Bioassay-Guided Isolation and Identification of Antiplasmodial Compounds from the Stem Bark of Clausena excavata.

Clausena excavata is a medicinal plant widely distributed in Southeast Asia. It is used for a variety of indications, including to treat malaria. In our present study, a phytochemical study of the methanol extract from the stem bark of C. excavata led to the isolation of five pyranocoumarins, nordentatin (1: ), dentatin (2: ), kinocoumarin (3: ), clausarin (4: ), and clausenidin (5: ), and a coumarin, 8-hydroxy-3″,4″-dihydrocapnolactone-2',3'-diol (6: ). The isolation of compound 6: from C. excavata and the antiplasmodial activities against a multidrug-resistant K1 strain of Plasmodium falciparum of 1, 3: , and 5: were reported for the first time. Compounds 3: and 4: exhibited potent antiplasmodial activities with EC50 values of 1.10 and 0.58 µM, respectively, while 1: and 5: had EC50 values of 5.62 and 7.15 µM, respectively. A prenyl group attached to the C-3 or C-12 position on the pyranocoumarin ring probably plays an important role on the activity. A hydroxyl group at the C-10 position is also likely to enhance the activity.

Polydiacetylene rhodamine-based colorimetric chemosensor for Au3+ detection.

A novel platform of a polydiacetylene combined with rhodamine B (PDA-Rho) colorimetric chemosensor array was prepared from a diacetylene monomer and rhodamine B derivative. Rhodamine B derivative as the ion-recognition element was embedded in the polydiacetylene matrix. To fabricate chemosensor, diacetylene monomer connected rhodamine B derivatives (DA-Rho) was coated onto a filter paper surface via drop-casting technique and transformed to polydiacetylene by polymerisation through ultraviolet (UV) irradiation. From the result, PDA-Rhoen exhibited high sensitivity and selectivity for Au3+ and could be monitored directly by naked eyes providing a fast, portable and easy-to-use as a molecular device in the real system. The DFT calculation results showed a stable complex between PDA-Rho and Au3+. We believe that, this method offers a sensitive and accurate process for Au3+ ion detection in real environmental and biological applications.

Characterisation of indole alkaloids and phenolic acids from wild mushroom Tropicoporus linteus and its chemical profiles compared with other Sanghuang mushrooms.

Two new indole alkaloids, 1-methylindole-7-methoxy-3-carboxaldehyde (2) and 7-methoxyindole-3-carboxaldehyde (4), together with 7-methoxyindole-3-carboxylic acid methyl ester (1) and 1-methylindole-3-carbaldehyde (3) were isolated from the fruiting bodies of wild Sanghuang mushroom Tropicoporus linteus (TL663). TLC, 1H-NMR and LC-MS chemical profiles of this mushroom compared with other three genera of wild Sanghuang mushroom extracts were investigated. The TLC, 1H-NMR and LC-MS profiles of TL663 and Sanghuangporus sanghuang (SS664) were similar and significantly different from other mushrooms. These two samples indicated the same TLC chromatograms by showing prominent bands of 1 - 4 when observed under UV 254 nm and having sharp aldehyde proton signals of 3-carboxaldehyde indole type in 1H-NMR spectra. From LC-MS analyses, peaks of isolated compounds 1 - 4 and indole-3-carboxaldehyde (5) in TL663 extract and peaks of protocatechuic acid (6), caffeic aldehyde (7), caffeic acid (8) and 3,4-dihydroxybenzalacetone (9) phenolic acids in TL663 fraction were identified.

An ultra-low detection limit gold(III) probe based on rhodamine-covalent hydrogel sensor.

A highly sensitive and selective optical chemosensor (Arg-Rhoen) for determination of Au3+ was prepared by covalent immobilization of rhodamine ethylenediamine on agarose gel. Spectrophotometric studies of complex formation, chemical structures and purity of the hydrogel sensor were carried out using TGA, NMR, TEM, and IR. The complexation study results indicated that this probe can selectively detect Au3+ via a metal ion chelation-induced ring-opening reaction, and then caused a remarkable colour change from colourless to pink and a strong fluorescence enhancement. Theoretical DFT calculation results suggested that the hydrogel sensor Arg-Rhoen formed stable complexes with Au3+ through a large number of cation-dipole interactions. Reusability has been established by repeatedly dipping and rinsing the hydrogel in aqueous Au3+ and EDTA in basic solutions. We believe that this approach may provide an easily measurable and inherently sensitive method for Au3+ detection in environmental and biological applications.

Immobilization of unmodified aminoanthraquinone derivatives onto silica gel surface for solid-phase extraction and pre-concentration of Pb(II).

In this project, silica gel chemically bonded with derivatives of aminoanthraquinone were synthesized and characterized. Adsorbents 1,8-aminoanthraquinone-3-aminopropylsilica (SL1), 2-aminoanthraquinone-3-aminopropylsilica (SL2) and 1-aminoanthraquinone-3-aminopropylsilica (SL3) were produced and tested to adsorb heavy metal solutions including Pb(II) Cu(II) Zn(II) Cd(II) and Co(II). The concentrations of the adsorbed heavy metals solution were calculated by atomic adsorption spectrophotometry employing a batch method. The results showed that speed at 200 rpm for 30 min with pH 9 is the optimum condition for heavy metal adsorption. The result also indicated that adsorbent SL3 is the best adsorbent for Pb(II) at 82.5%, and the relative standard deviation (R.S.D.) was lower than 6%. The method detection limit was 1.1 µg L-1 for Pb2+. In addition, Density Functional Theory (DFT) calculation results suggested that the adsorbent sensor formed stable complexes with Pb(II) through a large number of cation-dipole interactions. The method was also applied with satisfactory results to the pre-concentration of trace Pb(II) in environmental samples.

