A Six-Coordinate Picrate Nickel(II) Complex Based on the V-Shaped Ligand 1,3-Bis (1-Benzylbenzimidazol-2-yl)-2-Thiapropane: Synthesis,Crystal Structure,Biological Activities

Abstract

A six-coordinate picrate nickel(II) complex based on the V-shaped ligand 1,3-bis(1-benzylbenzimidazol-2-yl)-2-thiapropane (L), with the composition [Ni(L)₂](pic)₂, has been synthesized and characterized systematically. The crystal structure of the Ni(II) complex is a six-coordinated octahedron, which is considerably close to ideal octahedral geometry with N₄S₂ donors of the two ligands. Biological activities of compounds were investigated using electronic absorption spectroscopy, fluorescence spectroscopy, and viscosity measurements. The results suggested that both ligand L and Ni(II) complex bind to DNA in an intercalative binding mode, and DNA-binding affinity of the Ni(II) complex is stronger than that of ligand L.

[Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental files: Additional figures.]     

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.     

气相色谱法检测月饼中的脱氢乙酸

应用硫酸锌试剂沉淀月饼样品中的蛋白,乙醚提取样品中的脱氢乙酸,建立了Rtx-5弱极性毛细管柱-气相色谱分离检测月饼中的脱氢乙酸的方法。经方法验证,方法的检出限为0.24μg/mL,定量下限为0.32μg/mL,在0.0～0.5 mg/mL浓度范围内脱氢乙酸的浓度与色谱峰面积呈良好线性关系,相关系数r2=0.999 5,加标回收率在87.9%～94.4%之间,测定结果的相对标准偏差为2.5%(n=12)。该方法样品处理简单,适合月饼中脱氢乙酸的定量分析检测。     

Comparison of sample preparation methods combined with gas chromatography with electron‐capture detection for the analysis of multipesticide residues in lotus seeds

Sample preparation is always the major bottleneck in analytical chemistry for the determination of pesticide residues. Different sample preparation methods have been proposed due to the wide variety of pesticides used and the inherent complexity of the matrices. In this study, different sample preparation methods including SPE, matrix solid‐phase dispersion, the quick, easy, cheap, efficient, rugged, and safe method, and a one‐step completion method were compared and evaluated for extracting pesticides from lotus seeds. Analysis was carried out using GC with electron‐capture detection. The results showed that good recoveries for tested pesticides were obtained by using Florisil in the four methods, and the extraction efficiency of the one‐step completion method was superior to the other three methods. The one‐step completion method was confirmed to have good linearity, reproducibility, stability, and recovery for the detection of 36 pesticides in lotus seed samples. The data collected from this study are expected to prove useful in regulating the concentration of the residues in lotus seeds, as well as in protecting human health from the hazards posed by these residues.     

A colormetric and fluorescent chemosensor for adenosine-5′-triphosphate based on rhodamine derivative

A rhodamine spirolactam derivative (1) was developed as a colormetric and fluorescent chemosensor for adenosine-5′-triphosphate (ATP) via hydrogen bonds interaction. As far as we know, this is the first case to explore ATP-induced ring-opening of spirolactam in rhodamine derivatives. It exhibited a highly sensitive “turn-on” fluorescent response toward ATP with a 47-fold fluorescence intensity enhancement under 20 equiv. of ATP added. The chemosensor can be applied to the quantification of ATP with a linear range covering from 1.0 × 10⁻⁷ to 2.0 × 10⁻⁴ M and a detection limit of 2.5 × 10⁻⁸ M. The experiment results show that the response behavior of 1 toward ATP is pH independent in medium condition (pH 6.0–8.0). Most importantly, the novel chemosensor has well solved the problem of serious interferences from other nucleoside polyphosphates such as ADP and AMP generally met by previously reported typical fluorescent chemosensors for ATP. Moreover, the response of the chemosensor toward ATP is fast (response time less than 3 min). In addition, the chemosensor can be used for the fluorescence assay for protein kinase activity with satisfactory results. The chemosensor for ATP based on hydrogen bonds interaction provided a novel strategy for the design of colormetric and ratiometric fluorescent probes for other target anions with high sensitivity and selectivity.     

