Chemical constituents from Glehnia littoralis and their chemotaxonomic significance

Abstract

Phytochemical investigation of the roots of Glehnia littoralis Fr. Schmidt. ex Miq. led to the isolation of 16 known compounds, including three β-carboline alkaloids (1–3), four phenylpropanoids (4–7), five phenolic acids (8–12), three polyacetylenes (13–15) and one fatty acid (16). The structures of these compounds were elucidated on the basis of spectral analysis and comparison with those reported in literatures. To the best of knowledge, the report of the first β-carboline alkaloid in the Umbelliferae family. Additionally, compounds 1–5, 9, 10 and 16 have not been reported from any species in Umbelliferae family, compounds 7, 8 and 12 were isolated from the genus Glehnia for the first time and could be of the chemotaxinomic significance and serve as valuable chemotaxonomic makers for G. littoralis. The chemotaxonomic significance of the isolated compounds was summarised.     

Chemical structure of composites derived from poly(silicic acid) and 2‐hydroxyethylmethacrylate

Organic–inorganic hybrids from 2‐hydroxyethylmethacrylate (HEMA) and poly(silicic acid)s were prepared and characterized. The molecular architecture of the inorganic phase was studied with ²⁹Si NMR spectroscopy, and the effect of acid concentration and reaction time on the properties of poly(silicic acid) were elucidated. Interactions between phases were studied with NMR spectroscopy and gel permeation chromatography, and the coexistence and connectivity of the two phases were investigated. Contrary to previous assumptions, evidence was found that indicated that the organic and inorganic phases of this class of sol–gel materials were not covalently linked. The curing process was studied by infrared spectroscopy, by which the disappearance of terminal double bonds of HEMA monomer were monitored. Thermogravimetric analysis profiles showed that the inorganic phase content was about 10 wt %, and it was varied slightly by changes in the molar ratio of the components. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1342–1352, 2001     

Chemical constituents isolated from stems of Schisandra chinensis and their antifeedant activity against Tribolium castaneum

Abstract

One new sesquiterpene (α-iso-cubebenol acetate, 8), together with 9 known compounds (1-7, 9, 10) were isolated from the stems of Schisandra chinensis (Turcz.) Baill. by repeated silica gel column chromatography. Based on the results of MS, NMR spectra and comparing with literature data, the six dibenzocyclooctadiene lignans were identified as schizandrin A to C (1-3), schizandrin (4), schisantherin A (5) and gomisin J (6), the two sesquiterpenes were identified as α-iso-cubebenol (7) and α-iso-cubebenol acetate (8), while the two triterpenic acids were identified as ganwuweizic acid (9) and kadsuric acid (10). The antifeedant activity of the 10 compounds against Tribolium castaneum adults was tested. Gomisin J (6) exhibited activity at 1500?ppm concentration with 40.3% antifeeding index percentages. As for the dibenzocyclooctene lignans (compounds 1–3, 6), the number of methylenedioxies and the position of hydroxyl groups were the main factors to affect their antifeedant activities.     

Atomic Contributions from Spin‐Orbit Coupling to 29Si NMR Chemical Shifts in Metallasilatrane Complexes

New members of a novel class of metallasilatrane complexes [X‐Si‐(μ‐mt)₄‐M‐Y], with M=Ni, Pd, Pt, X=F, Cl, Y=Cl, Br, I, and mt=2‐mercapto‐1‐methylimidazolide, have been synthesized and characterized structurally by X‐ray diffraction and by ²⁹Si solid‐state NMR. Spin‐orbit (SO) effects on the ²⁹Si chemical shifts induced by the metal, by the sulfur atoms in the ligand, and by heavy halide ligands Y=Cl, Br, I were investigated with the help of relativistic density functional calculations. Operators used in the calculations were constructed such that SO coupling can selectively be switched off for certain atoms. The unexpectedly large SO effects on the ²⁹Si shielding in the Ni complex with X=Y=Cl reported recently originate directly from the Ni atom, not from other moderately heavy atoms in the complex. With respect to Pd, SO effects are amplified for Ni owing to its smaller ligand‐field splitting, despite the smaller nuclear charge. In the X=Cl, Y=Cl, Br, I series of complexes the Y ligand strongly modulates the ²⁹Si shift by amplifying or suppressing the metal SO effects. The pronounced delocalization of the partially covalent M←Y bond plays an important role in modulating the ²⁹Si shielding. We also demonstrate an influence from the X ligand on the ²⁹Si SO shielding contributions originating at Y. The NMR spectra for [X‐Si‐(μ‐mt)₄‐M‐Y] must be interpreted mainly based on electronic and relativistic effects, rather than structural differences between the complexes. The results highlight the sometimes unintuitive role of SO coupling in NMR spectra of complexes containing heavy atoms.     

