospray mass spectrometry to study lake water DOM and effects of microbial degradation

Qualitative analysis of lake water dissolved organic matter (DOM) was carried out using electrospray ionization mass spectrometry (ESI MS) without prior clean-up or chromatography, showing the potential of ESI MS as a rapid method to analyse qualitative differences between DOM with different environmental properties. Spectra were evaluated in terms of the relative ion abundance in certain mass to charge ranges (m/z range), and the mass-to-charge average (m/z average). Lake water DOM from two different sources was used. In addition, DOM from both sources that had been subjected to microbial degradation under different oxygen regimes was analysed. ESI MS results were compared with those of UV absorbance and pollutant binding capacity (pyrene and atrazine). The results from all methods indicated qualitative differences between the DOM from different lakes, but only minor qualitative changes when comparing oxic and anoxic degradation. To detect those small differences the m/z range proved to be the more sensitive evaluation method, compared to the m/z average.

Quantitation of Lysergic Acid Diethylamide in Urine Using Atmospheric Pressure Matrix-Assisted Laser Desorption/Ionization Ion Trap Mass Spectrometry

A quantitative method was developed for analysis of lysergic acid diethylamide (LSD) in urine using atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry (AP MALDI-ITMS). Following solid-phase extraction of LSD from urine samples, extracts were analyzed by AP MALDI-ITMS. The identity of LSD was confirmed by fragmentation of the [M + H](+) ion using tandem mass spectrometry. The quantification of LSD was achieved using stable-isotope-labeled LSD (LSD-d(3)) as the internal standard. The [M + H](+) ion fragmented to produce a dominant fragment ion, which was used for a selected reaction monitoring (SRM) method for quantitative analysis of LSD. SRM was compared with selected ion monitoring and produced a wider linear range and lower limit of quantification. For SRM analysis of samples of LSD spiked in urine, the calibration curve was linear in the range of 1-100 ng/mL with a coefficient of determination, r(2), of 0.9917. This assay was used to determine LSD in urine samples and the AP MALDI-MS results were comparable to the HPLC/ ESI-MS results.

Nanosized Silver(I) Coordination Networks of Mixed Bix-Diphosphine (Bix = 1,4-Bis(imidazol-1-ylmethyl)benzene)

Assembly of silver(I) salts and bix in the presence of diphosphines provided four polymeric complexes [Ag(bix)(dppe)]n·nBF4 (1), [Ag(bix)(dppp)]n·nPF6 (2), [Ag(bix)(dppe)]n·nPF6·nCH3OH (3), and [Ag(bix)(dppe)]n·nSbF6·nCH3OH (4). X-ray diffraction analyses reveal that both 1 and 2 have a two-dimensional network composed of nanosized metallocyles, and the [Ag(bix)]n chains in 2 show alternate left and right helices. Complexes 3 and 4 are isomorphous, and they have 3D open frameworks of diamondoid topology with the size of 13 × 13 A2 along the b-axis. Possible formation processes were interpreted by ESI-MS results.

Gas Phase, Solution, and Solid State Alkali Ion Binding by the [NbE8]3‐ (E: As, Sb) Complexes: Synthesis, Structure, and Spectroscopy.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Gas phase, solution, and solid state alkali ion binding by the [NbE8](3-) (E = As, Sb) complexes: synthesis, structure, and spectroscopy.

Toluene solutions of Nb(toluene)(2) react with ethylenediamine solutions of K(3)E(7) (E = As, Sb) in the presence of 2,2,2-crypt to give [NbAs(8)](3-) (2) and [NbSb(8)](3-) (3) ions, respectively, in low yields. The (133)Cs NMR spectroscopy, ESIMS results (negative ion mode), and single-crystal X-ray structures of the ions are reported. The complexes have S(8)-like E(8) rings with Nb atoms in the center. The 1:1 complex of 2 with Cs+ was observed in solution and also in the gas phase as the oxidized ion [CsNbAs(8)](1-). The anion 2 selectively binds to Cs(+) in solution even in the presence of excess Na(+). Other gas-phase ions formed include [Cs(2)(NbAs(8))](1-), [KCs(NbAs(8))](1-), [KCs(NbAs(8))(2)](1-), [KNbAs(8)](1-), and [K(2)NbAs(8)](1-).

Interaction of desferrioxamine B (DFB) model dihydroxamic acids with some essential and toxic metal(II) ions: effects of the structure and length of connecting chains on the metal ion selectivity.

Complexation of desferrioxamine B (DFB) model dihydroxamic acids (HO(CH3)NCO(CH2)xCONH(CH2)yCON(CH3)OH where x = 2, 3, y = 5, 4, 3, 2, and the compounds are abbreviated as 2,5-DIHA, 2,4-DIHA, 2,3-DIHA, 2,2-DIHA, 3,4-DIHA and 3,3-DIHA, respectively) with Cu(II), Ni(II), Zn(II), Pb(II) and Cd(II) was studied by pH-potentiometric and spectroscopic (UV-VIS, NMR and ESI-MS) techniques. The effects of the position of the peptide group, the chain length and the geometry on the stability and stoichiometry of the complexes formed were evaluated. It was concluded that metal ions preferring regular octahedral geometry in their complexes form the most stable bis-chelated mononuclear complexes, [ML], with 2,5-DIHA having the same connecting chain structure and length as those of DFB. This benefit of 2,5-DIHA, however, almost disappears in the case of Cu(II). With this metal, which prefers the equatorial coordination of two hydroxamates, the parallel formation of both [CuL] and [Cu2L2] was found. ESI-MS results indicate that the latter complex is exclusively formed with 2,2-DIHA involving the shortest linker. All these dihydroxamic acids are excellent chelating agents for Pb(II). The special geometry determined by the lone pair electrons should be responsible for the somewhat unique preference order of the ligands towards the Pb(II) ion, for the favoured formation of the monomeric bis-chelated complexes and also for the unexpectedly high stability of the species [Pb(2,2-DIHA)].