ESI-MS Spectra Research Articles

A ratiometric turn-on chemosensor for highly selective and sensitive visual detection of Zn2+ and its applications to environmental samples

A new chemosensor (2-hydroxy-5-methyl-1,3-phenylene)bis(methaneylylidene)) dipicolinohydrazonamide (DP) has been successfully developed, which exhibits a specific selectivity by detecting Zn2+ ions in IPA/water solutions. The receptor DP demonstrates a rapid increase in fluorescence upon detection of Zn2+ without interference from other ions. A substantial fluorescence enhancement was noticed after the addition of Zn2+ ions. Receptor DP has excellent selectivity and sensitivity towards Zn2+ ions over the other metal ions in a semi-aqueous medium, with a low detection limit of 24 μM. In addition, the fluorescence sensing mechanism is further examined using the job’s plot and ESI-MS spectra. Moreover, the density functional theory (DFT) simulations are used to determine the optimal geometries of DP and its complexity, resulting in enhancing our comprehension of the sensing mechanism. Significantly, the non-toxic DP may effectively serve as a visual tool for accurately detecting the presence of Zn2+ in SBG cells, test strips, and water samples, which could have important implications for its possible use in biology and the environment.

A turn-off xanthene-based fluorescent probe for detection of cysteine and its practical application in bioimaging and food samples

BackgroundCys, as an essential amino acid that can be ingested from daily food, plays an important role in maintaining the oxidative balance in cells. Abnormal Cys levels in organisms will lead to various diseases. Therefore, it is of great significance to construct a fluorescent probe that can detect Cys levels in food and biological systems. ResultsHere, a turn-off type probe TA had been successfully synthesized, which attached diethylamine as the strong electron donor, acrylate as the weak electron donor, and xanthene as the π-bridge. TA showed wonderful selectivity, low detection limit, good photostability and well live-cell compatibility for Cys by reducing acrylate group to hydroxyl group of TAOH. The reaction mechanism was demonstrated by 1H NMR, ESI-MS spectra, pH-dependent response experiments, and DFT calculations. Importantly, the reason why TAOH exhibited no fluorescence was the disappearance of the ICT effect in the molecule due to the dominant existence of spirocyclic state of TAOH. In addition, the probe can be used not only for the imaging detection of Cys in A549 cells and zebrafish, but also for the detection of Cys levels in food samples. SignificanceThis work provides a new idea for the design of Cys fluorescent probe, which may be beneficial to the comprehension of the potential mechanism of novel fluorescent probe.

A mitochondrial targeted dual ratiometric near-infrared fluorescent probe based on ICT effect for the detection of SO2 derivative and its bioimaging

SO2 derivatives play an important role in many metabolic processes, excessive ingestion of them can lead to serious complications of various diseases. In this work, a novel dual ratiometric NIR fluorescent probe XT-CHO based on ICT effect was synthesized for detecting SO2 derivative. In the design of the probe, the α, β-unsaturated bond formed between benzopyran and coumarin was used as the reaction site for SO2, meanwhile, the extended π-conjugate system promoted maximum emission wavelength of the probe up to 708 nm. Notably, the probe exhibited high selectivity and sensitivity for detecting SO2, the limit of detection reached 2.13 nM and 58.5 nM in fluorescence spectra and UV–Vis absorption spectra, respectively. The reaction mechanism of SO2 and XT-CHO had been verified by 1H NMR, ESI-MS spectra and DFT calculation. Moreover, the probe was successfully applied in detecting endogenous and exogenous SO2 in living cells and proved possessed the mitochondrial targeted ability.

New Derivatives of 1-(3-Methyl-1-Benzofuran-2-yl)Ethan-1-one: Synthesis and Preliminary Studies of Biological Activity.