Chemical constituents from leaves and trunk bark of Rinorea oblongifolia (Violaceae)

Abstract

Two new coruleoellagic acid derivatives, 3,4′,5,5′,-tetramethylcoruleoellagic acid (1); 3′,4,4′,5,5′-pentamethylcoruleoellagic acid (2) and a new friedelane-type triterpene derivative rinol (5), were isolated from leaves and trunk bark of Rinorea oblongifolia (Violaceae) along with seven known compounds including 3,3′,4,4′,5′-pentamethylcoruleoellagic acid (3), hexamethylcoruleoellagic acid (4), 28-hydroxyfriedelin (6), friedelin (7), friedelan-3-ol (8), scopoletin (9) and β-sitosterol-3-O-β-D-glucopyranoside (10). Their structures were elucidated by means of spectroscopic methods including IR, 1D and 2D NMR in conjunction with mass spectrometry. Crude extracts of leaves and trunk bark as well as compounds 1–4 were evaluated for their antibacterial activities against 7 pathogenic bacterial strains (Streptococcus pneumoniae ATCC49619, Staphylococcus aureus ATCC 43300, Klepsiella pneumoniae ATCC 700603, Haemophilus influenza ATCC 49247, Escherichia coli ATCC 25922, Pseudomonas aeruginosa HM601, Staphylococcus aureus BAA 977). Compound (3) displayed noteworthy activity against Haemophilus influenza with MIC value of 9.38?µg/mL.     

Rapid Determination of Fast Protein Dynamics from NMR Chemical Exchange Saturation Transfer Data

Functional motions of ¹⁵N‐labeled proteins can be monitored by solution NMR spin relaxation experiments over a broad range of timescales. These experiments however typically take of the order of several days to a week per protein. Recently, NMR chemical exchange saturation transfer (CEST) experiments have emerged to probe slow millisecond motions complementing R_1ρ and CPMG‐type experiments. CEST also simultaneously reports on site‐specific R₁ and R₂ parameters. It is shown here how CEST‐derived R₁ and R₂ relaxation parameters can be measured within a few hours at an accuracy comparable to traditional relaxation experiments. Using a “lean” version of the model‐free approach S² order parameters can be determined that match those from the standard model‐free approach applied to ¹⁵N R₁, R₂, and {¹H}‐¹⁵N NOE data. The new methodology, which is demonstrated for ubiquitin and arginine kinase (42 kDa), should serve as an effective screening tool of protein dynamics from picosecond‐to‐millisecond timescales.     

Structural determination of two new triterpenoids from Potentilla discolor Bunge by NMR techniques

Two new pentacyclic triterpenoids, 3alpha, 30-dihydroxylup-20(29)-en-27-oic acid (1) and (20S)-3alpha, 29-dihydroxylupan-27-oic acid (2) were isolated from the whole herbs of Potentilla discolor Bunge. The structures of these two new compounds were elucidated, and complete assignments of the (1)H and (13)C NMR spectroscopic data were achieved by 1D and 2D NMR experiments (HSQC, HMBC, (1)H-(1)HCOSY and ROESY).     

