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Artykuły w czasopismach na temat „13C NMR identification”

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Data publikacji: 29 marca 2023

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1

S. Clendinen, Chaevien, Gregory S. Stupp, Bing Wang, Timothy J. Garrett i Arthur S. Edison. "13C Metabolomics: NMR and IROA for Unknown Identification". Current Metabolomics 4, nr 2 (30.06.2016): 116–20. http://dx.doi.org/10.2174/2213235x04666160407212156.

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2

Chamberlain, Paul H. "Identification of an Alcohol with 13C NMR Spectroscopy". Journal of Chemical Education 90, nr 10 (20.09.2013): 1365–67. http://dx.doi.org/10.1021/ed300833s.

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3

Buděšínský, Miloš, i David Šaman. "Identification of acyl groups occurring in sesquiterpene lactones: Proton and carbon-13 NMR study". Collection of Czechoslovak Chemical Communications 52, nr 2 (1987): 453–75. http://dx.doi.org/10.1135/cccc19870453.

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Characteristic 1H NMR parameters of 88 acyl groups, hitherto found as ester substituents in natural sesquiterpenic lactones, were determined from the measured spectra as well as literature data. Characteristic 13C NMR chemical shifts for 45 acyl groups were obtained in the same way; for the remaining acyls with hitherto unknown 13C NMR data the values were calculated on the basis of semiempirical relationships.
4

Střešinková, Dagmar, František Halmo i Tibor Liptaj. "Computer Assisted 13C NMR Identification of Components of Complex Organic Mixtures: Byproducts in the Manufacture of Cyclohexanone". Collection of Czechoslovak Chemical Communications 57, nr 10 (1992): 2095–99. http://dx.doi.org/10.1135/cccc19922095.

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Carbon-13 nuclear magnetic resonance is used to identify components of the distillation residue from the manufacture of cyclohexanone. 13C NMR spectra of rectification fractions provide the data utilized in an algorithm to extract subspectrum resonances specific to each component of the mixture. The subspectra are then subjected to search in 13C NMR library of potential components. A number of components were unambiguously identified in original sample even if moderate peak overlaps occurred. Generated subspectra made also possible identification of substances which are not present in 13C NMR libraries.
5

Ferrante, Laura, Kashif Rajpoot, Mark Jeeves i Christian Ludwig. "Automated analysis for multiplet identification from ultra-high resolution 2D-1H,13C-HSQC NMR spectra". Wellcome Open Research 7 (14.10.2022): 262. http://dx.doi.org/10.12688/wellcomeopenres.18248.1.

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Background: Metabolism is essential for cell survival and proliferation. A deep understanding of the metabolic network and its regulatory processes is often vital to understand and overcome disease. Stable isotope tracing of metabolism using nuclear magnetic resonance (NMR) and mass spectrometry (MS) is a powerful tool to derive mechanistic information of metabolic network activity. However, to retrieve meaningful information, automated tools are urgently needed to analyse these complex spectra and eliminate the bias introduced by manual analysis. Here, we present a data-driven algorithm to automatically annotate and analyse NMR signal multiplets in 2D-1H,13C-HSQC NMR spectra arising from 13C -13C scalar couplings. The algorithm minimises the need for user input to guide the analysis of 2D-1H,13C-HSQC NMR spectra by performing automated peak picking and multiplet analysis. This enables non-NMR specialists to use this technology. The algorithm has been integrated into the existing MetaboLab software package. Methods: To evaluate the algorithm performance two criteria are tested: is the peak correctly annotated and secondly how confident is the algorithm with its analysis. For the latter a coefficient of determination is introduced. Three datasets were used for testing. The first was to test reproducibility with three biological replicates, the second tested the robustness of the algorithm for different amounts of scaling of the apparent J-coupling constants and the third focused on different sampling amounts. Results: The algorithm annotated overall >90% of NMR signals correctly with average coefficient of determination ρ of 94.06 ± 5.08%, 95.47 ± 7.20% and 80.47 ± 20.98% respectively. Conclusions: Our results indicate that the proposed algorithm accurately identifies and analyses NMR signal multiplets in ultra-high resolution 2D-1H,13C-HSQC NMR spectra. It is robust to signal splitting enhancement and up to 25% of non-uniform sampling.
6

Kartashov, V. S. "13C NMR identification of drugs based on pyridine derivatives". Pharmaceutical Chemistry Journal 33, nr 2 (luty 1999): 113. http://dx.doi.org/10.1007/bf02508121.

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7

Lizotte, Pauline A., i Jonathan E. Poulton. "Identification of (R)-Vicianin in Davallia trichomanoides Blume". Zeitschrift für Naturforschung C 41, nr 1-2 (1.02.1986): 5–8. http://dx.doi.org/10.1515/znc-1986-1-202.

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Abstract The cyanogenic glycoside of young fronds and fiddleheads of the fern Davallia trichomanoides Blume was identified as (R)-vicianin (the β-vicianoside of (R)-mandelonitrile) by acid and enzymic hydrolysis, 1H-NMR and 13C-NMR spectroscopy, and by comparison with an authentic sample isolated from Vicia angustifolia seeds.
8

Meese, Claus O., i Peter Fischer. "Tracing the Human Metabolism of Stable Isotope-Labelled Drugs by ex vivo NM R Spectroscopy A Revision of S-Carboxymethyl-ʟ-cysteine Biotransformation". Zeitschrift für Naturforschung C 45, nr 11-12 (1.12.1990): 1171–75. http://dx.doi.org/10.1515/znc-1990-11-1215.

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A direct structural identification, and quantitative assessment below the 50 nmol/ml level, of the full pattern of renally excreted metabolites is made possible by 13C NMR measurements of untreated urine samples when stable isotope-labelled (13C) drug analogues are administered to humans. The full potential of the new ex vivo NMR approach is exemplified by a study, for a group of volunteers, of S-carboxymethyl-ʟ-cysteine metabolism. The metabolic sulphoxidation pathway of S-Carboxymethyl-ʟ-cysteine in man, accepted so far, needs to be profoundly revised on the basis of the 13C NMR results.
9

Eshimbetov, Alisher, Shahobiddin Adizov, Inderpreet Kaur i Akhmed Reymov. "Is it possible to differentiate between 2-phenylaminodihydro-1,3-thiazine from 2-phenyliminotetrahydro-1,3-thiazine by spectral methods? New glance to the old problem". European Journal of Chemistry 12, nr 1 (31.03.2021): 77–80. http://dx.doi.org/10.5155/eurjchem.12.1.77-80.2068.