A set of nine derivatives, including five brominated compounds, was synthesized and the structures of these novel compounds were confirmed using 1H and 13C NMR as well as ESI MS spectra. These compounds were tested on four different cancer cell lines, chronic myelogenous leukemia (K562), prostate cancer (PC3), colon cancer (SW620), human kidney cancer (Caki 1), and on healthy human keratocytes (HaCaT). MTT results reveal that two newly developed derivatives (6 and 8) exhibit selective action towards K562 cells and no toxic effect in HaCat cells. The biological activity of these two most promising compounds was evaluated by trypan blue assay, reactive oxygen species generation, and IL-6 secretion. To investigate the proapoptotic activity of selected compounds, the two following types of tests were performed: Annexin V Apoptosis Detection Kit I and Caspase-Glo 3/7 assay. The studies of the mechanism showed that both compounds have pro-oxidative effects and increase reactive oxygen species in cancer cells, especially at 12 h incubation. Through the Caspase-Glo 3/7 assay, the proapoptotic properties of both compounds were confirmed. The Annexin V-FITC test revealed that compounds 6 and 8 induce apoptosis in K562 cells. Both compounds inhibit the release of proinflammatory interleukin 6 (IL-6) in K562 cells. Additionally, all compounds were screened for their antibacterial activities using standard and clinical strains. Within the studied group, compound 7 showed moderate activity towards Gram-positive strains in antimicrobial studies, with MIC values ranging from 16 to 64 µg/mL.

Tri-armed Schiff base fluorescent sensor for the rapid recognition of Zn(II): application in live cell imaging, test strips and TLC.

Various metal ions exist in nature and human beings and play limitless vital roles in both the atmosphere and biology. A fundamental and useful aspect is the qualitative and quantitative assessment of Zn(II) at concentration levels as low as parts per billion (ppb). Thus, the design and development of novel fluorescent turn-on receptors have gained significant interest because of their potential for use in live cell imaging to detect biologically relevant metal ions with high selectivity and sensitivity. The present research illustrates the design and synthesis of a novel fluorescent sensor [(1,3,5-triazine-2,4,6-triyl)tris(hydrazine-2-yl-1-ylidene)tris(methaneylylidene)]tris(2,4-di-tert-butylphenol) (THDBP) for the selective and sensitive probing of Zn(II). The sensor exhibited a fluorescence turn-on mechanism upon treatment with Zn(II) ions at λemi. 503 nm in aq. acetonitrile. The formation of a 1 : 3 complex between THDBP and Zn(II) is confirmed from the Job plot and ESI-MS spectrum. The evaluated limit of detection (LOD) and association constant (Ka) of the sensor THDBP for Zn(II) were found to be 1.03 × 10-10 M and 2.33 × 108 M-1, respectively. Further research demonstrates the practical application of the sensor for the detection of Zn(II) ions in live cells. The sensing ability of the sensor THDBP was also explored through inexpensive test strips and TLC sheets.

A highly sensitive triazole-based perfectly water soluble novel bis-Schiff base reversible fluorescent-colorimetric chemosensor for fast detection of Pb2+ ions.

A reversible fluorescent-colorimetric azino bis-Schiff base receptor for the detection of Pb2+ in aqueous medium has been developed for the first time. Receptor L exhibits an excellent selective and rapid fluorescent-colorimetric response towards Pb2+. The sensitivity of the fluorescent-based assay (0.53 nM) and colorimetric assay (1.0 nM) for Pb2+ is sufficiently good in comparison to previously reported literature. From 1H NMR data, Job plot measurement and the ESI-MS spectrum, a 1 : 2 stoichiometric complexation between L and Pb2+ has been established. Receptor L shows a remarkable detection ability in a wide pH range of 4-8 and it has been successfully utilised in the determination of Pb2+ in aqueous solution of bovine serum albumin protein and in real samples. The geometry of L has been optimized by both DFT studies and NMR, FTIR and mass spectra. Moreover, we have studied molecular docking of the probe L.

Dynamic Metallosupramolecular Cages Containing 12 Adaptable Pockets for High-Order Guest Binding Beyond Biomimicry.

