Structural characterization and thermal degradation of poly(methylmethacrylate)/zinc oxide nanocomposites

This work is based on the preparation of composites of poly(methylmethacrylate) with zinc oxide nanoparticles synthesized by solution casting method.

Chloroform cast poly(methylmethacrylate) films containing different amounts of ZnO nanoparticles were characterized by XRD, SEM, UV-vis spectroscopy, FTIR spectroscopy and TGA.

The results show that ZnO nanoparticles with a size of 24?nm were fairly dispersed in the polymer matrix. The obtained material had UV shielding capability with optical transparency. Thermal characterization shows that, the nanocomposites were more thermally stable than pure PMMA presenting three degradation steps. Apparent kinetic parameters were determined for each degradation step using peak fitting methodology. According to activation energies, ZnO particles affect simultaneously but oppositely the kinetics of underlying degradation reactions. Thermal stability of the PMMA/ZnO nanocomposites was the result of the overall balance in favor of the inhibiting effect of ZnO.     

Gas chromatography tandem mass spectrometry for the screening of adulterants in seized captagon™ tablets

Background: Amphetamine type stimulants (ATS) are the second most popular illegal drugs used worldwide, after cannabis. The production of ATS has increased across the world, including the Middle East. Fenethylline (Captagon?), amphetamine derivative, sold as a street drug usually contains several adulterants and diluents. In Saudi Arabia, like other countries, samples of illicit ATS are submitted to laboratories to test for the adulterated compounds.

Objective: The objective of the proposed study was to apply gas chromatography/mass spectrometry (GC/MS) for fenethylline profiling of seized samples collected from the Saudi market (n?=?55).

Methodology: The GC/MS analysis was performed on a general purpose column (30?m?×?0.25?mm i.d) coated with 0.25?µm cross bond, 5% diphenyl dimethyl polysiloxane (Rtx-5MS). The mass was operated in the electron impact mode.

Results and discussion: Analyzed samples gave positive results for amphetamine in the concentration range between 1.35% and 37.32% of the powder, caffeine in the range between 22.74 and 44.92%, in addition to different concentrations of levoglucosenone, theophylline, D-allose, lidocaine, methamphetamine, dextromethorphan, and other adulterants. Finally, the presence of other substances in fenethylline street samples could result in intoxication. This significantly contributes to the potential risk of drug addiction among public.     

Development of new and robust LC-MS method for simultaneous quantification of polyphenols from Sambucus ebulus fruits

A new and simple LC-MS method for analysis of flavonoids from Sambucus ebulus berry extracts was developed and validated. Successfully were quantitated seven polyphenols: epicatechin, epigallocatechin gallate, rutin, resveratrol, myricetin, quercetin, and kaempferol.

Two detectors, working in parallel, were used: photodiode-array and single quadrupole mass-detector. The mass detection was used for identification and quantification of the analytes, while the diode-array detector was as confirmation tool. The following m/z were tracked: 457.15 (epigallocatechin gallate); 289.06 (epicatechin); 609.13 (rutin); 227.05 (resveratrol); 317.0 (myricetin); 301.02 (quercetin); 285.02 (kaempferol). For optimization the chromatographic separation three wavelengths 205?nm, 305?nm, 272?nm were monitored. The method was capable to detect in one run compounds with no UV or fluorescence chromophore and with very similar structures, such as plant polyphenols. The linearity was from 0.05?mg/L to 50?mg/L (R² 0.9962–0.9987). The recoveries for all tested analytes were between 81.6% and 104.7%.

The method was applied for analysis of crude extract of Sambucus ebulus ripe fruits. Three major polyphenols – epicatechin (0.84?mg/100gFW), quercetin (0.15?mg/100gFW) and kaempferol (0.05?mg/100gFW) were identified and quantified.

The proposed method could be successfully used for routine analysis of epigallocatechin gallate, epicatechin, rutin, resveratrol, myricetin, quercetin, and kaempferol in Sambucus ebulus extracts.     

Effect of natamycin on the physicochemical properties of corn starch based films and their effect on Penicillium spp. activity

The incorporation of antimicrobials in foods by means of the use of films where they are entrapped collaborates to decrease their diffusion rate. In this work, the physicochemical properties of starch-based films loaded with 1% wt. natamycin were analyzed, and the antifungal activity of these films was evaluated against Penicillium spp..

Variations in the properties of films with 1% natamycin were minimal, leading to the conclusion that this material could be applied to avoid mold development on the surface semi-hard cheeses. Corn starch-based films containing natamycin at 1% w/w inhibited the Penicillium spp. growth in a solid matrix.     