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Several studies have reported the presence of amine and imine tautomeric forms for hydrogenated 1,3-thiazine derivatives. However, identification of their tautomeric forms by UV, FTIR and mass-spectral methods does not yield expected results. Here, we report the synthesis of 2-phenylaminodihydro-1,3-thiazine and 2-phenyliminotetrahydro-1,3-thiazine and the analysis of their UV, FTIR and NMR (1H and 13C) spectral data. An identical picture of UV spectra was recorded for both compounds. However, distinctive characteristics were found in the FTIR, 1H and 13C NMR spectra. The C=N band of amine form was observed in higher frequency region relative to imine form. The signal of C2 carbon of amine form in 13C NMR spectrum was occurred in more downfield (δ 165.3 ppm) relative to C2 signal of imine form (δ 152.1 ppm). In addition, the difference between C2 and C8 carbon signals of amine form was very high (Δδ = 30.6 ppm) relative to imine form (δ 5.4 ppm). The position of C2 and C8 signals and the difference between them in 13C NMR spectrum was found to be more promising in identification of tautomeric forms in case of hydrogenated 1,3-thiazine derivatives.
10

Moiseev, S. V., N. E. Kuz’mina i A. I. Luttseva. "Development of Identification Test Methods for Triptorelin Acetate and Goserelin Acetate Substances using NMR spectroscopy". Bulletin of the Scientific Centre for Expert Evaluation of Medicinal Products 9, nr 1 (25.03.2019): 54–63. http://dx.doi.org/10.30895/1991-2919-2019-9-1-54-63.

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The work is a continuation of the research on the use of NMR spectroscopy in the quality control of natural peptide hormone-based active substances and their synthetic analogues.The aimof the paper was to develop identification test methods for triptorelin acetate and goserelin acetate substances using NMR spectroscopy that does not require reference standards ‒ with the aim of using the newly developed test methods in pharmacopoeial analysis.Materials and methods:the procedure was developed using two-dimensional NMR spectroscopy (1H-1H gCOSY,1H-13C gHSQC,1H-13C gHMBC).Results:thestudy made it possible to assign1H and13C NMR signals to a specific molecular fragment, and to determine the amino acid composition of each oligopeptide.Conclusions:the authors drew up a table showing structural assignment of NMR signals, which makes it possible to use the NMR method for identification testing of triptorelin acetate and goserelin acetate substances without the use of pharmacopoeial reference standards. The study helped to determine the optimal temperature conditions for recording13C NMR spectra (27 °С and 50 °С for triptorelin acetate and goserelin acetate, respectively). It was demonstrated that13C NMR spectroscopy could be used for identification testing in pharmacopoeial analysis.
11

Canton, Marine, Jane Hubert, Stéphane Poigny, Richard Roe, Yves Brunel, Jean-Marc Nuzillard i Jean-Hugues Renault. "Dereplication of Natural Extracts Diluted in Glycerin: Physical Suppression of Glycerin by Centrifugal Partition Chromatography Combined with Presaturation of Solvent Signals in 13C-Nuclear Magnetic Resonance Spectroscopy". Molecules 25, nr 21 (31.10.2020): 5061. http://dx.doi.org/10.3390/molecules25215061.

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For scientific, regulatory, and safety reasons, the chemical profile knowledge of natural extracts incorporated in commercial cosmetic formulations is of primary importance. Many extracts are produced or stabilized in glycerin, a practice which hampers their characterization. This article proposes a new methodology for the quick identification of metabolites present in natural extracts when diluted in glycerin. As an extension of a 13C nuclear magnetic resonance (NMR) based dereplication process, two complementary approaches are presented for the chemical profiling of natural extracts diluted in glycerin: A physical suppression by centrifugal partition chromatography (CPC) with the appropriate biphasic solvent system EtOAc/CH3CN/water 3:3:4 (v/v/v) for the crude extract fractionation, and a spectroscopic suppression by presaturation of 13C-NMR signals of glycerin applied to glycerin containing fractions. This innovative workflow was applied to a model mixture containing 23 natural metabolites. Dereplication by 13C-NMR was applied either on the dry model mixture or after dilution at 5% in glycerin, for comparison, resulting in the detection of 20 out of 23 compounds in the two model mixtures. Subsequently, a natural extract of Cedrus atlantica diluted in glycerin was characterized and resulted in the identification of 12 metabolites. The first annotations by 13C-NMR were confirmed by two-dimensional NMR and completed by LC-MS analyses for the annotation of five additional minor compounds. These results demonstrate that the application of physical suppression by CPC and presaturation of 13C-NMR solvent signals highly facilitates the quick chemical profiling of natural extracts diluted in glycerin.
12

Kuz’mina, Natalia E., Sergey V. Moiseev, Elena Y. Severinova, Evgenii A. Stepanov i Natalia D. Bunyatyan. "Identification and Quantification by NMR Spectroscopy of the 22R and 22S Epimers in Budesonide Pharmaceutical Forms". Molecules 27, nr 7 (31.03.2022): 2262. http://dx.doi.org/10.3390/molecules27072262.

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The authors developed four variants of the qNMR technique (1H or 13C nucleus, DMSO-d6 or CDCl3 solvent) for identification and quantification by NMR of 22R and 22S epimers in budesonide active pharmaceutical ingredient and budesonide drugs (sprays, capsules, tablets). The choice of the qNMR technique version depends on the drug excipients. The correlation of 1H and 13C spectra signals to molecules of different budesonide epimers was carried out on the basis of a comprehensive analysis of experimental spectral NMR data (1H-1H gCOSY, 1H-13C gHSQC, 1H-13C gHMBC, 1H-1H ROESY). This technique makes it possible to identify budesonide epimers and determine their weight ratio directly, without constructing a calibration curve and using any standards. The results of measuring the 22S epimer content by qNMR are comparable with the results of measurements using the reference HPLC method.
13

Garcia, Gabriel, Delphin Rabehaja, Julie-Marie Charmillon, Panja Ramanoelina, Joseph Casanova i Félix Tomi. "Integrated Analysis of the Bark Oil from Cinnamosma madagascariensis by GC(RI), GC-MS and NMR. 13C NMR data of Cyclocopacamphene and Cyclosativene". Natural Product Communications 12, nr 2 (luty 2017): 1934578X1701200. http://dx.doi.org/10.1177/1934578x1701200235.