Structure of teichoic acid from the marine proteobacterium <Emphasis Type="Italic">Sulfitobacter brevis</Emphasis> KMM 6006

A glycopolymer was isolated from the marine gram-negative bacterium Sulfitobacter brevis strain KMM 6006 and found to be teichoic acid containing ribitol, glycerine, and N-acetyl-D-glucosamine. The polymeric chain consisted of alternating 1,5-poly(4-N-acetyl-β-D-glucosaminylribitophosphate) and 1,3-poly(glycerophosphate) based on ¹³C and ³¹P NMR spectroscopy of the native polymer and the glycoside obtained by its dephosphorylation. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 533–536, November–December, 2007.     

Preparation of Highly Functionalised Benzofurans from ortho‐Hydroxyphenones and Dichloroethylene: Applications and Mechanistic Investigations

Highly functionalised benzofurans have been prepared from ortho‐hydroxyphenones and 1,1‐dichloroethylene. The key intermediate, a chloromethylene furan, smoothly rearranged into the corresponding benzofuran carbaldehyde under acidic conditions. Some mechanistic investigations have been performed and several biologically active benzofurans have been synthesised.     

Moringa oleifera leaves from Brazil: Influence of seasonality,regrowth age and,region in biochemical markers and antioxidant potential

Moringa oleifera leaves are cultivated in warm regions of Brazil for commercial ends due to their nutritional and biological properties. This study evaluated, by chemometric tools, the influence of seasonality (winter, spring, autumn, and summer), growing area in Brazil (South, Southeast, and Northeast), and regrowth age (40 and 80 days) in antioxidant potential, and biochemical markers determined by HPLC-DAD. The results obtained in the present study showed that all the parameters evaluated were affected by seasonality, regrowth age, and growing region. The content of phenolic compounds and antioxidant activity using the ABTS method was higher in samples cultivated in the southeast (59.4 mg GAE g^?1 and 346 µmol TEAC g^?1, respectively). The highest antioxidant activities evaluated by DPPH and FRAP methods were obtained from leaves of the southeast and northeast. In addition, young leaves presented higher antioxidant potential and total phenolic content. The cultivation region significantly influenced the content of chlorogenic acid, isoquercitrin, and astragalin, which ranged from 4.2 to 7.2 mg g^?1, 8.0 to 10.7 mg g^?1, and 2.2 to 3.8 mg g^?1, respectively. In addition, a positive correlation between solar radiation and temperature with caffeic acid, rutin, phenolic compounds, and antioxidant assay from the DPPH method was observed. Additionally, the RGB pattern of the images of these leaves was correlated with the levels of compounds with antioxidant activity. Models generated through machine learning showed good performances, and ABTS and rutin analyses developed the best models with a coefficient of determination above 75 %. Thus, color patterns can be used to measure the antioxidant activity by the ABTS method and to determine the rutin concentration in M. oleifera leaves.     

A new chromanone acid from the stem bark of Calophyllum teysmannii

A new chromanone acid, namely caloteysmannic acid (1), along with three known compounds, calolongic acid (2), isocalolongic acid (3) and stigmasterol (4) were isolated from the stem bark of Calophyllum teysmannii. All these compounds were evaluated for their cytotoxic and antioxidant activities in the MTT and DPPH assays, respectively. The structure of compound 1 was determined by means of spectroscopic methods including 1D and 2D NMR experiments as well as HR-EIMS spectrometry. The stereochemical assignment of compound 1 was done based on the NMR results and X-ray crystallographic analysis. The preliminary assay results revealed that all the test compounds displayed potent inhibitory activity against HeLa cancer cell line, in particular with compound 1 which exhibited the highest cytotoxic activity comparable to the positive control used, cisplatin. However, no significant antioxidant activity was observed for all the test compounds in the DPPH radical scavenging capacity assay.     