Gold sensing with rhodamine immobilized hydrogel-based colorimetric sensor.

A highly sensitive and selective optical membrane for determination of Au3+ was synthesized by immobilization of a rhodamine derivative on agarose hydrogel. The sensing dye was synthesized by solvatochromism of rhodamine B via rhodamine lactone-zwitterion equilibrium. UV-vis spectroscopy, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were employed to confirm that the rhodamine-lactone (RhoL) was incorporated into the agarose hydrogel. The results showed that the sensor was highly selective for recognizing Au3+ over other metal ions in real systems. In addition, DFT calculation results suggested that the membrane sensor formed stable complexes with Au3+ through a large number of cation-dipole and ion-ion interactions. In addition, according to changes in signaling upon adding various Au3+ concentration, the limit of detection of Arg-RhoL for Au3+ is calculated to be 5 µM. This approach may provide an easily measurable and inherently sensitive method for Au3+ ion detection in environmental and biological applications.

Facile synthesis of rhodamine-based highly sensitive and fast responsive colorimetric and off-on fluorescent reversible chemosensors for Hg2+: preparation of a fluorescent thin film sensor.

Fluorescence-active chemosensors (L1-L4), comprising a rhodamine scaffold and a pseudo azacrown cation-binding subunit, have been proposed and characterized as a fluorescent chemosensor for Hg(2+). An on-off type fluorescent enhancement was observed by the formation of the ring-opened amide form of the rhodamine moiety, which was induced by the interactions between Hg(2+) and the chemosensor. Upon the addition of Hg(2+), an overall emission change of 350-fold was observed, and the selectivity was calculated to be 300 times higher than Cu(2+) for receptors L2-L4. A polymeric thin film can be obtained by doping poly(methyl methacrylate) or PMMA with chemosensor L2. Such a thin film sensor can be used to detect Hg(2+) with high sensitivity and can be recovered using diluted NaOH.

Design and synthesis of thiourea based receptor containing naphthalene as oxalate selective sensor.

The thiourea based receptor containing naphthalene groups (1), has been successfully designed and synthesized for application as an oxalate receptor. A density functional theory at B3LYP/6-31G(d,p) level of theory has been applied to predict the binding ability between 1 and selected anions, i.e., oxalate, malonate, succinate, glutarate, dihydrogen phosphate, and hydrogen sulphate. Calculation results point out that receptor 1 shows the strongest interaction to oxalate ion with the binding free energy of 172.48 kcal mol(-1). The recognition ability of 1 to the selected anions has been also investigated by means of the absorption and emission techniques. Experimental results are in excellent agreement with the calculation data in which receptor 1 shows highly selective for oxalate ion over the other anions with logbeta of 3.82 (0.02) M(-1) by means of the size of binding cavity.

Conformation-selective synthesis and binding properties of N-benzylhexahomotriaza-p-chlorocalix[3]trinaphthylamide.

N-benzylhexahomotriaza-p-chlorocalix[3]trinaphthylamide in partial cone conformation was selectively synthesized by appropriately controlling the steric effect during the amidation reactions of N-benzylhexahomotriaza-p-chlorocalix[3]tri(ethyl acetate) in cone or partial cone conformations with use of 1-aminomethylnaphthalene. The conformation was confirmed by (1)H, (13)C, and 2D NMR and X-ray single-crystal analysis. Analyses of the complexes revealed that recognition is strongly affected by Cd(2+), Pb(2+), and F(-) ions.

Self-assembly and electrochemical oxidation of polyamidoamine-carbazole dendron surfmer complexes: nanoring formation.

We report a detailed and quantitative study on the supramolecular complexation of amine-functionalized polyamidoamine (PAMAM) dendrimer G(4)-NH(2) with carboxylic acid terminal dendrons containing peripheral electroactive carbazole groups of different generations (G(0)COOH, G(1)COOH, and G(2)COOH). While the focus is on a detailed understanding and mechanism of complex formation, subsequent electrochemical oxidation of the dendron surfmers resulted in the formation of nanoring structures electrodeposited on the conducting substrate. Complexation was confirmed by NMR, UV-vis, and IR measurements. Critical micelle concentration (CMC), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) studies revealed that the ringlike structures were formed during the equilibrium-decomplexation stage and that the electrochemical process did not destroy the complex but rather stabilized it. The different generations of the dendrons provided various structures and complex formation efficacy. This type of template polymerization combined with electrochemically anodic oxidation has not been previously reported.

Novel C3v-symmetrical N7-Hexahomotriazacalix[3]cryptand: a highly efficient receptor for halide anions.

[structure: see text] We report the synthesis of a novel C(3)(v)()-symmetrical N(7)-hexahomotriazacalix[3]cryptand (1). Compound 1 was shown to be in a fixed cone conformation by (1)H NMR spectroscopy and X-ray single-crystal structure determination. Complexation studies showed that 1 is a selective receptor for halide ions. The effects of zinc metal cation on the receptor (1-Zn(2+)) upon anion recognition are also shown.