Development of a sensitive and reliable high performance liquid chromatography method with fluorescence detection for high-throughput analysis of multi-class mycotoxins in Coix seed

As an edible and medicinal plant, Coix seed is readily contaminated by more than one group of mycotoxins resulting in potential risk to human health. A reliable and sensitive method has been developed to determine seven mycotoxins (aflatoxins B₁, B₂, G₁, G₂, zearalenone, α-zearalenol, and β-zearalenol) simultaneously in 10 batches of Coix seed marketed in China. The method is based on a rapid ultrasound-assisted solid–liquid extraction (USLE) using methanol/water (80/20) followed by immunoaffinity column (IAC) clean-up, on-line photochemical derivatization (PCD), and high performance liquid chromatography coupled with fluorescence detection (HPLC-FLD). Careful optimization of extraction, clean-up, separation and detection conditions was accomplished to increase sample throughput and to attain rapid separation and sensitive detection. Method validation was performed by analyzing samples spiked at three different concentrations for the seven mycotoxins. Recoveries were from 73.5% to 107.3%, with relative standard deviations (RSDs) lower than 7.7%. The intra- and inter-day precisions, expressed as RSDs, were lower than 4% for all studied analytes. Limits of detection and quantification ranged from 0.01 to 50.2 μg kg⁻¹, and from 0.04 to 125.5 μg kg⁻¹, respectively, which were below the tolerance levels for mycotoxins set by the European Union. Samples that tested positive were further analyzed by HPLC tandem electrospray ionization mass spectrometry for confirmatory purposes. This is the first application of USLE-IAC-HPLC-PCD-FLD for detecting the occurrence of multi-class mycotoxins in Coix seed.     

Facile and Rapid Synthesis of 9H-Carbazole-9-Carboxylic Acids Under Microwave Irradiation

The reaction of halogenated 9H-carbazoles or carbazole with bromoesters in DMF under microwave irradiation readily affords a series of 9H-carbazoles-9-hydroxylic acids.     

Polycondensation of Sebacic Acid with Primary and Secondary Hydroxyl Groups Containing Diols Catalyzed by Candida antarctica Lipase B

Abstract

The aliphatic polyesters are normally synthesized by ester interchange reactions or direct esterification of hydroxyacids or diacid/diol combinations. Biotransformation, utilizing the enzymes as catalysts, was accepted as an alternative route for the synthesis of aliphatic polyesters and offers various advantages compared with the conventional, metal-catalyzed polymerization reactions. Previous studies indicated that lipase-catalyzed polycondensation reactions between diols and diacids occurred preferentially at primary hydroxyl groups of diols, when diols contained both primary and secondary hydroxyl groups. In this work, we investigated lipase-catalyzed polycondensation of diacids and secondary hydroxyl group–containing diols, and successfully synthesized polyesters by polycondensation with secondary hydroxyl groups as well as primary hydroxyl groups. Various diols, glycerol, 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, and 2,4-pentanediol were tested for the polycondensation. The polymerization was achieved by heating a mixture of lipase B, sebacic acid, and the diols in anhydrous toluene at 100 °C for 72 h. The resulting polymers were characterized by ¹H and ¹³C NMR spectroscopy, Fourier transform–infrared spectroscopy, thermogravimetric analysis, and gel permeation chromatography.     

Polyethylene Glycol–Enhanced Chemoselective Synthesis of Organic Carbamates from Amines,CO2, and Alkyl Halides

An efficient and environmentally benign method for the synthesis of organic carbamates was developed. Amines, CO₂, and alkyl halides underwent a three-component reaction with the aid of K₂CO₃ and polyethylene glycol (PEG, MW = 400), affording the organic carbamates under ambient conditions. PEG could presumably act as a solvent and phase-transfer catalyst (PTC). Notably, the presence of PEG could also depress the alkylation of both the amine and the carbamate, thus resulting in enhanced selectivity toward the target carbamate.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.