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The composition of leaf and bark oils of Cinnamosma madagascariensis has been investigated by a combination of GC (RI), GC-MS and 13C NMR. The leaf oil contained mainly monoterpenes: myrcene (17.9%), limonene (17.8%), β-phellandrene (15.3%) and linalool (12.2%). The bark oil, investigated for the first time, contained β-pinene (49.9%) and α-pinene (19.5%) as major components. Special attention was paid to the identification of cyclocopacamphene, an epimer of cyclosativene. 13C NMR data of both compounds have been provided.
14

Vijay, Dhanya, Nassra S. Alshamsi, Ziad Moussa i M. Kalim Akhtar. "Extraction of the Anticancer and Antimicrobial Agent, Prodigiosin, from Vibrio gazogenes PB1 and Its Identification by 1D and 2D NMR". Molecules 27, nr 18 (16.09.2022): 6030. http://dx.doi.org/10.3390/molecules27186030.

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Prodigiosin is a secondary metabolite produced in several species of bacteria. It exhibits antimicrobial and anticancer properties. Methods for the extraction and identification of prodigiosin and their related derivatives from bacterial cultures typically depend on solvent-based extractions followed by NMR spectroscopy. The estuarine bacterium, V. gazogenes PB1, was previously shown to produce prodigiosin. This conclusion, however, was based on analytical data obtained from ultraviolet-visible absorption spectrophotometry and infrared spectroscopy. Complete dependence on these techniques would be considered inadequate for the accurate identification of the various members of the prodiginine family of compounds, which possess very similar chemical structures and near-identical optical properties. In this study, we extracted prodigiosin from a culture of Vibrio gazogenes PB1 cultivated in minimal media, and for the first time, confirmed the synthesis of prodigiosin Vibrio gazogenes PB1 using NMR techniques. The chemical structure was validated by 1H and 13C NMR spectroscopy, and further corroborated by 2D NMR, which included 1H-1H-gDQFCOSY, 1H-13C-gHSQC, and 1H-13C-gHMBC, as well as 1H-1H-homonuclear decoupling experiments. Based on this data, previous NMR spectral assignments of prodigiosin are reaffirmed and in some cases, corrected. The findings will be particularly relevant for experimental work relating to the use of V. gazogenes PB1 as a host for the synthesis of prodigiosin.
15

KINOSHITA, Haruki, Yasuo TOHIRA, Hiroshi SUGIYAMA i Mikio SAWADA. "Use of 13C-NMR Spectroscopy for Detection and Identification of Labile Metabolites of 13C-labeled Inabenfide". Journal of Pesticide Science 12, nr 2 (1987): 261–63. http://dx.doi.org/10.1584/jpestics.12.261.

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16

Irmawan, Muhammad, Frederyk Mandey i Seniwati Dali. "Isolation, Identification, Characteriterization, And Toxicity Essay Of Non-polar Secondary Metabolite Fraction From Ageratum conyzoides L". Indo. J. Chem. Res. 6, nr 1 (31.07.2018): 513–17. http://dx.doi.org/10.30598//ijcr.2018.6.1.

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Ageratum Conyzoides L. has a toxic and bioactive component as anti-cancer and especially for the root, it has anti-tumor. In order to figure out the active component, it is necessary to do four steps; isolation, identification, characterization, and toxicity essay Brine Shrimp Lethality Test (BSLT) of non-polar fraction Ageratum conyzoides L plant. Isolation method consist of four parts; extraction, partitioning of Kupchan method, fractionation, and purification. Fractionation method uses press column chromatography (KTT). Furthermore, purification process uses thin layer chromatography (TLC) and characterization with spectroscopy FTIR, 1H-NMR and 13C-NMR. Then characterization utilizes spectroscopy FTIR, 1H-NMR and 13C-NMR. The toxicity essay toward Artemia Salina Leach n-hexane fraction and dichloromethane fraction showed that the fraction had toxic properties with number of LC50 are 0,0237 and 4,642 µg/mL respectively. Moreover, n-hexane fraction has succeed in isolating Stigmasterol compound shaped white crystalline needles with 19.6 mg weight, 143-144 °C melting point and and had toxic properties with number of LC50 are 30,33 µg/mL.
17

Irmawan, Muhammad, Frederyk Mandey i Seniwati Dali. "Isolation, Identification, Characteriterization, And Toxicity Essay Of Non-polar Secondary Metabolite Fraction From Ageratum conyzoides L". Indo. J. Chem. Res. 6, nr 1 (31.07.2018): 513–17. http://dx.doi.org/10.30598/v12.

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Ageratum Conyzoides L. has a toxic and bioactive component as anti-cancer and especially for the root, it has anti-tumor. In order to figure out the active component, it is necessary to do four steps; isolation, identification, characterization, and toxicity essay Brine Shrimp Lethality Test (BSLT) of non-polar fraction Ageratum conyzoides L plant. Isolation method consist of four parts; extraction, partitioning of Kupchan method, fractionation, and purification. Fractionation method uses press column chromatography (KTT). Furthermore, purification process uses thin layer chromatography (TLC) and characterization with spectroscopy FTIR, 1H-NMR and 13C-NMR. Then characterization utilizes spectroscopy FTIR, 1H-NMR and 13C-NMR. The toxicity essay toward Artemia Salina Leach n-hexane fraction and dichloromethane fraction showed that the fraction had toxic properties with number of LC50 are 0,0237 and 4,642 µg/mL respectively. Moreover, n-hexane fraction has succeed in isolating Stigmasterol compound shaped white crystalline needles with 19.6 mg weight, 143-144 °C melting point and and had toxic properties with number of LC50 are 30,33 µg/mL.
18

Hung, Nguyen Huy. "CHEMICAL CONSTITUENTS FROM THE SEEDS OF ANNONA RETICULATA L. IN VIETNAM". Vietnam Journal of Science and Technology 54, nr 4A (21.03.2018): 221. http://dx.doi.org/10.15625/2525-2518/54/4a/11997.

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In the present study, the chemical investigation of the seeds of A. reticulata L. (Annonaceae) in Vietnam has resulted in the identification of four known compounds, including two triterpenoids (rotundic acid (1), pedunculoside (2)), and two phenolic compounds (eleutheroside B (3), sinapaldehyde glucoside (4). Their chemical structures were elucidated on the basis of spectroscopic analysis, including homonuclear and heteronuclear correlation NMR (1H-NMR, 13C-NMR, COSY, HSQC, and HMBC) experiments.
19

Kanzari-Mnallah, Dorra, Med L. Efrit, Jiří Pavlíček, Frédéric Vellieux, Habib Boughzala i Azaiez B. Akacha. "Synthesis, Conformational Analysis and Crystal Structure of New Thioxo, Oxo, Seleno Diastereomeric Cyclophosphamides Containing 1,3,2-dioxaphosphorinane". Current Organic Chemistry 23, nr 2 (23.04.2019): 205–13. http://dx.doi.org/10.2174/1385272823666190213142748.

