Lithium adduct as precursor ion for sensitive and rapid quantification of 20 (S)‐protopanaxadiol in rat plasma by liquid chromatography/quadrupole linear ion trap mass spectrometry and application to rat pharmacokinetic study

A novel, rapid and sensitive liquid chromatography/quadrupole linear ion trap mass spectrometry [LC‐ESI‐(QqLIT)MS/MS] method was developed and validated for the quantification of protopanaxadiol (PPD) in rat plasma. Oleanolic acid (OA) was used as internal standard (IS). A simple protein precipitation based on acetonitrile (ACN) was employed. Chromatographic separation was performed on a Sepax GP‐C₁₈ column (50 × 2.1 mm, 5 μM) with a mobile phase consisting of ACN–water and 1.5 μM formic acid and 25 mM lithium acetate (90 : 10, v/v) at a flow rate of 0.4 ml/min for 3.0 min. Multiple‐reaction‐monitoring mode was performed using lithium adduct ion as precursor ion of m/z 467.5/449.4 and 455.6/407.4 for the drug and IS, respectively. Calibration curve was recovered over a concentration range of 0.5–100 ng/ml with a correlation coefficient >0.99. The limit of detection was 0.2 ng/ml in rat plasma for PPD. The results of the intraday and interday precision and accuracy studies were well within the acceptable limits. The validated method was successfully applied to investigate the pharmacokinetic study of PPD after intravenous and gavage administration to rat. Copyright © 2013 John Wiley & Sons, Ltd.     

An interesting two‐phase solvent system and its use in preparative isolation of aconitines from aconite roots by counter‐current chromatography

Two‐phase solvent system plays crucial role in successful separation of organic compounds using counter‐current chromatography (CCC). An interesting two‐phase solvent system, composed of chloroform/ethyl acetate/methanol/water, is reported here, in which both phases contain sufficient organic solvents to balance their dissolving capacities. Adjusting the solvent system to get satisfactory partition coefficients (K values) for target compounds becomes relatively simple. This solvent system succeeded in sample preparation of aconitine (8.07 mg, 93.69%), hypaconitine (7.74 mg, 93.17%), mesaconitine (1.95 mg, 94.52%) from raw aconite roots (102.24 mg, crude extract), benzoylmesaconine (34.79 mg, 98.67%) from processed aconite roots (400.01 mg, crude extract), and yunaconitine (253.59 mg, 98.65%) from a crude extract of Aconitum forrestii (326.69 mg, crude extract).     

Graphene‐based solid‐phase extraction disk for fast separation and preconcentration of trace polycyclic aromatic hydrocarbons from environmental water samples

Graphene has great potentials for the use in sample preparation due to its ultra high specific surface area, superior chemical stability, and excellent thermal stability. In our work, a novel graphene‐based SPE disk was developed for separation and preconcentration of trace polycyclic aromatic hydrocarbons from environmental water samples. Based on the strong π–π stacking interaction between the analytes and graphene, the analytes extracted by graphene were eluted by cyclohexane and then determined by GC‐MS. Under the optimized conditions, high flow rate (30 mL/min) and sensitivity (0.84–13 ng/L) were achieved. The proposed method was successfully applied to the analysis of real environmental water samples with recoveries ranging from 72.8 to 106.2%. Furthermore, the property of anticlogging and reusability was also improved. This work reveals great potentials of graphene‐based SPE disk in environmental analytical.     

Tuning the frontier molecular orbital energy levels of n‐type conjugated copolymers by using angular‐shaped naphthalene tetracarboxylic diimides,and their use in all‐polymer solar cells with high open‐circuit voltages

An angular‐shaped naphthalene tetracarboxylic diimide (NDI) was designed and synthesized as a new building block for n‐type conjugated polymers to tune their energy levels. Three n‐type copolymers incorporating this angular‐shaped NDI as the acceptor moiety were obtained by Stille coupling reactions and had number average molecular weights of 18.7–73.0 kDa. All‐polymer bulk‐heterojunction solar cells made from blends of these polymers with poly(3‐hexylthiophene) gave a power conversion efficiency up to 0.32% and exhibited an open‐circuit voltage (V_oc) up to 0.94 V due to their relative high‐lying lowest unoccupied molecular orbital energy levels. The high V_oc of 0.94 V is higher than that of solar cells based on linear‐shaped NDI‐containing polymers (<0.6 V). The results indicate that the angular‐shaped NDI is a promising building block for constructing nonfullerene polymer acceptors for solar cells with high open‐circuit voltages. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Copper-Catalyzed Cyanopropylation of Activated Alkenes

A practical copper-catalyzed alkylarylation of activated alkenes with azobisisobutyronitrile (AIBN) and beyond has been developed, in which incorporation of 3^o nitrile moiety into an oxindole scaffold proceeded smoothly through cascade radical addition/C(sp²)-H cyclization. The use of readily available AIBN as radical source and inexpensive CuI as catalyst, as well as broad substrate scope and the simplicity of operation and handling, make this protocol a highly attractive approach to oxindoles bearing 3^o nitrile moiety.     