Synthesis,Crystal Structure and Thermal Decomposition of [HGdP2O7 · 2 H2O] · NH3 Electric properties of HGdP2O7 and Gd2P4O13

A new gadolinium diphosphate [HGdP₂O₇ · 2 H₂O] · NH₃ was synthesized via a soft chemistry route from evaporation of aqueous solution. It crystallizes in the space group Pī with Z = 2 and the following unit cell dimensions: a = 6.4609(2), b = 6.9810(2), c = 9.813(4) ?, α = 81.345(3), β = 80.547(3), γ = 88.430(3)°. IR spectroscopy confirmed the presence of P-OH group, and both ammonia and water molecule in the studied material.

The thermal decomposition of [HGdP₂O₇ · 2 H₂O] · NH₃, as investigated by Controlled Rate Thermal Analysis, took place in three stages between -23 and 600 °C leading to the anhydrous salt HGdP₂O₇. The calcination of the synthesized product at 850 °C in a static air furnace allowed us to obtain the tetraphosphate Gd₂P₄O₁₃. X-ray powder diffraction and infrared spectroscopy were used to identify these materials.

The electrical properties of HGdP₂O₇ and Gd₂P₄O₁₃ were investigated through impedance complex analysis. Modest conductivity has been observed in both materials at relatively medium temperature range. Activation energies of 0.62 and 1.21 eV, were deduced from the Arrhenius plots for HGdP₂O₇ and Gd₂P₄O₁₃, respectively.     

Adsorption of N,N-dimethylamine from aqueous solutions by a metal organic framework,MOF – 235

Water-resistant MOF-235 was used to adsorb N,N-dimethylamine (DMA) from aqueous solutions. It was synthesized from terephthalic acid and FeCl₃.6H₂O under air-free conditions and characterized by its crystalline structure, functional groups and temperature resistance. The kinetic data results were best adjusted to the pseudo-second order model (R²>0.963). The best-fit isotherm, Langmuir model, suggested the adsorption of DMA is localized on homogenously distributed active sites on the surface. This fit was confirmed by the value of β?=?1 on the Redlich-Peterson model. Our study suggests that the manipulation of novel materials such as MOF-235 promises new avenues for water treatment solutions.

Schematic structure of MOF-235 and its application as adsorbent.     

Review: Inverse coordination. Inorganic open and cyclic nitrogen heteroatom molecules as coordination centers. A survey of molecular topologies

This review is a follow up to a previous article [I. Haiduc J. Coord. Chem. (2018) doi:10.1080/00958972.2018.1515429.] which illustrated the concept of inverse coordination with structures in which the coordination center is nitrogen alone (mono- and poly-nitrogen moieties). Here the open and cyclic heteroatom molecules with inorganic skeletons and nitrogen donor sites are presented. Organic nitrogen heterocycles will be treated in a further review.

     

MgFe2O4@SiO2-PrNH2/Pd/bimenthonoxime core-shell magnetic nanoparticles as a recyclable green catalyst for heterogeneous Suzuki cross-coupling in aqueous ethanol

Magnetically recoverable MgFe₂O₄@SiO₂-PrNH₂/Pd/bimenthonoxime nanoparticles were prepared and characterized by SEM, EDX, TEM, XRD, XPS, ICP, VSM and FT-IR. The nanocatalyst was used for Suzuki cross-coupling in aqueous ethanol media, and the corresponding biaryl derivatives were synthesized within short reaction time. The catalyst was separated by an external magnet and reused several times.

     

Hydrolysis of phosphate esters in aqueous solution promoted by cobalt(III)-tetraamine metallohydrolases: Chromatographic and spectroscopic studies

A combination of chromatographic and spectroscopic (Q-ToF/MS; FTIR) studies were conducted to further understand hydrolytic processes in reactions of phosphate mono- and phosphodiesters with model Cobalt(III)-tetraamine metallohydrolases of the type [CoL(OH)(OH₂)]²⁺; L?=?(en)₂, (tn)₂; en?=?1,2-diaminoethane, tn?=?1,3-diaminopropane.

High resolution mass spectroscopic (HRMS) analysis of the reaction fragments indicates that the monoester substrates undergo initial coordination to the metal center followed by an intramolecular hydroxyl attack on phosphorus, a process that is concerted with liberation of the bound alcoholic leaving group. The Co^III(tn)₂ complex displays twice as more reactivity towards both mono- and phosphodiesters compared to the (en)₂ analog under similar conditions, a behavior that is discussed in terms of the structural differences in the coordinated amine ligands. Plausible mechanisms for Co(III)-promoted hydrolysis of both the mono- and phosphodiesters are proposed.     