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Thioxo, Oxo and Seleno diastereomeric cyclophosphamides containing 1,3,2- dioxaphosphorinane are prepared by a one-step chemical reaction. Their structural determination is carried out by means of Nuclear Magnetic Resonance NMR (31P, 1 H, 13C) and High-Resolution Mass Spectroscopy (HRMS). The conformational study of diastereomeric products is described. Density Functional Theory (DFT) calculations allowed the identification of preferred conformations. Experimental and calculated 31P, 13C, 1H NMR chemical shifts are compared. The molecular structure of the 2-Benzylamino-5-methyl-5- propyl-2-oxo-1,3,2-dioxaphosphorinane (3d) has been determined by means of crystal Xray diffraction methods.
20

Bakibaev, A. A., М. Zh Sadvakassova, R. Sh Еrkasov i А. Е. Аtagulova. "Identification and analysis of N-alkyl-N’-arylalkylureas by nuclear magnetic resonance". BULLETIN of the L.N. Gumilyov Eurasian National University. Chemistry. Geography. Ecology Series 130, nr 1 (2020): 18–22. http://dx.doi.org/10.32523/2616-6771-2020-130-1-18-22.

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This paper presents the results that allow one to reliably identify N-alkyl- (10 compounds) and N-alkyl-N’- arylalkylureas (12 compounds) based on the data of 1H and 13C nuclear magnetic resonance (NMR) methods. A systematic analysis has been carried out of chemical shifts in the NMR spectra of the compounds. Additionally, the authors have investigated the effect of the nitrogen atoms substituents on the chemical shifts in the NH2, NH, and C = O groups of urea.
21

Zabala, Myrnille Joy B., Lolita G. Lagurin i Fabian M. Dayrit. "13C Nuclear Magnetic Resonance Phytochemical Profiling of the In Vitro Antidiabetic Potential of Vitex negundo L." Abstract Proceedings International Scholars Conference 4, nr 1 (16.08.2019): 181. http://dx.doi.org/10.35974/isc.v4i1.1652.

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Vitex negundo has been known since ancient times as a medicinal plant. The objective of this study is to investigate the effect of methanol and ethanol extracts, and ethyl acetate, chloroform and aqueous fractions of Vitex negundo using an in vitro model to test glucose diffusion and to determine the phytochemical profile of the extracts and fractions using 13C nuclear magnetic resonance (NMR) spectroscopy. The chloroform fractions, ethyl acetate-EtOH and ethyl acetate-MeOH gave the highest inhibitory effect on both the diffusion activities in vitro. Retardation of glucose diffusion suggests that negundo has the potential to lower postprandial glucose. Correlation analysis of the 13C NMR profile with retardation activity suggests that compounds containing glycosidic residues may be responsible for the glucose retardation activity. This is the first example where activity has been correlated with specific structural features of compounds from a crude extract using 13C NMR chemical shifts to assist in the identification of active compounds.
22

Mesilaakso, Markku, Eeva-Liisa Tolppa i Paula Nousiainen. "Analysis of 1H and 13C{1H} NMR Spectral Parameters of Diphenylchloroarsine, Diphenylcyanoarsine, and 10-Chloro- 5,10-Dihydrophenarsazine: Identification of the Compounds through Reference to Simulated Spectra". Applied Spectroscopy 51, nr 5 (maj 1997): 733–37. http://dx.doi.org/10.1366/0003702971940891.

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The 1H and 13C{1H} nuclear magnetic resonance (NMR) spectra of diphenylchloroarsine, diphenylcyanoarsine, and 10-chloro-5,10-dihydrophenarsazine were recorded from samples prepared in CDCl3, CD2Cl2, and (CD3)2CO. Spectra were analyzed, and detailed 1H NMR spectral parameters were determined by iterative analysis. Simulation of spectra and their use as reference spectra for identification of the compounds under different conditions are discussed.
23

Keller, Julia, Luisa Hantschke, Hajo Haase i Matthias Koch. "Synthesis and Structural Identification of a Biaryl Ether-Linked Zearalenone Dimer". Molecules 23, nr 10 (12.10.2018): 2624. http://dx.doi.org/10.3390/molecules23102624.

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A new dimer of the food-relevant mycotoxin zearalenone was isolated after electrochemical and chemical oxidation. The structure was determined as a 16-O-15′-biaryl ether-linked dimer based on spectroscopic analyses (1H- and 13C-NMR, COSY, HMBC, and HSQCAD) and high-resolution mass spectrometry analysis (Q-TOF).
24

Nyigo, Vitus A., Hamisi M. Malebo, Faith Mabiki i Robinson Mdegela. "Isolation and identification of long -chain aliphatic compounds from Synadenium glaucescens". Journal of Phytopharmacology 11, nr 3 (25.06.2022): 151–54. http://dx.doi.org/10.31254/phyto.2022.11303.

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Purification of dichloromethane extract from root barks and leaves of Synadenium glaucescens extracts through chromatographic techniques resulted into the isolation of two compounds, namely erythrinacinate C and 1-octacosanol. Chemical structures were established mainly using both one and two dimensional 1H and 13C NMR data and by comparison of the current NMR data with those from literature. Mass spectrophotometry data were used for confirmation through molecular ion peak. Both compounds are known to have been isolated from other plant species but are being reported from this plant species for the first time.
25

Ouattara, Zana A., Jean Brice Boti, Coffy Antoine Ahibo, Félix Tomi, Joseph Casanova i Ange Bighelli. "Combined Analysis of the Root Bark Oil of Cleistopholis glauca by Chromatographic and Spectroscopic Techniques". Natural Product Communications 8, nr 12 (grudzień 2013): 1934578X1300801. http://dx.doi.org/10.1177/1934578x1300801231.

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The composition of root bark oil from Cleistopholis glauca Pierre ex Engler & Diels growing wild in Ivory Coast was investigated by GC (in combination with retention indices) and 13C NMR spectroscopy after partition of hydrocarbons and oxygenated compounds on silica gel. Thirty-one compounds have been identified. C. glauca produces a sesquiterpene-rich oil, patchoulenone (33.5%), cyperene (9.5%) and germacrene D (6.6%) being the main components. Special attention was paid to the identification and quantification of germacrene C (a heat-sensitive compound) and δ-elemene, which were achieved by a combination of GC(FID) and 13C NMR spectroscopy. The composition of C. glauca root bark and leaf oils differed drastically.
26

Becette, Owen B., Guanghui Zong, Bin Chen, Kehinde M. Taiwo, David A. Case i T. Kwaku Dayie. "Solution NMR readily reveals distinct structural folds and interactions in doubly 13C- and 19F-labeled RNAs". Science Advances 6, nr 41 (październik 2020): eabc6572. http://dx.doi.org/10.1126/sciadv.abc6572.

