[Studies on the chemical constituents of Schisandra pubescens]

OBJECTIVE

To study the chemical constituents of Schisandra pubescens.

METHODS

The chemical constituents were isolated by silica gel, Prep-HPLC and Prep-TLC methods. And their structures were elucidated by physical-chemical and spectroscopic methods.

RESULTS

Seven compounds were obtained and identified as (+)-gomisin K2 (I), gomisin S (II), Pregomisin (III), Schisantherin A (IV), Schicantherin B (V), Angeloylgomisin Q (VI), Rubrildilactione (VII).

CONCLUSION

All compounds are isolated from this plant for the first time.

1H NMR titration and quantum calculation for the inclusion complexes of cis-cyclooctene, cis, cis-1, 3-cyclooctadiene and cis, cis-1, 5-cyclooctadiene with beta-cyclodextrin

The inclusion behavior of cis-cyclooctene, cis, cis-1, 3-cyclooctadiene and cis, cis-1, 5-cyclooctadiene with beta-cyclodextrin (beta-CD) was studied by using (1)H NMR method in D(2)O/CD(3)OD solution and PM3 quantum-chemical simulation in vacuum. The experimental results indicate that each guest molecule penetrates deeply into beta-CD cavity and forms equimolecular inclusion complex with the host. The association constants of the complexes were determined by non-linear least-square method on the bases of the conversion-dependent chemical shift of two protons of the host molecule. The inclusion process and the most probable structure of the inclusion complexes were simulated using PM3 energy scanning and optimization. The trend of stability of the three inclusion complexes deduced from their calculated stabilization energies agrees well with the order of their association constants obtained from NMR experiments.

[Study on the chemical constituents of the fruit handles from Schizandra chinensis]

OBJECTIVE

To study the chemical constituents of the fruit handles from Schizandra chinensis.

METHODS

Compounds from the 85% ethanol extracts were isolated by silica gel, Sephadex LH-20, recrystal, etc., and their structures were identified by the spectral analysis and chemical evidence.

RESULTS

Eight compounds were isolated and identified as wuweizisu C (I), ganwuweizic acid(II), beta-sitosterol(III), gomisin A(IV), schizandrin(V), daucosterol(VI), wuweizisu A(VII), gamma-schizandrin (VIII).

CONCLUSION

Compounds I - VIII are isolated from the fruit handles of Schizandra chinensis for the first time.

Complete assignments of 1H and 13C NMR data for new dibenzocyclooctadiene lignans from Kadsura oblongifolia

Two new dibenzocyclooctadiene lignans, named kadoblongifolins A (1) and B (2), and one new natural product dibenzocyclooctadiene lignan, named kadoblongifolin C (3), were isolated from the stems of Kadsura oblongifolia (K. oblongifolia), together with five known ones, schizanrin F (4), propinquanin C (5), schisantherin G (6), heteroclitin Q (7), kadsurarin (8). The structures of these new lignans were elucidated by a combination of high-resolution electron ionization mass spectrometry (HR-EI-MS), (1)H NMR, (13)C NMR, HMQC, HMBC, and NOESY spectra.

Characterisation and identification of isomeric dibenzocyclooctadiene lignans from Schisandra Chinensis by high-performance liquid chromatography combined with electrospray ionisation tandem mass spectrometry

INTRODUCTION

Dibenzocyclooctadiene lignans are bioactive constituents in Schisandra chinensis (Turcz.) Baill. They are often present as isomers and this makes structural discrimination difficult.

OBJECTIVE

To develop a rapid approach towards the characterisation and identification of isomeric dibenzocyclooctadiene lignans from S. chinensis using HPLC-PAD-ESI-MS(n).

METHODOLOGY

The fragmentation behaviours of seven dibenzocyclooctadiene lignans from S. chinensis were studied using ion trap mass spectrometry with positive electrospray ionisation and loop injection. The fragmentation patterns of angeloylgomisin H, tigloylgomisin H, benzoylgomisin H and gomisin D were supported by high-resolution mass spectrometric analysis of some characteristic ions using a time-of-flight mass spectrometer. Combined with high-performance liquid chromatography and photodiode array detection, the established approach to the structural identification of dibenzocyclooctadiene lignans by ion trap mass spectrometry was applied to the analysis of extracts of S. chinensis.