The role of benzoic acid in proline‐catalyzed asymmetric michael addition: A density functional theory study

In asymmetric Michael addition between ketones and nitroolefins catalyzed by L ‐proline, we observed that it was benzoic acid or its derivatives rather than other proton acid that could accelerate the reaction greatly, and different benzoic acid derivatives brought different yields. To explain the experimental phenomena, a density functional theory study was performed to elucidate the mechanism of proline‐catalyzed asymmetric Michael addition with benzoic acid. The results of the theoretical calculation at the level of B3LYP/6‐311+G(2df,p)//B3LYP/6‐31G(d) demonstrated that benzoic acid played two major roles in the formation of nitroalkane: assisting proton transfer and activating the nitro group. In the stage of enamine formation from imine, the energy profiles of benzoic acid derivatives were also calculated to investigate the reasons why different benzoic acid derivatives caused different yields. The results demonstrated that the pK_a value was the major factor for p‐substituted benzoic acid derivatives to improve the yields, whereas for m/o‐substituted benzoic acid derivatives, both pK_a value and electronic and steric effects could significantly increase the yields. The calculated results would be very helpful for understanding the reaction mechanism of Michael addition and provide some insights into the selection of efficient additives for similar experiments. © 2012 Wiley Periodicals, Inc.     

Continuous Detection of pH‐responsive Drug Delivery System in Cells in situ by Confocal Laser Scanning Microscopy

Mesoporous silica nanoparticles (MSN) were coated by pH‐responsive polymer chitosan‐poly (methacrylic acid) (CS‐PMAA). This nano drug delivery system showed good application prospects and the polymer‐coated microspheres were promising site‐specific anticancer drug delivery carriers in biomedical field. A continuous detection of pH‐responsive drug delivery system in cells in situ, utilizing MSN/CS‐PMAA composite microspheres, was proposed. Two kinds of different cell lines, tumor cell line (Hela) and normal somatic cells (293T), were used to investigate the behaviours of the drug loaded system in the cells. Conclusions could be drawn from the fluorescent images obtained by confocal laser scanning microscopy (CLSM), modified drug‐loaded microspheres (MSN/CS‐PMAA) were ingested into cells more easily, the uptake of DOX@FITC‐MSN/CS‐PMAA by HeLa/293T cells were performed at pH 7.4/pH 6.8, DOX was released during the ingestion process, fluorescence intensity decreased with time because of efflux transport and photo‐bleaching. Fluoresence detection by flow cytometry was performed as comparison. The continuous fluorescent observation in situ could be widely used in the pH‐responsive releasing process of drug delivery system in the cells.     

Novel Synthesis of Aza-phthalimidine Hydroxylactams

A novel and convenient synthetic route for preparing aza-phthalimidine hydroxylactams (5a–j) by N-bromosuccinimide (NBS) was developed. This method involved the substitution reactions of substrates (3a–j) with NBS via unstable intermediate bromides (4a–j) rapidly hydrolyzed into hydroxyl products in the course of the workup process.     

Two lanthanum(III) complexes containing η2‐pyrazolate and η2‐1,2,4‐triazolate ligands: intramolecular C—H...N/O interactions and coordination geometries

The lanthanum(III) complexes tris(3,5‐diphenylpyrazolato‐κ²N,N′)tris(tetrahydrofuran‐κO)lanthanum(III) tetrahydrofuran monosolvate, [La(C₁₅H₁₁N₂)₃(C₄H₈O)₃]·C₄H₈O, (I), and tris(3,5‐diphenyl‐1,2,4‐triazolato‐κ²N¹,N²)tris(tetrahydrofuran‐κO)lanthanum(III), [La(C₁₄H₁₀N₃)₃(C₄H₈O)₃], (II), both contain La^III atoms coordinated by three heterocyclic ligands and three tetrahydrofuran ligands, but their coordination geometries differ. Complex (I) has a mer‐distorted octahedral geometry, while complex (II) has a fac‐distorted configuration. The difference in the coordination geometries and the existence of asymmetric La—N bonding in the two complexes is associated with intramolecular C—H...N/O interactions between the ligands.     

CO加氢制备低碳烯烃Fe基、Co基催化剂研究进展

CO加氢制备低碳烯烃是非石油路线获得烯烃的重要反应,其反应路线有直接法和间接法。直接法制备低碳烯烃具有反应路线短、能源利用率高、经济高效等优势。综述了近年来Fe基催化剂、Co基催化剂在CO直接制备低碳烯烃中的研究进展。分析认为：费托合成过程产物选择性遵循Anderson-Schulz-Flory（ASF）分布规律,助剂和载体的使用一定程度提高Fe基、Co基催化剂的低碳烯烃选择性。