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RNAs form critical components of biological processes implicated in human diseases, making them attractive for small-molecule therapeutics. Expanding the sites accessible to nuclear magnetic resonance (NMR) spectroscopy will provide atomic-level insights into RNA interactions. Here, we present an efficient strategy to introduce 19F-13C spin pairs into RNA by using a 5-fluorouridine-5′-triphosphate and T7 RNA polymerase–based in vitro transcription. Incorporating the 19F-13C label in two model RNAs produces linewidths that are twice as sharp as the commonly used 1H-13C spin pair. Furthermore, the high sensitivity of the 19F nucleus allows for clear delineation of helical and nonhelical regions as well as GU wobble and Watson-Crick base pairs. Last, the 19F-13C label enables rapid identification of a small-molecule binding pocket within human hepatitis B virus encapsidation signal epsilon (hHBV ε) RNA. We anticipate that the methods described herein will expand the size limitations of RNA NMR and aid with RNA-drug discovery efforts.
27

KAWAI, Shigeru, Kanzo SAKATA, Akihito YAGI i Kazuo INA. "Identification of New Constituents of Cider Vineger by 13C-NMR Spectroscopic Study." Agricultural and Biological Chemistry 55, nr 10 (1991): 2633–35. http://dx.doi.org/10.1271/bbb1961.55.2633.

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Chalmers, A. A., i P. Perlstein. "Identification of hardeners in solid epoxy resins by high-resolution 13C-NMR". European Polymer Journal 23, nr 11 (styczeń 1987): 887–90. http://dx.doi.org/10.1016/0014-3057(87)90063-2.

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29

do Nascimento Marinho, Rosiane Ferreira, Bianca Roberta Peres Angrisani, Arthur Ladeira Macedo, Davyson de Lima Moreira, Carlos Magno Rocha Ribeiro, Thatyana Rocha Alves Vasconcelos i Alessandra Leda Valverde. "1H and 13C NMR Spectral Data of Neolignans Isolated from Piper Species". Current Organic Chemistry 24, nr 14 (13.10.2020): 1527–54. http://dx.doi.org/10.2174/1385272824999200608133542.

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Plants of the genus Piper (Piperaceae) have a pantropical distribution. In Brazil, Piper species are used in traditional medicine to treat many diseases such as inflammation, diabetes, toothache, and fever. Many reports have shown a correlation between the biological activities of Piper species and neolignans, a secondary metabolite class obtained from the shikimic acid biosynthetic pathway. This review aims to provide detailed information on the structural identification of neolignans isolated from Piper species by 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy. These searchable data enable rapid identification and routine analysis of neolignans from extracts of the Piper species.
30

Sauter, F., E. W. H. Hayek, W. Moche i U. Jordis. "Betulin aus archäologischem Schwelteer / Identification of Betulin in Archaeological Tar". Zeitschrift für Naturforschung C 42, nr 11-12 (1.12.1987): 1151–52. http://dx.doi.org/10.1515/znc-1987-11-1202.

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A compound obtained from an early Iron-Age wood tar via “Kugelrohr”-distillation or extraction was identified as betulin by TLC. 1H - and 13C - NMR as well as by mass spectroscopy. This result validates the assumption that birch was used for the preparation of the archaeological wood tar found at the excavation in Stillfried a .d . March. Lower Austria.
31

Nyigo, Vitus A., Xolani Peter, Faith Mabiki, Hamisi M. Malebo, Robinson H. Mdegela i Gerda Fouche. "Isolation and identification of euphol and β-sitosterol from the dichloromethane extracts of Synadenium glaucescens". Journal of Phytopharmacology 5, nr 3 (3.08.2016): 100–104. http://dx.doi.org/10.31254/phyto.2016.5302.

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Purification of dichloromethane extract from root barks and leaves of Synadenium glaucescens respectively resulted into the isolation of two compounds namely Euphol and β-sitosterol. Chemical structures were established mainly by using 1H an d 13C NMR data and by comparing current NMR data with those reported in the literature. Both compounds are known and have been isolated from other plant species but are being reported from this plant species for the first time.
32

Djié Bi, Tra Marc Gabin, Acafou Thierry Yapi, Zana Adama Ouattara, Janat Akhanovna Mamyrbekova-Békro, Mathieu Paoli, Félix Tomi, Vincent Castola i Ange Bighelli. "Composition and Variability of Leaf Oil from Monodora Crispata -13C NMR Identification of Heat-sensitive Compounds". Natural Product Communications 12, nr 3 (marzec 2017): 1934578X1701200. http://dx.doi.org/10.1177/1934578x1701200332.

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The composition of four samples of essential oil isolated from the leaves of individual Monodora crispata trees growing wild in an Ivorian forest (Adiopodoumé) were investigated by a combination of chromatographic (GC(RI)) and spectrometric (GC-MS, 13C NMR) techniques. In total, fifty-seven compounds accounting for 92.3–98.7% of the whole composition were identified. These oils were characterized by the preeminence of sesquiterpene hydrocarbons and the content of the main components varied substantially from sample to sample. Two samples were largely dominated by germacrene D (67.3% and 76.3%, respectively), a third sample was represented by germacrene D (28.3%), germacrene C (14.3%), δ-elemene (12.1%) and β-elemene (9.3%) and the fourth sample was characterized by 3-dimethylallylindole (15.1%), germacrene D (12.0%) and cyperene (7.8%). 13C NMR spectroscopy was particularly efficient for the identification of heat-sensitive compounds.
33

Marliyana, Soerya Dewi, Muhamad Widyo Wartono, Fajar Rakhman Wibowo i Gesti Munasah. "Isolasi dan Identifikasi Senyawa Seskuiterpen dari Curcuma soloensis Val. (Temu Glenyeh)". Jurnal Kimia VALENSI 4, nr 2 (30.11.2018): 137–42. http://dx.doi.org/10.15408/jkv.v4i2.7443.