RESULTS

According to the HPLC retention behaviour, the diagnostic UV spectra and the molecular structural information provided by multistage mass spectrometry spectra and the literature, a total of 25 dibenzocyclooctadiene lignans, including seven groups of lignan isomers, were identified or tentatively characterised in S. chinensis rapidly. One of these was reported as a constituent of S. chinensis for the first time.

CONCLUSION

This study has shown that HPLC-PAD-ESI-MS(n) may be used as an effective and rapid method for the characterisation and identification of isomeric dibenzocyclooctadiene lignans from S. chinensis.

Structural characterization and thermal stabilities of the isomers of the brominated flame retardant 1,2,5,6-tetrabromocyclooctane (TBCO)

1,2,5,6-Tetrabromocyclooctane (TBCO) is a commercial brominated flame retardant that is employed mainly as an additive in textiles, paints and plastics. Very little is known about its presence or behavior in the environment or its analysis. TBCO can exist as two diastereomers, the stereochemistries of which have not been previously reported. We have named the first eluting isomer, under HPLC conditions, as alpha-TBCO (alpha-TBCO) and the later eluting isomer as beta-TBCO (beta-TBCO) when using an Acquity UPLC BEH C(18) column with methanol/acetonitrile/water as the mobile phase. The structural elucidation of these two isomers was accomplished by 1H NMR spectroscopy, GC/MS, LC/MS and X-ray structure determinations. alpha-TBCO is (1R,2R,5S,6S)-1,2,5,6-tetrabromocyclooctane and beta-TBCO is rac-(1R,2R,5R,6R)-1,2,5,6-tetrabromocyclooctane. As with some other brominated cycloaliphatic compounds, TBCO is thermally labile and the isomers easily interconvert. A thermal equilibrium mixture of alpha- and beta-TBCO consists of approximately 15% and 85% of these isomers, respectively. Separation of the two diastereomers, with minimal thermal interconversion between them, is achievable by careful selection of GC-capillary column length and injector temperature. LC/MS analyses of TBCO also presents an analytical challenge due to poor resolution of the isomers on chromatographic stationary phases, and weak intensity of molecular ions (or major fragment ions) when using LC-ESI/MS. Only bromide ions were seen in the mass spectra. APCI and APPI also failed to produce the molecular ion with sufficient intensity for identification.

Ring-expansion metathesis polymerization: catalyst-dependent polymerization profiles

Ring-expansion metathesis polymerization (REMP) mediated by recently developed cyclic Ru catalysts has been studied in detail with a focus on the polymer products obtained under varied reaction conditions and catalyst architectures. Depending upon the nature of the catalyst structure, two distinct molecular weight evolutions were observed. Polymerization conducted with catalysts bearing six-carbon tethers displayed rapid polymer molecular weight growth which reached a maximum value at ca. 70% monomer conversion, resembling a chain-growth polymerization mechanism. In contrast, five-carbon-tethered catalysts led to molecular weight growth that resembled a step-growth mechanism with a steep increase occurring only after 95% monomer conversion. The underlying reason for these mechanistic differences appeared to be ready release of five-carbon-tethered catalysts from growing polymer rings, which competed significantly with propagation. Owing to reversible chain transfer and the lack of end groups in REMP, the final molecular weights of cyclic polymers was controlled by thermodynamic equilibria. Large ring sizes in the range of 60-120 kDa were observed at equilibrium for polycyclooctene and polycyclododecatriene, which were found to be independent of catalyst structure and initial monomer/catalyst ratio. While six-carbon-tethered catalysts were slowly incorporated into the formed cyclic polymer, the incorporation of five-carbon-tethered catalysts was minimal, as revealed by ICP-MS. Further polymer analysis was conducted using melt-state magic-angle spinning (13)C NMR spectroscopy of both linear and cyclic polymers, which revealed little or no chain ends for the latter topology.

