Effective ultrasound-assisted removal of heavy metal ions As(III), Hg(II), and Pb(II) from aqueous solution by new MgO/CuO and MgO/MnO<Subscript>2</Subscript> nanocomposites

A series of new (MgO) _x CuO and (MgO) _x MnO₂ nanocomposites were prepared and used as adsorbent for removal of As³⁺, Hg²⁺, and Pb²⁺ ions from aqueous solution with high capacity and detection limit. These nanocomposites were synthesized with different molar ratios by sonochemical method in alkaline solution using polyvinylpyrrolidone as a capping agent and were characterized by FTIR, AAS, UV–Vis spectroscopy, and TEM and SEM imaging. The maximum heavy metal ions adsorption was achieved for (MgO)_0.32CuO and (MgO)_2.9MnO₂ nanocomposites assisted by 3-min sonication using ultrasound. Adsorbent capacity of (MgO)_0.32CuO reached 500.0 mg/g and detection limit was 0.1 ppb for As³⁺. Also (MgO)_2.9MnO₂ nanocomposite adsorbed 457.1 mg/g of Hg²⁺ and 461.2 mg/g of Pb²⁺. Extremely low detection limits of 1.5 and 2.0 ppb were obtained for Hg(II) and Pb(II) ions, respectively, which are much lower than the WHO allowable limits. So, these nanocomposites should be excellent candidate for heavy metal removal with advantage of high capacity, high sensitivity, cost effectiveness and easy preparation.     

[Hydroxy(tosyloxy)iodo]benzene in Organic Synthesis: A Facile Synthesis of Furo[3,2-c]coumarins Using α-Tosyloxyketones

Facile synthesis of furo[3,2-c]coumarins (2a–g) via cyclocondensation of 4-hydroxycoumarin and α-tosyloxyketones (1a–g) is described. A plausible mechanism involving C-C bond formation followed by 5-exo-tet cyclization is suggested.     

Directed formation of DNA nanoarrays through orthogonal self-assembly

We describe the synthesis of terpyridine modified DNA strands which selectively form DNA nanotubes through orthogonal hydrogen bonding and metal complexation interactions. The short DNA strands are designed to self-assemble into long duplexes through a sticky-end approach. Addition of weakly binding metals such as Zn(II) and Ni(II) induces the formation of tubular arrays consisting of DNA bundles which are 50-200 nm wide and 2-50 nm high. TEM shows additional long distance ordering of the terpy-DNA complexes into fibers.     

Site specific interaction between ZnO nanoparticles and tryptophan: a first principles quantum mechanical study

First principles density functional theory calculations are performed on tryptophan-ZnO nanoparticles complex in order to study site specific interactions between tryptophan and ZnO. The calculated results find the salt bridge structure involving the -COOH group and ZnO cluster to be energetically more favorable than other interacting sites, such as indole and amine groups in tryptophan. The interaction between tryptophan and ZnO appears to be mediated by both ionic and hydrogen bonds. The calculated molecular orbital energy levels and charge distributions suggest non-radiative energy transfer from an excited state of tryptophan to states associated with ZnO, which may lead to a reduction in the emission intensity assigned to the π-π* transition of the indole functional group of tryptophan.     

Herbicidal activity of culture filtrates of Trichoderma spp. against two problematic weeds of wheat

The herbicidal potential of culture filtrates of four Trichoderma spp., namely Trichoderma harzianum Rifai, Trichoderma pseudokoningii Rifai, Trichoderma reesei Simmons and Trichoderma viride Pers., was evaluated against two problematic weeds of wheat, Phalaris minor L. and Rumex dentatus L. In laboratory bioassays, generally, metabolites of all four Trichoderma species significantly reduced various root and shoot growth parameters of the two target weed species. The original concentrations of the culture filtrates of all Trichoderma spp., except T. harzianum, significantly reduced various parameters of root and shoot growth of wheat seedlings. In a foliar spray bioassay, the culture filtrates of all four Trichoderma spp. significantly diminished root and shoot biomass of R. dentatus. The effect of these filtrates on the shoot growth of P. minor and wheat was not significant. Culture filtrates of the four Trichoderma species were successively extracted with butanol, n-hexane, chloroform and ethyl acetate. In detached leaf injection bioassays, n-hexane fractions (3 mg mL(-1)) of T. pseudokoningii, T. reesei and T. viride, and ethyl acetate fractions of T. horzianum and T. pseudokoningii were found to be toxic against R. dentatus. This study concludes that the culture filtrates of Trichoderma species have herbicidal potential in the control of R. dentatus.     