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Curcuma soloensis Val. is a family plant Zingiberaceae and is known as "temu gelnyeh". This plant has been used as a medicinal plant but has not been widely reported about its chemical components. Therefore, this study was carried out to isolation and identification of the chemical components of the C. soloensis Val. rhizome. Isolation was done by extraction, fractionation, and purification. The fractionation and purification of the compound were carried out using chromatography methods. The identification of the compound was determined by spectroscopic methods including 1D-NMR (1H NMR, 13C NMR) and 2D-NMR (HSQC, HMBC). Based on NMR spectra data analysis and compared with literature, the compound obtained yellow liquid was ar-turmerone (2-methyl-6- (4-methylphenyl) hept-2-en-4-on) which was a terpenoid sesquiterpene. Ar-turmerone is the first compound that found from Curcuma soloensis Val. rhizome.
34

Saidi, Nurdin, A. Hamid A. Hadi, Khalijah Awang i Mat Ropi Mukhtar. "APHORPINE ALKALOIDS FROM BARK OF Cryptocarya ferrea". Indonesian Journal of Chemistry 9, nr 3 (24.06.2010): 461–65. http://dx.doi.org/10.22146/ijc.21516.

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Isolation, identification and characterization of the compounds isolated from the bark of Cryptocarya ferrea yielded three known aphorpine alkaloids. They are (-)-O-methylisopiline 1, (+)-norlirioferine 2 and (+)-lirioferine 3. Structural elucidation was established through several spectroscopic methods, such as 1D-NMR (1H, 13C, DEPT, NOE), 2D-NMR (COSY, NOESY, HMQC, HMBC), UV, IR, and MS and comparison with the published data. Keywords: Cryptocarya ferrea; (-)-o-methylisopiline, (+)-norlirioferine, (+)-lirioferine
35

Jankowski, C. K., M. R. Van Calsteren, N. Aychet, J. F. Dozol, C. Moulin i C. Lamouroux. "Study of the nitration of di-n-octylcrown-6 calix[4]arene using LC–MS, NMR, and molecular modelling". Canadian Journal of Chemistry 83, nr 8 (1.08.2005): 1098–113. http://dx.doi.org/10.1139/v05-126.

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The selective HNO3 nitration of di-n-octylcrown-6 calix[4]arene using different conditions, studied with LC–MS and NMR (1H and 13C) spectroscopic techniques, lead to the identification of most of the expected nitro derivative isomeric compounds. The formation of these isomers under acidic and radiolytic conditions is discussed with the help of molecular modelling.Key words: calix crown compounds, nitration of calixarenes, NMR of isomeric nitrocalixarenes, LC-ESI-MS.
36

Ribeiro, Carlos Magno Rocha, Thiago Silva Galvão de Souza, Karinne Canevalli de Almeida, Karen Danielle Borba Dutra i Alessandra Leda Valverde. "Heliannuol: Distribution, Biological Activities, 1H and 13C-NMR Spectral Data". Mini-Reviews in Organic Chemistry 17, nr 3 (28.04.2020): 309–22. http://dx.doi.org/10.2174/1570193x16666190405102658.

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: Heliannuols are an important class of compounds isolated from Helianthus annuus, a common sunflower, with allelopathic properties. Interestingly, two of these fourteen compounds have been isolated from a gorgonian, Pseudopterogorgia rigida. This review compiles data on the isolation and biological activity of heliannuols described in the literature and briefly reports the papers describing their syntheses. This review could stimulate research into other natural species and syntheses. Further, it describes the 1H and 13C-NMR spectral data described in the literature for the 14 heliannuols already isolated and correlates them with their respective structures. Therefore, we believe that these searchable data enable a rapid identification in routine analysis of the crude extracts of sunflowers or gorgonians.
37

Rumampuk, Rymond J. "IDENTIFICATION AND SEQUENCING BY NMR SPECTROSCOPY OF THE CARBOHYDRATE MOIETY IN A SAPONIN FROM Barringtonia asiatica". Indonesian Journal of Chemistry 1, nr 3 (5.06.2010): 120–24. http://dx.doi.org/10.22146/ijc.21936.

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A trisaccharide chain in a saponin from the seeds of Barringtonia asiatica has been identified and sequenced as {[b-D-galactopyranosyl(1®3)- b-D-glucopyranosyl(1®2)]-b-D-glucuronopyranosyloxy} using a combination of homonuclear and heteronuclear correlation NMR spectroscopy. The 1H and 13C NMR signals of the sugar residues can be determined and distinguished from one other by use of the HMQC-TOCSY technique. Anomeric configurations were unambiguously assigned from the vicinal coupling constants 3JH-1,H-2 of the anomeric protons. Inter-glycosidic linkage assignments were elucidated using HMBC. Keyword: Barringtonia asiatica, carbohydrate, saponin, NMR
38

Palu, Doreen, Ange Bighelli, Joseph Casanova i Mathieu Paoli. "Identification and Quantitation of Ursolic and Oleanolic Acids in Ilex aquifolium L. Leaf Extracts Using 13C and 1H-NMR Spectroscopy". Molecules 24, nr 23 (3.12.2019): 4413. http://dx.doi.org/10.3390/molecules24234413.

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Leaves of Ilex aquifolium L. have been used for their therapeutic properties. In previous studies, components contained in the leaves were first isolated by various chromatographic techniques. Then, quantitation of oleanolic and ursolic acids, which are responsible for the biological and therapeutic activities of the plant, was performed by HPLC, HPTLC, and somewhat by GC-MS. Our objective was to develop a simple method that allows the identification of compounds contained in the leaves of Corsican I. aquifolium and to quantify ursolic and oleanolic acids. Leaves were successively extracted with hexane and dichloromethane. The extracts were chromatographed on silica gel and the fractions of column chromatography submitted to 13C-NMR analysis, following a computerized method developed in the laboratory. 13C-NMR allowed the identification of various triterpenes including ursolic acid and oleanolic acid. Quantitation of both acids was achieved, for the first time, by 1H-NMR after validation of the method (accuracy, precision, linearity, limit of detection and limit of quantitation). Ursolic and oleanolic acids accounted for 55.3% and 20.8% of the dichloromethane extract, respectively. This represents 1.3% and 0.5% of the mass of dried leaves. 1H-NMR spectroscopy appeared as a powerful tool for a rapid quantitation of biologically active compounds from I. aquifolium.
39

Poulhazan, Alexandre, Alexandre Arnold, Dror Warschawski i Isabelle Marcotte. "Unambiguous Ex Situ and in Cell 2D 13C Solid-State NMR Characterization of Starch and Its Constituents". International Journal of Molecular Sciences 19, nr 12 (30.11.2018): 3817. http://dx.doi.org/10.3390/ijms19123817.