Spectroscopic, quantum chemical DFT/HF study and synthesis of [2.2.1] hept-2'-en-2'-amino-N-azatricyclo [3.2.1.0(2,4)] octane

The compound 4-N-bicyclo [2.2.1] hept-2'-en-2'-amino-N-azatricyclo [3.2.1.0(2,4)] octane (2) has been synthesized and characterized by elemental analysis, IR, UV-vis, mass and NMR. Density functional theory (DFT) and Hartree-Fock (HF) calculations have been carried out for the title compound by using the standard 6-31G* basis set. The calculated results show that the predicted geometry can well reproduce the structural parameters. Predicted vibrational frequencies have been assigned and compared with experimental IR spectra and they complement each other. The theoretical electronic absorption spectra have been calculated by using CIS, TD-DFT and ZINDO methods. The (13)C NMR and (1)H NMR of compound (2) have been calculated by means of Becke 3-Lee-Yang-Parr (B3LYP) density functional method with 6-31G* basis set. Comparison between the experimental and the theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting NMR properties. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated.

Nortriterpenoids and lignans from Schisandra sphenanthera

Nortriterpenoids, sphenadilactone C (1) and sphenasin A (2), together with four known lignans (3-6), were isolated from the leaves and stems of Schisandra sphenanthera. Their structures were elucidated by extensive analysis of 1D and 2D NMR spectroscopic data and compound 2 was further confirmed by single-crystal X-ray diffraction. Compound 1 features a partial enol moiety and an acetamide group in its structure. In addition, compounds 1, 3-6 showed weak anti-HIV-1 activity with EC(50) values in the range of 15.5-29.5 microg/mL.

Nordihydroguaiaretic acid autoxidation produces a schisandrin-like dibenzocyclooctadiene lignan

The lignan meso-nordihydroguaiaretic acid is known to undergo spontaneous oxidation in alkaline solution. In the presence of the trapping agent glutathione, the major oxidation products are consistent with the formation of a meso-nordihydroguaiaretic acid ortho-quinone. In the absence of a trapping agent however, the major oxidation product of meso-nordihydroguaiaretic acid in aqueous solution is a unique, stable schisandrin-like dibenzocyclooctadiene lignan that may be responsible for some of the biological effects of nordihydroguaiaretic acid.

Algorithmic dimensionality reduction for molecular structure analysis

Dimensionality reduction approaches have been used to exploit the redundancy in a Cartesian coordinate representation of molecular motion by producing low-dimensional representations of molecular motion. This has been used to help visualize complex energy landscapes, to extend the time scales of simulation, and to improve the efficiency of optimization. Until recently, linear approaches for dimensionality reduction have been employed. Here, we investigate the efficacy of several automated algorithms for nonlinear dimensionality reduction for representation of trans, trans-1,2,4-trifluorocyclo-octane conformation--a molecule whose structure can be described on a 2-manifold in a Cartesian coordinate phase space. We describe an efficient approach for a deterministic enumeration of ring conformations. We demonstrate a drastic improvement in dimensionality reduction with the use of nonlinear methods. We discuss the use of dimensionality reduction algorithms for estimating intrinsic dimensionality and the relationship to the Whitney embedding theorem. Additionally, we investigate the influence of the choice of high-dimensional encoding on the reduction. We show for the case studied that, in terms of reconstruction error root mean square deviation, Cartesian coordinate representations and encodings based on interatom distances provide better performance than encodings based on a dihedral angle representation.

Schisanhenol attenuated ox-LDL-induced apoptosis and reactive oxygen species generation in bovine aorta endothelial cells in vitro

The aim of this paper was to investigate the protective effect of schisanhenol (Sal) isolated from Schisandra rubriflora Rhed, on human ox-LDL-induced bovine aorta endothelial cells (BAECs) apoptosis and intracellular reactive oxygen species (ROS) production in vitro. The BAECs were cultured with ox-LDL (200 microg/ml) in the presence and absence of Sal (10 and 50 micromol L(- 1)) for 24 h. The cytotoxicity of ox-LDL was evaluated by LDH leakage, cell viability and morphological change. Cell apoptosis was estimated by DNA ladder, chromatin condensation, and flow cytometry assay. The intracellular ROS production was detected by using DCF, a ROS probe, with laser confocal microscopy and flow cytometry. Sal was shown to reduce LDH leakage and increase cell viability. Sal also attenuated ox-LDL-induced BAECs apoptosis as indicated in typical internucleosomal DNA degradation (DNA ladder), condensed chromatin, and the sub-G1 peak appearance in flow cytometry assay. Furthermore, Sal was shown to inhibit ROS generation in BAECs with stimulation of ox-LDL. The results indicated that the anti-apoptosis effect of Sal on BACSs might be related to its inhibition of ROS generation.