Polymorphism in crystalline cinchomeronic acid

The structural relationship between the two crystal forms of cinchomeronic acid (CA 3,4-dicarboxypyridine) has been investigated by single crystal X-ray diffraction, IR and Raman spectroscopy and solid state NMR spectroscopy, showing that the two polymorphs form a monotropic system, with the orthorhombic form I being the thermodynamically stable form, while the monoclinic form II is unstable. In both forms CA crystallizes as a zwitterion and decomposes before melting. The crystal structure and spectroscopic analysis indicate that the difference in stability can be ascribed to the strength of the hydrogen-bonding patterns established by the protonated N-atom and the carboxylic/carboxylate O-atoms.     

Spectroscopic study of the water-soluble organic matter isolated from atmospheric aerosols collected under different atmospheric conditions

The composition of the water-soluble organic matter from fine aerosols collected in a rural location during two different meteorological conditions (summer and autumn) was investigated by UV-vis, synchronous fluorescence (with Δλ = 20 nm), FT-IR and CPMAS-¹³C NMR spectroscopies. A seasonal variation in the concentration of total carbon, organic carbon and water-soluble organic carbon was confirmed, with higher values during the autumn and lower values during the summer season. The chemical characterisation of the water-soluble organic matter showed that both samples are dominated by a high content of aliphatic structures, carboxyl groups and aliphatic carbons single bonded to one oxygen or nitrogen atom. However, the autumn sample exhibits a higher aromatic content than the summer sample, plus signals due to carbons of phenol, ketones and methoxyl groups. These signals were attributed to lignin breakdown products which are likely to be released during wood combustion processes. The obtained results put into evidence the major contribution of biomass burning processes in domestic fireplaces during low temperature conditions into both the concentration and the bulk chemical properties of the WSOC from fine aerosols.     

茶叶化学成分指纹识别中样品制备方法的优化

根据指纹识别实验对样品的要求, 以¹H NMR和主成分分析(PCA)为测试与评估手段, 对茶叶中化学成分提取条件的优化方法进行了研究. 针对生物指纹识别实验中样本体系复杂及化学组分含量多等特点, 利用主成分分析对检测样品质控的多因素进行综合分析, 最终确立了茶叶中化学成分提取制备的实验条件. 利用所建立的样品制备程序对4种茶叶进行预处理和测试, 结果表明, 所建立的方法稳定、可靠, 可以满足茶叶代谢物¹H NMR指纹识别研究的要求. 本文所提出的优化方法简单可靠, 可用于复杂样本体系标准样品预处理方法的建立.     

Chemical Reaction Monitoring using Zero-Field Nuclear Magnetic Resonance Enables Study of Heterogeneous Samples in Metal Containers

We demonstrate that heterogeneous/biphasic chemical reactions can be monitored with high spectroscopic resolution using zero-field nuclear magnetic resonance spectroscopy. This is possible because magnetic susceptibility broadening is negligible at ultralow magnetic fields. We show the two-step hydrogenation of dimethyl acetylenedicarboxylate with para-enriched hydrogen gas in conventional glass NMR tubes, as well as in a titanium tube. The low frequency zero-field NMR signals ensure that there is no significant signal attenuation arising from shielding by the electrically conductive sample container. This method paves the way for in situ monitoring of reactions in complex heterogeneous multiphase systems and in reactors made of conductive materials while maintaining resolution and chemical specificity.     

A Journey from Thermally Tunable Synthesis to Spectroscopy of Phenylmethanimine in Gas Phase and Solution

Phenylmethanimine is an aromatic imine with a twofold relevance in chemistry: organic synthesis and astrochemistry. To tackle both aspects, a multidisciplinary strategy has been exploited and a new, easily accessible synthetic approach to generate stable imine-intermediates in the gas phase and in solution has been introduced. The combination of this formation pathway, based on the thermal decomposition of hydrobenzamide, with a state-of-the-art computational characterization of phenylmethanimine laid the foundation for its first laboratory observation by means of rotational electric resonance spectroscopy. Both E and Z isomers have been accurately characterized, thus providing a reliable basis to guide future astronomical observations. A further characterization has been carried out by nuclear magnetic resonance spectroscopy, showing the feasibility of this synthetic approach in solution. The temperature dependence as well as possible mechanisms of the thermolysis process have been examined.