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Starch is the most abundant energy storage molecule in plants and is an essential part of the human diet. This glucose polymer is composed of amorphous and crystalline domains in different forms (A and B types) with specific physicochemical properties that determine its bioavailability for an organism, as well as its value in the food industry. Using two-dimensional (2D) high resolution solid-state nuclear magnetic resonance (SS-NMR) on 13C-labelled starches that were obtained from Chlamydomonas reinhardtii microalgae, we established a complete and unambiguous assignment for starch and its constituents (amylopectin and amylose) in the two crystalline forms and in the amorphous state. We also assigned so far unreported non-reducing end groups and assessed starch chain length, crystallinity and amylose content. Starch was then characterized in situ, i.e., by 13C solid-state NMR of intact microalgal cells. Our in-cell methodology also enabled the identification of the effect of nitrogen starvation on starch metabolism. This work shows how solid-state NMR can enable the identification of starch structure, chemical modifications and biosynthesis in situ in intact microorganisms, eliminating time consuming and potentially altering purification steps.
40

Shahriar, Mohammad Shahriar, Mohiuddin Ahmed Bhuiyan i Md Sohel Rana. "Isolation and identification of different compounds from Citrus assamensis leaf". Journal of Bangladesh Academy of Sciences 44, nr 2 (19.01.2021): 85–93. http://dx.doi.org/10.3329/jbas.v44i2.51453.

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Six coumarins, one benzene, one flavone, one acridone, one limonoid, one triterpene and two phytosterol derivatives were isolated from the methanol, ethanol and chloroform leaf extracts of Citrus assamensis. Extensive spectroscopic studies, including high field 1H NMR and 13C NMR analyses, allowed the identification of thirteen known compounds as bergapten (1), umckalin (2), citropten (3), 4-hydroxybenzaldehyde (4), bergamottin (5), β-amyrin (6), umbeliferone (7), scopoletin (8), citrusinol (9), citracridone-III (10), limonin (11), stigmasterol (12), and β-sitosterol (13). The identity of these compounds was confirmed by comparison with published data as well as co-TLC with authentic samples. Journal of Bangladesh Academy of Sciences, Vol. 44, No. 2, 85-93, 2020
41

Atun, Sri, Nurfina Aznama, Retno Arianingrum i Masatake Niwab. "STRUCTURE IDENTIFICATION OF A TRIMER STILBENOID COMPOUND FROM STEM BARK Hopea nigra (DIPTEROCARPACEAE)". Indonesian Journal of Chemistry 5, nr 3 (15.06.2010): 211–14. http://dx.doi.org/10.22146/ijc.21791.

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Bioactivity as antihephatotoxic directed fractionation of aceton extract from the stem bark of Hopea nigra (Dipterocarpaceae) afforded a stilbenoid trimer, namely vaticanol G (1). The structure of this compound were elucidated based on physical and spectroscopic data (UV, IR, MS, 1H and 13C NMR 1D and 2D). Keywords: Vaticanol G; Hopea nigra; antihepatotoxic; Dipterocarpaceae.
42

Siivari, Jari, Arto Maaninen, Esa Haapaniemi, Risto S. Laitinen i Tristram Chivers. "Formation and Identification of Bis[bis(trimethylsilyl)amino]triand tetrachalcogenides". Zeitschrift für Naturforschung B 50, nr 11 (1.11.1995): 1575–82. http://dx.doi.org/10.1515/znb-1995-1101.

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The reaction of (Me3Si)2NLi with SCl2 and elemental sulfur or with Se2Cl2 and elemental selenium leads to the formation of mixtures of bis[bis(trimethylsilyl)amino]suIfides and selenides [(Me3Si)2N]2Ex (E = S or Se; x = 1 - 4 ). The reaction products were identified by mass spectroscopy as well as by 77Se and 13C NMR spectroscopy. The reaction of (Me3Si)2NH with S2Cl2 produces [(Me3Si)2N]2S3 as the main product with only traces of other aminosulfides. [(Me3Si)2N]2S3 was purified by distillation under reduced pressure and identified by elem ental analysis, mass spectroscopy, and by 1H, 13C, and 14N NMR spectroscopy. The successful cyclocondensation reaction of [(Me3Si)2N]2S3 with SCl2 and SO2Cl2 produces S4N2 in 72% yield and provides further verification of the identity of bis[bis(trimethylsilyl)amino]trisulfide. While the analogous reaction of (Me3Si)2NH with Se2Cl2 also leads to the formation of [(Me3Si)2N]2Se3 (48 mol %) as the main product, the reaction mixture contains [(Me3Si)2N]2Se2 and [(Me3Si)2N]2Se4 in significant amounts (17 and 35 mol %, respectively). Attempts to purify the mixture by distillation under reduced pressure resulted only in the formation of a 83:17 mixture of [(Me3Si)2N]2Se2 and [(Me3Si)2N]2Se3.
43

Di Pietro, Maria Enrica, Alberto Mannu i Andrea Mele. "NMR Determination of Free Fatty Acids in Vegetable Oils". Processes 8, nr 4 (31.03.2020): 410. http://dx.doi.org/10.3390/pr8040410.

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The identification and quantification of free fatty acids (FFA) in edible and non-edible vegetable oils, including waste cooking oils, is a crucial index to assess their quality and drives their use in different application fields. NMR spectroscopy represents an alternative tool to conventional methods for the determination of FFA content, providing us with interesting advantages. Here the approaches reported in the literature based on 1H, 13C and 31P NMR are illustrated and compared, highlighting the pros and cons of the suggested strategies.
44

Bakibaev, А. А., М. Zh Sadvakassova, V. S. Malkov, R. Sh Еrkasov, A. A. Sorvanov i O. A. Kotelnikov. "Study of the biologically active acyclic ureas by nuclear magnetic resonance". Bulletin of the Karaganda University. "Chemistry" series 100, nr 4 (30.12.2020): 60–74. http://dx.doi.org/10.31489/2020ch4/60-74.