Schizandrin reverses memory impairment in rats

The present study investigated the effect of schizandrin, a component of the fruit of Schizandra chinesis Baill (Fructus Schizandrae), on memory impairment in rats. Scopolamine (0.5 mg/kg, i.p.), a non-selective muscarinic receptor antagonist, markedly impaired spatial memory in an eight-arm radial maze. A higher dose of scopolamine (3 mg/kg, i.p.) also impaired the passive avoidance response. Schizandrin (1 and 10 mg/kg, p.o.) significantly reversed the scopolamine-induced impairment of spatial memory. Similarly, schizandrin (1 mg/kg, p.o.) significantly reversed the scopolamine-induced impairment of the passive avoidance response. Moreover, in mice, schizandrin (1 and 10 mg/kg, p.o.) enhanced tremors induced by oxotremorine, a muscarinic M(1) receptor agonist. Taken together these findings suggest that schizandrin reverses scopolamine-induced memory impairment, in part, by enhancing cholinergic function, and that schizandrin might be useful for treating memory deficits.

[Lignans from different processed products of Schisandra chinensis fruits]

To study the lignan components of different processed products of Schisandra chinensis fruits, the study was conducted with electrospray ionization mass spectrometry (ESI-MS) and high performance liquid chromatography (HPLC). There was no new lignan components detected from the products obtained with different processed methods, the difference was in the content of lignan components. The method is accurate and effective, which can be used to evaluate the quality of different processed products of Schisandra chinensis fruits.

Neglschisandrins C-D: two new dibenzocyclooctadiene lignans from Schisandra neglecta

Two new dibenzocyclooctadiene lignans, neglschisandrins C-D (1-2), were isolated from the stems of Schisandra neglecta. Their structures and stereochemistries were elucidated by spectroscopic methods, including 1D- and 2D-NMR and HR-ESI-MS techniques.

Neglschisandrins A-B: two new dibenzocyclooctene lignans from Schisandra neglecta

Two new dibenzocyclooctene lignans, neglschisandrins A-B (1-2), were isolated from the stems of Schisandra neglecta. Their structures and stereochemistries were elucidated by spectroscopic methods, including 1D- and 2D-NMR and HR-ESI-MS techniques.

Compounds from Kadsura heteroclita and related anti-HIV activity

Phytochemical investigation of the stems of Kadsura heteroclita led to isolation of 16 compounds, including the triterpenoid named longipedlactone J (2), and two dibenzocyclooctadiene type lignans named heteroclitin I and J (3, 4). Compounds 8-10, 14, and 15 were weakly active as anti-HIV agents, whereas compounds 6 and 12 exhibited moderate anti-HIV activity with EC50 values of 1.6 microg/mL, and 1.4 microg/mL, therapeutic index (TI) values of 52.9, and 65.9, respectively. Their structures were established by spectroscopic methods, including application of 2D NMR techniques and CD spectra.

Kadsuralignans H-K from Kadsura coccinea and their nitric oxide production inhibitory effects

One new arylnaphthalene lignan named kadsuralignan H ( 1) and three new dibenzocyclooctadiene lignans, named kadsuralignans I ( 2), J ( 3), and K ( 4), respectively, were isolated from an EtOAc fraction of the 80% acetone extract of Kadsura coccinea. The structures were elucidated on the basis of spectroscopic evidence. Compound 1 is the second arylnaphthalene lignan isolated from the Kadsura genus. Compounds 1 and 3 showed inhibitory activity on nitric oxide (NO) production by the murine macrophage-like cell RAW264.7, which was activated by lipopolysaccharide (LPS) and recombinant mouse interferon-gamma (INF-gamma).