Antioxidant activity of some lichen metabolites

Antioxidant activity of several classes of lichen metabolites were assessed in the in vitro superoxide radical (SOR), nitric oxide radical and 2,2-diphenyl-1-picrylhydrazil radical scavenging assays. The despsides sekikaic acid and lecanoric acid showed promising antioxidant activity in SOR assay with IC?? values of 82.0?±?0.3?μmol and 91.5?±?2.1?μmol, respectively, while the depsidone lobaric acid exhibited an IC?? value of 97.9?±?1.6?μmol, all relative to the standard, propyl gallate (IC???=?106.0?±?1.7?μmol). One of the most abundant mononuclear phenolic compounds, methyl-β-orcinol carboxylate was found to be a potent NO scavenger (IC???=?84.7?± 0.1?μmol), compared to the standard rutin (IC???=?86.8?±?1.9?μmol).     

Two new alkylanacardic acids, ozorcardic A and B, from Ozoroa pulcherrima

Two new alkylanacardic acids, ozorcardic A (1) and B (2), along with the known and related metabolite anacardic acid (3), were isolated from Ozoroa pulcherrima. The structures of the new compounds were elucidated by detailed spectroscopic and spectrometric analysis.     

Effect of inclusion complex on nitrous acid reaction with flavonoids

The kinetic of the nitrous acid reactions with quercetin and catechin has been studied using spectrophotometric method in aqueous solution. The results show that these antioxidants participate in oxidation reactions with nitrous acid which is derived from protonation of nitrite ion in mild acidic conditions. Corresponding o-quinones as relatively stable products were detected by spectrophotometric techniques. pH dependence of the reactions has been examined and the rate constants of reactions were obtained by non-linear fitting of kinetic profiles. The effect of β-cyclodextrin on the oxidation pathway was another object of this study. It is shown that β-cyclodextrin has an inhibitory effect on the oxidation reaction. The rate constants of oxidation reactions for complexed forms and their stability constants were obtained based on changes in the reaction rates as a function of β-cyclodextrin concentration.     

Interplay between two spin states determines the hydroxylation catalyzed by P450 monooxygenase from Trichoderma brevicompactum

Tri11 (now renamed as tri22) encoded cytochrome P₄₅₀ monooxygenase in Trichoderma brevicompactum catalyzes the C-4 C-H hydroxylation of 12, 13-epoxytrichothec-9-ene (EPT) to produce trichodermol in the biosynthetic pathway of trichodermin/harzianum A. The density functional theory (DFT)-quantum mechanics (QM) approach is applied to elucidate the hydroxylation of EPT by using a model active species of P₄₅₀ (Cpd I). The QM calculations were performed on the active site complex, to find out transition-state structure, intermediate, and product complexes for the two spin states at different potential energy surfaces. The two state reactivity rebound-free product formation resulted from the interplay of two spin states (doublet and quartet).     

Recent trends in the synthesis of 1,2,3-thiadiazoles

Abstract

1,2,3-Thiadiazoles, structurally active pharmacophores have attracted significant attention of synthetic chemists, medicinal and pharmaceutical researchers because of their versatile biological activities against various diseases such as herbicidal, insecticidal, antiviral, antitumor, antimicrobial, anticancer, plants activator and anti-amoebic activities. A literature survey of the last decade presented in this review article summarizes the major synthetic approaches, methodologies and strategies adopted for the synthesis of 1,2,3-thiadiazole scaffolds which will be help for medicinal chemists and pharmacists in future synthesis and development of novel therapeutic agents.