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A wide variety of acyclic ureas comprising alkyl, arylalkyl, acyl, and aryl functional groups are investigated by nuclear magnetic resonance spectroscopy. In general, spectral characteristics of more than 130 substances based on acyclic ureas dissolved in deuterated dimethyl sulfoxide at room temperature are studied. The re-sults obtained based on the studies of 1H and 13C NMR spectra of urea and its N-alkyl-, N-arylalkyl-, N-aryl- and 1,3-diaryl derivatives are presented, and the effect of these functional groups on the chemical shifts in carbonyl and amide moieties in acyclic urea derivatives is discussed. An introduction of any type of substitu-ent (electron-withdrawing or electron-donating) into urea molecule is stated to result in a strong upfield shift in 13C NMR spectra relatively to unsubstituted urea. A strong sensitivity of NH protons to the presence of acyl and aryl groups in nuclear magnetic resonance spectra is pointed out. In some cases, qualitative depend-encies between the chemical shifts in the NMR spectra and the structure of the studied acyclic ureas are re-vealed. A summary of the results on chemical shifts in the NMR spectra of the investigated substances allows determining the ranges of chemical shift variations of the key protons and carbon atoms in acyclic ureas. The literature describing the synthesis procedures are provided. The results obtained significantly expand the methods of reliable identification of biologically active acyclic ureas and their metabolites that makes it promising to use NMR spectroscopy both in biochemistry and in clinical practice.
45

Ferreira, Marcelo J. P., Francimeiry C. Oliveira, Sandra A. V. Alvarenga, Patrı́cia A. T. Macari, Gilberto V. Rodrigues i Vicente P. Emerenciano. "Automatic identification by 13C NMR of substituent groups bonded in natural product skeletons". Computers & Chemistry 26, nr 6 (listopad 2002): 601–32. http://dx.doi.org/10.1016/s0097-8485(02)00029-3.

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46

Moore, Jeremy K., J. Andrew Surface, Allison Brenner, Philip Skemer, Mark S. Conradi i Sophia E. Hayes. "Quantitative Identification of Metastable Magnesium Carbonate Minerals by Solid-State 13C NMR Spectroscopy". Environmental Science & Technology 49, nr 1 (17.12.2014): 657–64. http://dx.doi.org/10.1021/es503390d.

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Nam, Anne-Marie, Mathieu Paoli, Vincent Castola, Joseph Casanova i Ange Bighelli. "Identification and Quantitative Determination of Lignans in Cedrus atlantica Resins using 13C NMR Spectroscopy". Natural Product Communications 6, nr 3 (marzec 2011): 1934578X1100600. http://dx.doi.org/10.1177/1934578x1100600316.

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Identification and quantitative determination of individual components of resin collected on the trunk of 28 Cedrus atlantica trees, grown in Corsica, has been carried out using 13C NMR spectroscopy. Eight resin acids bearing either the pimarane or abietane skeleton, two monoterpene hydrocarbons and four oxygenated neutral diterpenes have been identified, as well as three lignans, scarcely found in resins. Three groups could be distinguished within the 28 resin samples. The nine samples of Group I had their composition dominated by diterpene acids (33.7-45.8%), with abietic acid (6.2-18.7%) and isopimaric acid (5.1-12.6%) being the major components. The four samples of Group II contained resin acids (main components) and lignans in moderate amounts (up to 10.3%). Conversely, lignans (38.8-63.8%) were by far the major components of the 15 samples of Group III. Depending on the sample, the major component was pinoresinol (18.1-38.9%), lariciresinol (17.2-33.7%) or lariciresinol 9′-acetate (16.9-29.1%). Finally, due to the high biological interest in lignans, a rapid procedure, based on 1H NMR spectroscopy, was developed for quantification of lignans in resins of C. atlantica.
48

Kazalaki, Aristea, Maria Misiak, Apostolos Spyros i Photis Dais. "Identification and quantitative determination of carbohydrate molecules in Greek honey by employing 13C NMR spectroscopy". Analytical Methods 7, nr 14 (2015): 5962–72. http://dx.doi.org/10.1039/c5ay01243k.

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Irmawan, Muhammad, Frederyk Mandey i Seniwati Dali. "Isolasi, Identifikasi, Karakterisasi Dan Uji Toksisitas Senyawa Metabolit Sekunder Fraksi Nonpolar Akar Babandotan (Ageratum conyzoides L)". Indo. J. Chem. Res. 6, nr 1 (31.07.2018): 1–5. http://dx.doi.org/10.30598//ijcr.2018.6-muh.

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Ageratum Conyzoides L. has a toxic and bioactive component as anti-cancer and especially for the root, it has anti-tumor. In order to figure out the active component, it is necessary to do four steps; isolation, identification, characterization, and toxicity essay Brine Shrimp Lethality Test (BSLT) of non-polar fraction Ageratum conyzoides L plant. Isolation method consist of four parts; extraction, partitioning of Kupchan method, fractionation, and purification. Fractionation method uses press column chromatography (KTT). Furthermore, purification process uses thin layer chromatography (TLC) and characterization with spectroscopy FTIR, 1H-NMR and 13C-NMR. Then characterization utilizes spectroscopy FTIR, 1H-NMR and 13C-NMR. The toxicity essay toward Artemia Salina Leach n-hexane fraction and dichloromethane fraction showed that the fraction had toxic properties with number of LC50 are 0,0237 and 4,642 µg/mL respectively. Moreover, n-hexane fraction has succeed in isolating Stigmasterol compound shaped white crystalline needles with 19.6 mg weight, 143-144 °C melting point and and had toxic properties with number of LC50 are 30,33 µg/mL.
50

BISHOP, G. Reid, Zhenyu ZHU, L. Tracy WHITEHEAD, P. Rickey HICKS i L. Victor DAVIDSON. "Identification of reaction products and intermediates of aromatic-amine dehydrogenase by 15N and 13C NMR". Biochemical Journal 330, nr 3 (15.03.1998): 1159–63. http://dx.doi.org/10.1042/bj3301159.

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13C- and 15N-NMR studies of the reaction of aromatic amine dehydrogenase (AADH) with methylamine demonstrated that the products of the reductive half-reaction are an equivalent of formaldehyde hydrate and a reduced aminoquinol form of the tryptophan tryptophylquinone (TTQ) cofactor which contains covalently bound substrate-derived N. These data are consistent with the Ping Pong kinetic mechanism and aminotransferase-type chemical reaction mechanism which have been previously proposed for AADH. Comparison of the 15N-NMR spectra of the aminoquinol TTQ intermediates of AADH and methylamine dehydrogenase (MADH) revealed that the substrate-derived aminoquinol N of AADH and MADH exhibited distinct 15N chemical shifts which are separated by approx. 7 p.p.m. In each case, the signal for the substrate-derived aminoquinol N appears optimally with short pulse delay and exhibits a relaxation time and chemical shift which are consistent with 15N covalently bound to an aromatic ring (i.e. aminoquinol) which is attached to a rigid protein matrix. The aminoquinol of AADH is less stable against reoxidation than that of MADH. These data suggest that differences in the active-site mediated electrostatic environments of the aminoquinol N in the respective enzymes may influence both the observed 15N chemical shift and the relative reactivities of the TTQ aminoquinols towards oxygen. These data also demonstrate the utility of 13C- and 15N-NMR spectroscopy as a tool for monitoring the intermediates and products of enzyme-catalysed transformations.

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