Molecular recognition lies at the heart of biological functions, which inspires lasting research in artificial host syntheses to mimic biomolecules that can recognize, process, and transport molecules with the highest level of complexity; nonetheless, the design principle and quantifying methodology of artificial hosts for multiple guests (≥4) remain a formidable task. Herein, we report two rhombic dodecahedral cages [(Zn/Fe)8Pd6-MOC-16], which embrace 12 adaptive pockets for multiguest binding with distinct conformational dynamics inherent in metal-center lability and are able to capture 4-24 guests to manifest a surprising complexity of binding scenarios. The exceptional high-order and hierarchical encapsulation phenomena suggest a wide host-guest dynamic-fit, enabling conformational adjustment and adaptation beyond the duality of induced-fit and conformational selection in protein interactions. A critical inspection of the host-guest binding events in solution has been performed by NMR and ESI-MS spectra, highlighting the importance of acquiring a reliable binding repertoire from different techniques and the uncertainty of quantifying the binding affinities of multiplying guests by an oversimplified method.

Molecular recognition of carbonate ion using a novel turn-on fluorescent probe

A novel turn-on fluorescent probe 3 was synthesized by condensing salicylaldehyde and nicotinic hydrazide for the selective detection of CO32– in aqueous medium. Probe 3 exhibited a turn-on fluorescence response toward CO32– with excellent selectivity, sensitivity (DL = 2.76 μM), and good reversibility. The binding constant (K) of probe 3 with CO32– was calculated to be 5 × 103 M−1 (log K 3.69). The 1:1 stoichiometry of the complex between probe 3 and CO32– ions was confirmed by Job's plot and ESI-MS spectra. Deprotonation and hydrogen-bonding interactions are involved in the recognition of CO32– ion, which was also suggested by 1H NMR, ESI-MS spectra, and Density Functional Theory (DFT) calculations. Moreover, an INHIBIT type molecular logic gate was constructed by using 3:CO32– and CH3COOH as inputs and current signal as output. Owing to the practical applications, probe 3 demonstrated its efficiency in quantifying CO32– ion in real water samples through standard addition method, thus showcasing its potential in real environment. Further, the MTT assay indicated very low cytotoxicity (IC50 = 1 mM) of probe 3 and also the cell imaging experiments demonstrated the effective sensing of CO32– ions with probe 3 in the biological systems.

A combined theoretical and experimental study of ratiometric fluorescent Schiff base chemosensor for detection of Fe3+ ion and its anticancer activity

Schiff-base fluorescent chemosensor (E)-N-(4-(dimethylamino)benzylidene)quinolone-3-amine (DBQA) was synthesized and characterized by FT-IR,1H NMR,13C NMR, ESI-MS spectrometry and Single X-ray crystallographic studies. The synthesized chemosensor (DBQA) was used for the detection of Fe3+ successfully. UV-visible and fluorescence spectra of (DBQA) exhibits a ratiometric behaviour along with a bathochromic shift upon the successive addition of Fe3+. The fluorescence spectra of chemosensor (DBQA) were recorded followed by addition of concentrations of different metal ions and NH3. The chemosensor (DBQA) showed a favourable linear relationship between the fluorescence intensity and concentration of Fe3+ ion. DBQA exhibits a ratiometric response and illustrates high sensitivity (with a detection limit of 0.4 ​μM) and good selectivity for the Fe3+ ion over other transition metal ions. DBQA shows 0.6 ​μM detection limit for NH3 along with ratiometric behaviour also. The association constant (Ka) of chemosensor (DBQA) was found to be 1.455×102 ​M-1/2 for Fe3+. The mechanism of sensing of the present ratiometric fluorescent chemosensor (DBQA) was explained by ICT (Intra-molecular charge transfer) using DFT calculations. The interaction model of chemosensor (DBQA) with Fe3+ was determined to be 2:1 stoichiometry using Job's plot analysis and ESI-MS spectra which further confirms DFT studies. Moreover, tested DBQA ​+ ​Fe3+ was showed that remarkable anticancer activity against the HCT116 colon cancer cells by MTT assay. Novelty and importance of DBQA as it can be investigate, test or analyse of detect Fe3+ rapidly as compared to other tested ions. Lastly, DBQA can be investigate, test or analyse of Fe3+ in environmental and biological samples.

GABase and glutaminase inhibitory activities of herbal extracts and acylated flavonol monoglycosides isolated from the leaves of Laurus nobilis L.

This study was to compare GABase [a mixture of γ-aminobutyric acid (GABA) aminotransferase and succinic semialdehyde dehydrogenase] and glutaminase inhibitory activities of 20 herbal extracts and investigate the isolation, structural elucidation and those inhibitory activities of three acylated flavonol monoglycosides from the selected extract of Laurus nobilis L. (laurel). On the basis of the NMR spectroscopic data and the ESI MS spectra together with the comparison with the literature values, three compounds were identified as kaempferol-3-O-(4″-E-p-coumaroyl)-α-l-rhamnopyranoside (1), kaempferol-3-O-(3″,4″-di-E-p-coumaroyl)-α-l-rhamnopyranoside (2) and kaempferol-3-O-(2″,4″-di-E-p-coumaroyl)-α-l-rhamnopyranoside (3), respectively. The IC50 values of GABase inhibitory activity of 1-3 and p-hydroxybenzaldehyde (HBA) as control were 0.24 mM, 0.14 mM, 0.12 mM and 0.43 mM, respectively. Additionally, the IC50 values of glutaminase inhibitory activity of 1-3 and 6-diazo-5-oxo-l-norleucine (DON) as control were 0.34 mM, 0.13 mM, 0.14 mM and 0.33 mM, respectively. The results suggest that the extract from laurel shows the strongest biological activities among 20 herbal extracts and three acylated flavonol monoglycosides may serve as potential lead compounds for the prevention and treatment of neurodegenerative and lifestyle-related diseases by targeting GABase and glutaminase. This is the first report on GABase and glutaminase inhibitory activities of 1-3.

The highly selective and sensitive fluorescent detection of SO2 based on an emissive quinoline derivative probe

Sulfur dioxide (SO2) is a common global air pollutant that can cause serious air pollution and lead to a variety of severe diseases. In this study, a tripodal quinoline-based derivative T with two reversible conformations is synthesized. T demonstrates highly selective, sensitive fluorescent SO2 detection in solution. As SO2 is added into a dioxane/water solution, the sensor T purple emission rapidly changes to a green color in a strongly acidic environment. T showed high sensitivity and selectivity toward H2SO4 and SO2 detecting with good detection limits as low as 0.098 μM and 5.438 μM, respectively. The fluorescence sensing process is successfully confirmed via FT-IR, NMR, and ESI-Ms spectrum. Furthermore, DFT calculation reveals the potentially reversible conformation transfer mechanism and selective, sensitive fluorescence sensing behavior driven by host-guest and multiple hydrogen bonding interactions in solution.

Synthesis and Anticancer Activity of Novel Thiazolo-Coumarin Derivatives

As a starting point for creating new inhibitor scaffolds, a molecular hybridization approach was applied in designing the novel molecules using coumarin-thiazole hybrids as mPGES-1 enzyme inhibitors. Thus, in present work, the novel thiazolo coumarin derivatives (8-35) were synthesized and characterized by 1H NMR, IR and ESI-MS spectra. All the synthesized molecules (8-35) were also investigated for their anticancer activity on MCF-7 (breast cancer), caco-2 (colon cancer), HeLa (Cervix cancer) cell lines. Studies revealed that compounds (8-14) and (22-28) showed inhibition (IC50) at different concentrations of 12.5, 50, 100 μg/mL and more than 100 μg/mL.

Anti-peptic Ulcer of the N-hexane Fraction from Sanchezia nobilis Hook.F. Leaves and its Isolated Compounds

The n-hexane fraction of the Sanchezia nobilis Hook.f. leaves was evaluated for its effect on the gastric ulcer with pyloric ligation (Shay) rat model, analgesia effect on hot plate model and pain threshold meter, and inhibitory effect on Helicobacter pylori (H.P). The data showed a significant reduction in ulcer score, gastric volume, and total acidity and tended to reduce free acidity and increase gastric pH. In addition, the n-hexane fraction had a central analgesic effect and H.P inhibition. Chemical investigation of the n-hexane fraction resulted in the isolation of the four compounds (1 – 4). By using NMR and ESI-MS spectra, these compounds were identified chemical structures (3β, 5α, 22E)-stigmasta-7,22-dien-3-ol (1), coccinic acid (2), 7-hydroxy-6-methoxy coumarin (3), and betulinic acid (4). All compounds were reported for the first time from the Sanchezia genus.
 
 

Luminescent Pyrene-based Schiff base Receptor for Hazardous Mercury(II) Detection Demonstrated by Cell Imaging and Test Strip.

Qualitative and quantitative analysis of mercury at concentration levels as low as parts per billion (ppb) is a basic and practical concern. The vast majority of research in this field has centered on the development of potent chemosensor to monitor mercuric (Hg2+) ions. Mercury exists in three oxidation states, + 2, + 1 and 0, all of which are highly poisonous. In this study, (N1E,N2E)-N1,N2-bis(pyrene-1-ylmethylene)benzene-1,2-diamine (PAPM), a novel photoluminescent sensor based on pyrene platform was synthesized. Over the tested metal ions (Cd2+, Co2+, Cu2+, Mg2+, Mn2+, Ni2+, K+, Na+, Zn2+, Sr2+, Pb2+, Al3+, Cr3+ and Fe3+) the sensor responds only to Hg2+ by showing high selectivity and sensitivity. After treatment with mercuric ions at room temperature, the luminescence intensity of probe was quenched at 456nm. The quenching of fluorescence intensity of probe upon addition of mercury is due to the effect of "turn-off" chelation enhanced quenching (CHEQ) by the formation of 1:1 complex. The ESI-MS spectrum and the Job's experimental results confirm the formation of 1:1 complex between PAPM and Hg2+. The detection limit and association constant of sensor for mercury is computed using fluorescence titration data and were found to be 9.0 × 10-8M and 1.29 × 105M-1 respectively. The practical application of sensor towards recognition of mercury(II) ions was explored through economically viable test strips and also using cell imaging studies.

Noncytotoxic 16,23-epoxycucurbitacin-type triterpenoids from Elaeocarpus hainanensis

Phytochemical investigation of methanol extract from Elaeocarpus hainanensis Oliv. leaves and twigs led to the isolation and structural determination of three 16,23-epoxycucurbitacin-type triterpenoids, including a new hydroperoxide, 16α,23α-epoxy-3β,20β-dihydroxy-24α-hydroperoxy-10αH,23βH-cucurbit-5,25-dien-11-one (elahainencin A, 1), and two known analogs (2 and 3). Their chemical structures were determined by the spectroscopic analyses, including 1 D-, 2 D NMR and HR ESI MS spectra. Compound 1 represents a cucurbitacin derivative incorporating a hydroperoxide. In addition, these isolated compounds have been found to be noncytotoxic when tested in vitro against five human cancer cell lines (A549, T24, 8505, Huh-7 and SNU-1) by using the SRB method.

A New 7‐Azaindole Structure Analog: Molecular Docking, Synthesis and Preliminary Biological Activity in Vitro for Anticancer

In this work, a series of 7-azaindole analogs were designed by the bioisosteric principle based on the pharmacodynamic parent nucleus. Moreover, 5-[(5-chloro-1H-pyrrolo[2,3-b]pyridin-3-yl)methyl]-N-{[6-(trifluoromethyl)pyridin-3-yl]methyl}pyrimidin-2-amine (compound P1) with the strongest interaction with colony-stimulating factor 1 receptor (CSF-1R) was screened by molecular docking. Compound P1 was successfully prepared by the six-step reaction with HPLC purity of 99.26 % and characterized by 1 H-NMR and ESI-MS spectra. In vitro bioactivity study showed that compound P1 appeared the cytotoxicity to MCF-7 and A549 cells, especially to HOS cells (IC50 =88.79±8.07 nM), while it had lower toxicity to normal L929 cells (IC50 =140.49±8.03 μM). In addition, compound P1 could induce HOS cell death by apoptosis and blocking the G0/G1 phase at nanomolar concentrations. The obtained results indicated that compound P1 might be a promising candidate compound for anticancer drug.

Alliacane-Type Secondary Metabolites from Submerged Cultures of the Basidiomycete Clitocybe nebularis

Seven sesquiterpenoids, named nebucanes A-G (1-7), featuring a rare alliacane scaffold with unprecedented furan or pyrrole functions, were isolated from the fermentation broth of Clitocybe nebularis. Their structures were established on the basis of 1D/2D NMR spectroscopic analyses, HR-(+)-ESIMS spectra, and comparison of measured and calculated CD spectra for determination of the absolute configuration. Assessing the biological activities, nebucane D (4) exhibited antifungal effects against Rhodotorula glutinis, while nebucane G (7) displayed significant cytotoxicity against MCF-7 and A431 cell lines.

Synthesis of a novel nucleotide unit containing cytosine analog bearing phosphodiester function and formation of silver(I)-mediated DNA duplex

Novel modified cytosine analogs bearing phosphodiester/thiophosphodiester functionality were synthesized. The interactions between different metal ions and modified cytosine-cytosine base-pairs in DNA duplexes were investigated by UV-melting experiments. The thiophosphodiester modification binds to the Ag(I) ions strongly compared to the phosphodiester counterpart as examined in ESI-MS spectra as well.

In vitro and in silico cytotoxic activities of triterpenoids from the leaves of Aralia dasyphylla Miq. and the assessment of their ADMET properties

From the methanol extract of the leaves of Aralia dasyphylla Miq. (Araliaceae), ten triterpenoids including five ursane-type triterpenoids, ursolic acid (1), 3-O-α-l-arabinopyranosyl ursolic acid (2), ursolic acid 28-O-β-D-glucopyranosyl ester (3), 3-O-[β-D-glucopyranosyl (l→3)]-α-L-arabinopyranosyl ursolic acid (4), and matesaponin 1 (5), and five oleanane-type triterpenoids, elatoside E (6), elatoside F (7), 3-O-[β-D-glucopyranosyl (l→3)]-α-L-arabinopyranosyl oleanolic acid (8), 3-O-α-L-arabinopyranosyl oleanolic acid (9) and oleanolic acid 28-O-β-D-glucopyranosyl ester (10) were isolated. Their structures were elucidated based on 1D-, 2D-NMR and ESI-MS spectra as well as by comparison with those reported in the literature. All isolated compounds were evaluated in vitro for their cytotoxic activities against three human cancer cell lines (HepG2, LU-1 and RD) and in silico by molecular docking studies on human glucose transporter 1 (hGLUT1) protein. The triterpenoids 2, 4, 6, 8 and 9 exhibited good growth inhibition of HepG2 and LU-1 cancer cell lines with IC50 values in the range 1.76 − 7.21 (μM). The oleanane type triterpenoid 8 was the highest cytotoxic compound to inhibit all the tested cancer cell lines with IC50 values of 2.73 ± 0.12, 1.76 ± 0.11, 2.63 ± 0.10 μM, respectively. The in silico molecular docking study results showed that compounds 4 and 6 had the highest binding affinity. Compounds 1–10 were evaluated for their in silico ADMET of absorption, distribution, metabolism, excretion and oral toxicity parameters. Compounds 6, 8, 9 and 10 from A. dasyphylla are potential hGLUT1 inhibitors and worth of further investigation for the prevention or treatment of diabetes and cancer. Communicated by Ramaswamy H. Sarma

A highly selective and sensitive salamo-salen-salamo hybrid fluorometic chemosensor for identification of Zn2+ and the continuous recognition of phosphate anions

A salamo-salen-salamo hybrid fluorescent chemical sensor (H4L) was synthesized and characterized. It exhibits high selectivity and sensitivity to Zn2+ in physiological pH range. Meanwhile, its zinc(II) complex (L-Zn2+) continuously responses phosphate anions in DMF/H2O (v/v, 9:1) solution. Moreover, the identification processes are explored using characterization methods such as UV-absorption spectra, IR spectra and ESI-MS spectrum. In addition, the coordination mechanism of H2PO4− and Zn2+ were successfully exploited to make the chemical sensor reproducible. In short, the sensors H4L and L-Zn2+ will be promising detection devices for Zn2+ and phosphate anions.