Antioxidant, antitubercular and cytotoxic activities of Piper imperiale

Phenolic compounds are widely distributed in Nature and act as pharmacologically active constituents in many herbal medicines. They have multiple biological properties, most notably antioxidant, antibacterial and cytotoxic activities. In the present study an attempt to correlate the phenolic composition of leaf, flower and wood extracts of Piper imperiale, with antioxidant, antitubercular and cytotoxic activities was undertaken. The total phenol content ranged from 1.98 to 6.94 mg GAE/gDW among ethanolic extracts, and gallic acid, catechin, epicatechin, ferulic acid, resveratrol and quercetin were identified and quantified by HPLC. DPPH and ABTS assays showed high antioxidant activity of the leaf extract (EC(50ABTS) = 15.6 μg/mL, EC(50DPPH) = 27.3 μg/mL) with EC?? in the same order of magnitude as the hydroxyquinone (EC(50ABTS) = 10.2 μg/mL, EC(50DPPH) = 15.7 μg/mL). The flower extract showed strong antimicrobial activity against Mycobacterium tuberculosis H??Rv. All the extracts exhibited dose-dependent cytotoxic effects against MCF-7 cancer cells. This is the first time that a Piper extract has been found to be highly active against M. tuberculosis. This study shows the biological potential of Piper imperiale extracts and gives way to bio-guided studies with well-defined biological activities.     

Synthesis and antibacterial evaluation of a new series of N-Alkyl-2-alkynyl/(E)-alkenyl-4-(1H)-quinolones

To gain further insight into the structural requirements of the aliphatic group at position 2 for their antimycobacterial activity, some N-alkyl-4-(1H)-quinolones bearing position 2 alkynyls with various chain length and triple bond positions were prepared and tested for in vitro antibacterial activity against rapidly-growing strains of mycobacteria, the vaccine strain Mycobacterium bovis BCG, and methicillin-resistant Staphylococcus aureus strains, EMRSA-15 and -16. The compounds were also evaluated for inhibition of ATP-dependent MurE ligase of Mycobacterium tuberculosis. The lowest MIC value of 0.5 mg/L (1.2-1.5 μM) was found against M. fortuitum and M. smegmatis. These compounds displayed no or only weak toxicity to the human lung fibroblast cell line MRC-5 at 100 μM concentration. The quinolone derivatives exhibited pronounced activity against the epidemic MRSA strains (EMRSA-15 and -16) with MIC values of 2-128 mg/L (5.3-364.7 μM), and M. bovis BCG with an MIC value of 25 mg/L (66.0-77.4 μM). In addition, the compounds inhibited the MurE ligase of M. tuberculosis with moderate to weak activity showing IC50 values of 200-774 μM. The increased selectivity towards mycobacterial bacilli with reference to MRC-5 cells observed for 2-alkynyl quinolones compared to their corresponding 2-alkenyl analogues serves to highlight the mycobacterial specific effect of the triple bond. Exploration of a terminal bromine atom at the side chain of N-alkyl-2-(E)-alkenyl-4-(1H)-quinolones showed improved antimycobacterial activity whereas a cyclopropyl residue at N-1 was suggested to be detrimental to antibacterial activity.     

Precursor chemistry for TiO2: titanium complexes with a mixed nitrogen/oxygen ligand sphere

Novel mixed amido-malonato complexes of titanium are reported. The complexes were synthesized by partially replacing the amido groups from the complexes [Ti(NMe2)4] and [Ti(NEt2)4] via Br?nstedt acid/base reactions, using the malonate-ligands di-isopropylmalonate (Hdpml) and di-tert-butylmalonate (Hdbml). Four representative complexes were synthesized and fully characterised by 1H NMR, 13C NMR, CHN analysis and mass spectrometry. The crystal structures of the six-coordinated complexes [Ti(NMe2)2(dbml)2] (3) and [Ti(NEt2)2(dbml)2] (4) are presented and discussed. The complexes are solids and the chemical and thermal characteristics of the complexes strongly depend on the substitution at the malonate ligand. While dpml containing complexes show a promising behaviour for classical MOCVD, dbml containing complexes seem to be more suitable for liquid injection-metal-organic chemical vapour deposition (LI-MOCVD). Based on its thermal characteristics, the most promising complex for thermal CVD, [Ti(NEt2)2(dpml)2] (2) was selected for preliminary MOCVD experiments, which indicate a good suitability for the deposition of TiO2 thin films.     

