Tài liệu miễn phí Hoá học
Download Tài liệu học tập miễn phí Hoá học
Synthesis, in vitro DNA interactions, cytotoxicities, antioxidative activities, and topoisomerase inhibition potentials of Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) complexes with azo-oxime ligands
Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) transition metal complexes of 2-hydroxy-5-[(E)-(4-phenyl) diazenyl] benzaldehyde oxime and 2-hydroxy-5-[(E)-(4-nitrophenyl) diazenyl] benzaldehyde oxime ligands were synthesized and characterized through NMR, IR, ESI mass, and UV analysis. DNA binding abilities of the complexes were revealed using a UV-Vis spectrophotometer with the absorption titration and competitive binding techniques. Hydrolytic and oxidative DNA cleavage activities under different conditions were also proved. Topoisomerase I inhibition efficiencies and in vitro free radical scavenging activities of all complexes were examined. Finally, the selective cytotoxic potentials of all complexes were evaluated in human colon cancer, normal colon, and fibroblast cell lines using the water-soluble tetrazolium salt (WST-1) assay.
4/3/2023 10:00:24 PM +00:00
Experimental and computational studies on the absorption properties of novel formazan derivatives
Eight novel 3-(4-(benzyloxy)phenyl)-5-(4-bromophenyl)-1-(4-substituted-phenyl)formazan (4a–4h) were synthesized by coupling of substituted phenylhydrazones with diazonium salts of 4-bromoaniline. The substituted phenylhydrazones, which are intermediate products, were obtained from the condensation of substituted phenylhydrazines with 4-(benzyloxy)benzaldehyde. All target compounds were characterized by using FTIR, 1 H NMR, 13 C NMR, LC−MS spectrometry, and elemental analysis. Absorption spectra of these compounds in solvents with different polarities were investigated thoroughly. Time-dependent density functional theory (TD-DFT) studies were conducted to shed light on their electronic structures, Kohn–Sham orbitals, and electronic transitions.
4/3/2023 9:59:57 PM +00:00
Nanocomposite copper metal as an efficient heterogeneous catalyst in click synthesis of 1,2,3-triazoles in aqueous media
Copper/periodic mesoporous organosilica (Cu/PMO) nanocomposites provided a highly active, reusable, globular, solid-phase catalyst for click chemistry. The reaction proceeds by mixing organohalides, sodium azide, alkyne, and the catalyst in an aqueous medium to afford the desired products. The cost efficiency and recyclability of the catalyst up to six runs without appreciable loss of activity and high yields of products make this procedure greener.
4/3/2023 9:59:19 PM +00:00
Synthesis and MAO inhibitory activity of novel thiazole-hydrazones
A series of new thiazole-hydrazones (3a–3n) were synthesized, characterized, and screened for their hMAOA and hMAO-B inhibitory activity by an in vitro fluorometric method. Selectivity indexes (SIs) were expressed as IC50 (MAO-A) / IC50 (MAO-B). Compound 3f showed promising hMAO-A inhibition with an IC50 value of 1.20 µM and displayed a very significant SI of 0.04 towards hMAO-A. The mechanism of hMAO-A inhibition was investigated by enzyme kinetics using Lineweaver–Burk graphics. Compound 3f was further screened for its cytotoxicity by using a healthy NIH/3T3 mouse embryonic fibroblast cell line (ATCC CRL1658) and was evaluated as nontoxic at its effective concentration against hMAO-A.
4/3/2023 9:59:11 PM +00:00
Synthesis and antinociceptive activities of some novel benzimidazole-piperidine derivatives
In this study, a series of benzimidazole-piperidine derivatives were synthesized with the objective of developing potent antinociceptive agents. Some 2-(4-substituted-phenyl)-1-[2-(piperidin-1-yl)ethyl]-1H-benzimidazole derivatives were obtained by microwave-supported reaction of an appropriate 2-(4-substituted-phenyl)-1H-benzimidazole with 2-(piperidine-1-yl)ethyl chloride. The chemical structures of the compounds were elucidated by FT-IR, 1H NMR, 13C NMR, and HRMS spectral data. Antinociceptive activity was assessed by conducting hot-plate, paw-pressure, and formalin tests. