HRMS Measurements Research Articles

Microwave-assisted regioselective [1,3]-dipolar cycloaddition of 3-methyl-2-(substitutedbenzylidene)-5-oxopyrazolidin-2-ium-1-ides to benzothiophene 1,1-dioxide

A series of pyrazolidinium ylides was reacted with benzothiophene 1,1-dioxide to afford (3R,5S,5aS,10bS)-3-methyl-5-substitutedphenyl-2,3,5,5a-tetrahydrobenzo[4,5]thieno[3,2-c]pyrazolo[1,2-a]pyrazol-1(10bH)-one 6,6-dioxides under microwave irradiation and their structures were identified by means of spectral/physical characteristics including X-ray diffraction data and HRMS measurements.

Easily accessible ferric ion chemosensor based on rhodamine derivative and its reversible OFF–ON fluorescence response

An easily accessible ferric ion (Fe3+) fluorescence chemosensor was designed and synthesized via microwave reaction based on rhodamine derivative. This sensor displayed a favorable selectivity for Fe3+ ion over a range of other common metal cations in acetonitrile/Tris buffer (4:1, v/v, pH 7.0) with a 1:1 stoichiometry, leading to prominent fluorescence OFF–ON switching of the rhodamine fluorophore. The association constant between the sensor and Fe3+ was determined to be 1.51×105, and the corresponding detection limit was calculated to be 3.2×10−7 M according to fluorescence titration analysis. The recognizing behavior of the chemosensor toward Fe3+ has been investigated in detail by FTIR, NMR, and HRMS measurements. Additionally, the recognition process of the chemosensor for Fe3+ is chemically reversible on the addition of phosphate anion (PO43−).

New diplosporin and agistatine derivatives produced by the fungal endophyte Xylaria sp. isolated from Vitis labrusca

A Xylaria sp. was isolated as an endophyte from a surface-sterilized Concord grape leaf (Vitis labrusca). Dereplication and LC–MS analysis of the filtrate extracts identified two new structures, compound 1, 13-O-methyl-(5R) diplosporin, and 2 a new agistatine. Additionally, five known compounds 3–7 including an agistatine, coriloxin, (5R)-diplosporin, and two mellein derivatives were also isolated. This is the first report of these structurally-related metabolites isolated from the same fungus, suggesting they share a related biosynthesis. Metabolites were isolated using liquid chromatography-solid phase extraction (LC-SPE) and semi-preparative HPLC. Structures were elucidated on the basis of 1D and 2D NMR analysis, HRMS measurements and X-ray structural analysis for compound 1.

Microwave-assisted coupling reaction of N-aryl sydnones with 2-nitromethylenethiazolidine: unexpected formation of (Z)-2-(nitro((E)-p-substitutedphenyldiazenyl)methylene)thiazolidines.

Reaction of N-aryl sydnones with 2-nitromethylenethiazolidine straightforwardly gives rise to the formation of (Z)-2-(nitro((E)-p-substitutedphenyldiazenyl)methylene)thiazolidines in xylene and dimethoxyethane under microwave irradiation. A meaningful and plausible mechanism for this transformation is proposed, which anticipates the extrusion of an aceto-lactone-like moiety before a coupling occurs. The structures of all the new compounds were identified on the basis of the data obtained from the NMR, IR, X-ray diffraction spectra, HRMS measurements, and physical characteristics.

Stable Isotope Dilution Analysis of Small Molecules with Carboxylic Acid Functions Using 18O Labeling for HPLC-ESI-MS/MS: Analysis of Fumonisin B1

(18)O labeling is a well-known method for the stable isotope labeling of proteins and peptides. This study describes a modified procedure for using (18)O labeling on small molecules. Fumonisin B1, a worldwide occurring mycotoxin, which is routinely analyzed by HPLC-MS/MS, was chosen as model compound. (18)O labeling was achieved by acid-catalyzed oxygen exchange from H2(18)O. A mixture of different isotopologues was obtained from the exchange, which, however, could be used as an internal standard for HPLC-MS/MS analysis. The identity of the (18)O-labeled fumonisin B1 was confirmed by NMR and HRMS measurements. The applicability as internal standard has been verified by comparison of results obtained from the method described in this paper to results obtained by reference methods. The presented method is of special interest as the (18)O labeling can be generally applied to a large group of small molecules containing carboxylic groups.

Synthesis, cytotoxicity and DNA-binding properties of Pd(II), Cu(II) and Zn(II) complexes with 4′-(4-(2-(piperidin-1-yl)ethoxy)phenyl)-2,2′:6′,2″-terpyridine

Pd(II), Cu(II) and Zn(II) complexes (1–3) based on 4′-(4-(2-(piperidin-1-yl)ethoxy)phenyl)-2,2′:6′,2″-terpyridine were synthesized and characterized by UV, IR, NMR, EPR, HRMS, elemental analyses, and molar conductivity measurements. The cytotoxicity of these complexes against HL-60, BGC-823, KB, Bel-7402, A549, Hela, K562 and MCF-7 cell lines in vitro was measured by MTT method. The DNA binding property of the complexes was evaluated by UV, fluorescence, CD spectroscopies and thermal denaturation. The cytotoxicity of complexes 1 and 3 against all the tested cell lines is better than that of cisplatin. Complexes 1 and 2 exhibit 7- and 4-folds higher cytotoxicity than cisplatin against Bel-7402 cell line. Complex 3 displays the highest cytotoxicity against all the cell lines tested, and shows 7-, 14-, 8-, 11- and 8-folds higher cytotoxicity than cisplatin against Bel-7402, A549, Hela, K562 and MCF-7 cell lines. The complexes bind to DNA via intercalation mode and complex 3 stabilizes the G-quadruplex. The results reveal that all the complexes display high cytotoxicity against all the tested cancer cell lines, and complex 3 is selective for G-quadruplex over duplex DNA.

Flexible dye-sensitized ZnO quantum dots solar cells

ZnO QDs were successfully synthesized by using a simple synthetic route. The synthesized ZnO QDs have different shapes with highly crystalline nature and their size was found to be ca. 3–5 nm. At the same time, a series of modified N719 dyes were obtained via ion-exchange reactions and characterized by FTIR and HRMS measurements. When the modified N719 dyes were used as a sensitizer for ZnO QDs-based flexible solar cells, the photovoltaic properties were enhanced significantly. A highest efficiency of 2.94% was achieved; this might be attributed to the fact that the aggregate of Zn2+/dye on the surface of ZnO QDs can be suppressed efficiently owing to a less carboxylated (COOH) bipyridyl ligand in the modified N719 dye, inhibiting the formation of chelation between ZnO QDs and dye.

Highly selective colorimetric sensing of cyanide based on formation of dipyrrin adducts

Cyanide sensing has attracted increasing interest due to its toxicity and wide use in industrial activities. Herein, we developed three colorimetric cyanide sensors by the modification of the α-position of a dipyrrin chromophore with various carbonyl groups, namely, C(6)F(5)CO, C(6)H(5)CO and CHO for 1, 2 and 3, respectively. In dichloromethane, these sensors respond to both CN(-) and F(-) with distinct colour changes. UV-Vis, (1)H NMR and HRMS measurements imply a two-process interaction between the sensors and CN(-). Initially, CN(-) forms a hydrogen bond with the NH moiety, and then it attacks the carbonyl group of the sensors via a nucleophilic addition reaction. In contrast, in aqueous systems, only cyanide induced vivid solution colour changes from light yellow to pink via nucleophilic addition reactions. The CN(-) detection limits reach a micromolar level of 3.6 × 10(-6) M, 4.2 × 10(-6) M and 7.1 × 10(-6) M for 1, 2 and 3, respectively. In view of the easy synthesis and the highly selective recognition of CN(-) with vivid colour changes, 1-3 may be developed as a novel and promising prototype of selective and sensitive colorimetric cyanide sensors.

Secondary metabolites from Spirotropis longifolia (DC) Baill and their antifungal activity against human pathogenic fungi

A phytochemical study of the ethyl acetate extract of the roots and adventitious roots of Spirotropis longifolia, a monodominant tree species of the Guianan rainforest, has allowed the isolation of three compounds: 2-hydroxy-8,9-methylenedioxy-2′,2′-dimethylpyrano-[5′,6′:4,3]-6a-prenyl-[6aS,11aS]-pterocarpan (spirotropin A), 2-hydroxy-8,9-methylenedioxy-2′,2′-dimethyl-3′,4′-dihydropyrano-[5′,6′:4,3]-6a-prenyl-[6aS,11aS]-pterocarpan (spirotropin B), and 5,7-dihydroxy-6,8-diprenyl-2⁗,2⁗-dimethylpyrano[5⁗,6⁗: 3′,4′]-isoflavone (spirotropone). In addition, 10 known compounds, trans-oxyresveratrol, trans-resveratrol, piceatannol, daidzein, genistein, isoprunetin, lupeol, latifolol, gnetin D and gnetin E, were also isolated. These compounds were evaluated for their antifungal activity and their cytotoxicity, and their structures were established by 1D and 2D NMR, HRMS, CD and optical rotation measurements.

Novel 5,6‐Dihydropyrrolo[2,1‐a]isoquinolines as Scaffolds for Synthesis of Lamellarin Analogues

As core skeletons of lamellarins: 5,6-Dihydropyrrolo[2,1-a]isoquinolines are one of the important alkaloids that exhibit significant biological activities, in this study, an efficient synthetic route was described for two novel compounds, 5,6-dihydropyrrolo[2,1-a]isoquinolines I and II. Compound I was synthesized from isovanillin with 28.3% overall yield by a six-step reaction while II from 2-(3, 4-dimethoxyphenyl) ethanamine was with 61.6% overall yield by a three-step reaction. And the structures of these two compounds were confirmed by means of IR spectrum, 1H NMR, 13C NMR, MS, HRMS, and melting point measurements.

Antioxidant Activity of Isoacteoside from Clerodendron Trichotomum

The antioxidant properties of isoacteoside, isolated from Clerodendron trichotomum (Verbenaceae), were investigated. This compound scavenged intracellular reactive oxygen species (ROS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and prevented lipid peroxidation. This radical scavenging activity of isoacteoside protected cell viability of Chinese hamster lung fibroblast (V79-4) cells exposed to hydrogen peroxide (H2O2). Furthermore, isoacteoside reduced the apoptotic cells formation induced by H2O2, as demonstrated by the decreased number of sub-G1hypo-diploid cells and apoptotic cell body formation. However, isoacteoside increased the activities of cellular antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT). Taken together, these findings suggest that isoacteoside, isolated from C. trichotomum, possesses antioxidant properties. This study was supported by a grant from the Korea Health 21 R&D Project, Ministry of Health and Welfare, Republic of Korea (01-PJ2-PG6-01NA01-002). Our thanks are due to staff of the Korea Basic Science Institute for NMR (500 MHz) and HR-MS measurements. Sam Sik Kang and Jin Won Hyun contributed equally to this study.

DETERMINATION OF HETEROATOM COMBINATIONS IN MIDDLE DISTILLATES BY HIGH RESOLUTION MASS SPECTROMETRY

ABSTRACT 70 eV electron impact HRMS has been applied to monitor heteroatom combinations present in middle distillates. Three fractions containing hetero compounds of different polarity were separated from a middle distillate and their spectra were recorded. Because the concentration of single heterocompounds in these complex mixtures is low, 70 eV were used to improve the sensitivity. A dynamic resolution of 10000 was sufficient to separate peaks of different heteroatom combinations The measured peaks were assigned to the heteroclasses O, O2, O3, S, S2, SO, N, N2, NO, NS, NO2, and NOS using a Fortran program developed for this purpose. This evaluation summarizes the results of HRMS measurements to get a quick overview over classes of heterocompounds in mineral oil products.