Crystal Dynamics in Multi‐stimuli‐Responsive Entangled Metal–Organic Frameworks

An understanding of solid‐state crystal dynamics or flexibility in metal–organic frameworks (MOFs) showing multiple structural changes is highly demanding for the design of materials with potential applications in sensing and recognition. However, entangled MOFs showing such flexible behavior pose a great challenge in terms of extracting information on their dynamics because of their poor single‐crystallinity. In this article, detailed experimental studies on a twofold entangled MOF ( f‐MOF‐1) are reported, which unveil its structural response toward external stimuli such as temperature, pressure, and guest molecules. The crystallographic study shows multiple structural changes in f‐MOF‐1 , by which the 3 D net deforms and slides upon guest removal. Two distinct desolvated phases, that is, f‐MOF‐1 a and f‐MOF‐1 b , could be isolated; the former is a metastable one and transformable to the latter phase upon heating. The two phases show different gated CO₂ adsorption profiles. DFT‐based calculations provide an insight into the selective and gated adsorption behavior with CO₂ of f‐MOF‐1 b . The gate‐opening threshold pressure of CO₂ adsorption can be tuned strategically by changing the chemical functionality of the linker from ethanylene (?CH₂?CH₂?) in f‐MOF‐1 to an azo (?N=N?) functionality in an analogous MOF, f‐MOF‐2 . The modulation of functionality has an indirect influence on the gate‐opening pressure owing to the difference in inter‐net interaction. The framework of f‐MOF‐1 is highly responsive toward CO₂ gas molecules, and these results are supported by DFT calculations.     

Surface functionalization of quantum dots for biological applications

Quantum dots are a group of inorganic nanomaterials exhibiting exceptional optical and electronic properties which impart distinct advantages over traditional fluorescent organic dyes in terms of tunable broad excitation and narrow emission spectra, signal brightness, high quantum yield and photo-stability. Aqueous solubility and surface functionalization are the most common problems for QDs employed in biological research. This review addresses the recent research progress made to improve aqueous solubility, functionalization of biomolecules to QD surface and the poorly understood chemistry involved in the steps of bio-functionalization of such nanoparticles.     

Protein adsorption onto nanomaterials for the development of biosensors and analytical devices: A review

An important consideration for the development of biosensors is the adsorption of the biorecognition element to the surface of a substrate. As the first step in the immobilization process, adsorption affects most immobilization routes and much attention is given into the research of this process to maximize the overall activity of the biosensor. The use of nanomaterials, specifically nanoparticles and nanostructured films, offers advantageous properties that can be fine-tuned to maximize interactions with specific proteins to maximize activity, minimize structural changes, and enhance the catalytic step. In the biosensor field, protein–nanomaterial interactions are an emerging trend that span across many disciplines. This review addresses recent publications about the proteins most frequently used, their most relevant characteristics, and the conditions required to adsorb them to nanomaterials. When relevant and available, subsequent analytical figures of merits are discussed for selected biosensors. The general trend amongst the research papers allows concluding that the use of nanomaterials has already provided significant improvements in the analytical performance of many biosensors and that this research field will continue to grow.     

Oxidation of butane-1,3-, butane-1,4-, 2-methyl pentane-2,4- and 3-methyl pentane-2,4-diols by cerium(IV) in aqueous acidic medium catalyzed by rhodium(III)

The oxidation kinetics of butane-1,3-diol, butane-1,4-diol, 2-methyl pentane-2,4-diol and 3-methyl pentane-2,4-diol with cerium(IV) catalyzed by rhodium(III) in aqueous sulfuric acid showed a peculiar nature with respect to the variation in oxidant concentration, such that the reaction follows first-order kinetics in [Ce(IV)] at low [Ce(IV)] and then reaches a maximum with increasing [Ce(IV)], beyond which further increase in the oxidant concentration retards the rate. The rate shows direct proportionality with respect to [diol] at low concentrations, becoming independent of [diol] at higher concentrations. The rate is first order in catalyst. Retarding effects are observed when [H⁺] and [Ce(III)] are increased, while [Cl⁻] and hence ionic strength have a positive effect on the rate. Spectroscopic studies confirmed that the primary hydroxyl groups in butane-1,3-diol and butane-1,4-diol resulted in the formation of 3-hydroxy butanal and 4-hydroxy butanal, respectively. In the case of oxidation of the secondary hydroxyl groups in 2-methyl pentane-2,4-diol and 3-methyl pentane-2,4-diol, the products of oxidation were 4-hydroxy-4-methyl pentan-2-one and 4-hydroxy-3-methyl pentan-2-one, respectively.     

Nocardioazines: a novel bridged diketopiperazine scaffold from a marine-derived bacterium inhibits P-glycoprotein

An Australian marine sediment-derived isolate, Nocardiopsis sp. (CMB-M0232), yielded a new class of prenylated diketopiperazine, indicative of the action of a uniquely regioselective diketopiperazine indole prenyltransferase. The bridged scaffold of nocardioazine A proved to be a noncytotoxic inhibitor of the membrane protein efflux pump P-glycoprotein, reversing doxorubicin resistance in a multidrug resistant colon cancer cell.     

Electroinitiated Polymerization of Styrene in a Mixed Two-Phase Medium

In extension of our earlier work on electroinitiated polymerization in biphasic media, the electroinitiated polymerization of styrene has been studied using a mixed two-phase system in which formamide together with some added electrolyte is used as the polar phase and the monomer in the bulk form as the nonpolar phase. Among a series of zinc and ferric salts used as the electrolyte, ZnBr₂ was found to be the most effective. The polymer obtained has a molecular weight of 44–47 ± 10³. The effects of various other parameters, such as the dependence of polymer yield on current, the concentration of the electrolyte, the temperature, and the stirring, have also been examined, and a plausible mechanism based on the electrochemical formation of radicals involving a CT complex has been suggested.