Synthesis and characterization of photo-crosslinkable copoly (carbonate-ester)s (PCE) derived from p-Hydroxy cinnamic acid (p-HCA) and bisphenol A (BPA)

A series of new copoly(carbonate-ester)s derived from p-hydroxy cinnamic acid (p-HCA) and 2,2-bis-(4-hydroxyphenyl) propane (Bisphenol A, BPA) was synthesized by an interfacial polymerization process. Films of these unsaturated copolymers were exposed to UV-light and sunlight to induce crosslinking. The resulting crosslinked films were insoluble in strong polycarbonate solvents such as dichloromethane and chloroform. The initial optical properties of the film are similar to bisphenol A polycarbonate (BPA-PC) and reduced on exposure to UV and sunlight with time. The Tg’s of copolymers are in the range of BPA-PC and thermal stability is lower than BPA-PC.

The chemical resistance and the dimensional stability of the crosslinked systems are expected to be superior to the ones from BPA-PC. Moreover, the double bond functionality in the p-HCA-containing resin could potentially be used to graft acrylates or other unsaturated monomers onto the copoly (carbonate ester)-backbone.     

Myristigranol,a new diarylpropane derivative from the wood of Myristica fragrans

Myristigranol, a new diarylpropane derivative, was isolated from the methanol extract of Myristica fragrans wood along with one diarylpropanoid and three stilbenoids. The isolated constituents were exhaustingly identified using the analyses of 1D and 2D NMR spectroscopic techniques and comparison of the literatures reported as well. The antioxidant activity was also determined.

     

Phytotoxic metabolites by nine species of Botryosphaeriaceae involved in grapevine dieback in Australia and identification of those produced by Diplodia mutila,Diplodia seriata,Neofusicoccum australe and Neofusicoccum luteum

Botryosphaeria dieback is one of the main trunk diseases of grapevine caused by several species of Botryosphaeriaceae. Twenty-four fungal isolates representing the eight most widespread and most virulent Botryosphaeriaceae were tested for their ability to produce phytotoxic metabolites. The chromatographic profiles of their culture filtrates organic extracts showed the ability of all isolates to produce several and different metabolites. When tested on grapevine leaves and tomato cuttings the organic extracts phytotoxicity varied among isolates and species. To our knowledge, this is the first study on phytotoxic compounds produced by Botryosphaeriaceae species found in Australian vineyards. The phytotoxic metabolites produced by Diplodia seriata, Diplodia mutila, Neofusicoccum australe and, for the first time, by Neofusicoccum luteum were isolated and chemically identified essentially by spectroscopic methods.

     

ZnO–Bentonite nanocomposite: an efficient catalyst for discharge of dyes,phenol and Cr(VI) from water

The present work focused on application of ZnO-NPs@bentonite, as a catalyst, for disposal of different pollutants such as dyes, phenol compounds and Cr(VI) ions from water. The prepared ZnO–bentonite nanocomposite was characterized by using FT-IR, X-ray powder diffraction, and Scanning electron microscopy analysis. The results showed that the amount of zinc oxide influenced the catalytic performance of ZnO–bentonite nanocomposite. Small amounts of zinc oxide on bentonite have a positive effect whereas increase in weight ratios has a negative effect.

     

Two new triterpenoids from Gardenia jasminoides fruits

A new cycloartane triterpenoid, named gardenolic acid C (1), a new ursane triterpenoid, named 3β,16β,21β,23,24-pentahydroxy urs-12,18,20-trien-28-oic acid γ-lactone (2), together with three know triterpenoids, gardenolic acid A (3), gardenolic acid B (4), and 3α,16β,23,24-tetrahydroxy-28-nor-ursane-12,17,19,21-tetraen (5) were isolated from the fruits of Gardenia jasminoides Ellis. The structures of these compounds were elucidated by analyses of spectroscopic data. All isolates were evaluated for their neuroprotective effects in vitro.

     

Susceptibly of Alphitobius diaperinus to Beauveria bassiana extracts

Alphitobius diaperinus is an important pathogen with worldwide distribution that causes severe economic loss of efficiency in broilers. This study evaluates the potential of organic extracts of two strains entomopathogenic fungus Beauveria bassiana (CG71 and UNI40) as a biocontrol agent on A. diaperinus and promotes the phytochemical investigation. The effective percentages of mortalities were 95.97% (UNI40 methanolic extract), 69.23, 64.64, and 50.39% (CG 71 methanolic, ethyl acetate and butanol extracts). However, there was a decrease in the lesser mealworms susceptibility in relation to the use of insecticides and extracts. The metabolites 5-hydroxymethyl-2-furanoic acid, dipicolinic acid and monomethyl dipicolinate were isolated from ethyl acetate extract, and β-adenosine of butanolic extract of B. bassiana CG 71. In addition, the cyclodepsipeptides were identified in methanolic extracts of the two strains. The insecticide activity results indicated that the B. bassiana extracts are an alternative to A. diaperinus control.