[Recent progresses in studies on bioactive lignans from plants]

Lignans are widely existed in natural world with a variety of structures and bioactivities, including anti-tumor, antiinflammatory, anti-viral and hepatoprotective properties. Along with the development of new techniques in phytochemistry and application of advanced drug screening methods, a variety of lignans have been identified and their bioactivities revealed. In this review, we summarized the activities of six different types of lignans, including arylnaphthalene, dibenzylbutyrolactone, tetrahydrofuran, dibenzylbutane, dibenzocyclooctadiene and neolignan, in order to provide an updated overview of this research field.

Inhibitory effect of schizandrin on passive cutaneous anaphylaxis reaction and scratching behaviors in mice

To evaluate the antiallergic effect of the fruit of Schizandra chinensis Baill (Family Magnoliaceae), which inhibited the mouse passive cutaneous anaphylaxis (PCA) reaction in a preliminary experiment, its main constituent, schizandrin, was isolated and its antiallergic effect investigated. Schizandrin inhibited the PCA reaction induced by the IgE-antigen complex, the scratching behaviors induced by compound 48/80 and the serum IgE production induced by ovalbumin. Schizandrin also inhibited the in vitro degranulation of compound 48/80-induced rat peritoneal mast cells and IgE-induced RBL 2H3 cells. Schizandrin reduced the protein expressions of TNF-alpha and IL-4 in IgE-induced RBL 2H3 cells. These findings suggest that schizandrin can improve IgE-induced anaphylaxis and scratching behaviors.

From lactose towards a novel galactosylated cyclooctenone

Lactose was converted into a disaccharide precursor incorporating an allyl vinyl ether substructure within the glucose residue by vinylation, regioselective silylation, tosylation and subsequent elimination. The thermal Claisen rearrangement led to a novel galactosylated cyclooctenone exhibiting a boat-chair conformation.

Cyclooctane tropospheric degradation initiated by reaction with C1 atoms

GOAL, SCOPE AND BACKGROUND

Within the non-methane hydrocarbons, alkanes constitute the largest fraction of the anthropogenic emissions of volatile organic compounds. For the case of cyclic alkanes, tropospheric degradation is expected to be initiated mainly by OH reactions in the gas phase. Nevertheless, C1 atom reaction rate constants are generally one order of magnitude larger than those of OH. In the present work, the reaction of cyclooctane with C1 atoms has been studied within the temperature range of 279-333 K.

METHODS

The kinetic study has been carried out using the fast flow tube technique coupled to mass spectrometry detection. The reaction has been studied under low pressure conditions, p=1 Torr, with helium as the carrier gas.

RESULTS

The measured room temperature rate constant is very high, k=(2.63+/-0.54)x10-10 cm(3)molecule(-1)s(-1), around 20 times larger than that for the corresponding OH reaction. We also report the results of the rate coefficients obtained at different temperatures: k = (3.5+/-1.2)x 10(-10) exp[(-79+/-110)/T] cm(3) molecule(-1) s(-1) within the range of 279-333 K. This reaction shows an activation energy value close to zero.

DISCUSSION

Quantitative formation of HCl has been observed, confirming the mechanism through H-atom abstraction. The reactivity of cyclic alkanes towards Cl atoms is clearly dependent on the number of CH2 groups in the molecule, as is shown by the increase in the rate constant when the length of the organic chain increases. This increase is very high for the small cyclic alkanes and it seems that the reactions are approaching the collision-controlled limit for cyclohexane and cyclooctane. Conclusions. These results show that gas-phase reaction with Cl in marine or coastal areas is an efficient sink (competing with the gas phase, OH initiated degradation) for the Earth's emissions of cyclooctane, with a Cl-based lifetime ranging from 11 to 2000 hours, depending on the location and time of day.

RECOMMENDATIONS AND PERSPECTIVES

Cl and OH fast reactions with cyclooctane are expected to define the lifetime of cyclooctane emissions to the atmosphere. The degradation of cyclooctane occurs in a short period of time and consequently (under conditions of low atmospheric mass transport), close to the emission sources enabling a significant contribution to local effects, like the formation of photochemical smog.