     

A hydroxyquinoline-appended ruthenium(II)-polypyridyl complex that induces and stabilizes G-quadruplex DNA

A polypyridyl ruthenium(II) complex with hydroxyquinoline-derived ligand has been synthesized and characterized. The ability to act as telomeric quadruplex inducer and stabilizer, and quadruplex-binding properties of the complex have been evaluated by absorption and emission analyses, fluorescent intercalator displacement (FID) titrations, circular dichroism (CD) spectroscopy, polymerase chain reaction (PCR) stop assay, color reaction studies, fluorescence resonance energy transfer (FRET) melting assay, Job plot, and molecular modeling. Observations revealed that the complex could well induce and stabilize the formation of antiparallel G-quadruplex of telomeric DNA in the presence or absence of metal cations, and showed superior G-quadruplex selectivity over duplex DNA with remarkable ΔT_m value of 18.0?°C even at 50-fold excessive supplies of calf thymus (ct) DNA. The complex exhibited high interaction affinity of 2.56?×?10⁶ M^?1 with G-quadruplex DNA and evident luminescence enhancements of 3.1 and 4.2 times for quadruplex binding in Na⁺ and K⁺ buffer, respectively. In addition, the 1:1 [quadruplex]/[complex] binding mode ratio was determined. The results suggest that the complex can be developed as potential anticancer reagent through binding and stabilization of G-quadruplex DNA.

     

Photocatalytic properties and luminescent sensing of a new 2D layer coordination polymer

A 2D coordination polymer [Zn2(betc)(bip)2]·3H2O (1) has been synthesised by deploying mixed ligand strategy . The photoluminescence properties of 1 in different solvents have been investigated and its sensing properties to detect nitroaromatic compounds (NACs) have been explored. 1 displayed selective sensing for 4- nitrotoluene (4-NT) with lower limit of detection (LOD) 0.62 ppm. The probable mechanism for sensing of NACs by 1 ha s been addressed using quantum chemical calculations. Also photocatalytic properties of 1 to photo-decompose model aromatic dyes viz. methyl violet (MV) and 20 rhodamine B (Rh B) have been evaluated. The experiments indicated that 1 displayed better photocatalytic performance in photo-degrading MV than Rh B. The plausible mechanism through which 1 displayed photocatalytic degradation of aromatic dyes had been revealed using density of states (DOS) and partial DOS calculations.

The probable mechanism for the photocatalytic property and emission quenching of 1 has been proposed with the aid of density of states and partial density of states calculations.     

Microbial transformation of isocoronarin D by Cunninghamella echinulata NRRL 1386

The diterpene isocoronarin D (1) is a bioactive major constituent of labdane diterpene from the aerial parts of Curcuma comosa Roxb. (Zingiberaceae), the Thai medicinal plant. Microbial transformation of 1 was performed by the fungus Cunninghamella echinulata NRRL 1386 to yield three new metabolites, 3β-hydroxyisocoronarin D (2), 6α-hydroxyisocoronarin D (3) and 3β,7α-dihydroxyisocoronarin D (4). The structures of the new compounds were elucidated by spectroscopic techniques.

     

GC-MS and LC-MS Identification of the Phenolic Compounds Present in the ethyl Acetate Fraction Obtained from Senna tora,L. Roxb. seeds

The aim of this work is to characterize the active constituents present in the ethyl acetate fraction of Senna tora, L. Roxb. seeds. Due to the fact that the main biological activity of S. tora, L seeds is attributed to its phenolic compounds which are mainly isolated from Ethyl acetate fraction, to avoid repetition of work and to save time, it was deemed necessary to confirm the identity of these phenolic compounds. This was done by GC-MS and LC-MS analysis of the ethyl acetate fraction where the structures of the isolated compounds were established on the basis of molecular ion peak and their fragmentation pattern. They were identified as Chrysophanol, Chrysarobin, 10-hydroxy-5-methoxy-2-methyl-1, 4-anthracenedione, Rubrofusarin, Parietin, Griseoxanthone-B, Isotorachrysone, and Cumbiasin B.

     

Crystallographic and DFT studies on host-guest complexes consisting of zinc bisporphyrinates and 1-phenylethylamine

We have investigated the chirality transfer from 1-phenylethylamine to a 5-amino-1,3-phthalic acid diamide-linked zinc bisporphyrinate through crystallographic and DFT studies. When the hosts were mixed with optically pure 1-phenylethylamine, CD showed moderate signals in the Soret band region. Single crystals of the corresponding 1:1 and 1:2 host-guest complexes were obtained. We present the first crystallographic structure of a 1:2 host-guest complex consisting of a bisporphyrin host and chiral monoamine guests. The structure reveals that the host-guest interactions are different for two guest molecules. The first guest is involved in a hydrogen bond and π-π interactions, while the second one is only involved in π-π interactions, which has not been observed in previous studies. The corresponding chirality transfer mechanism was also rationalized by DFT calculations.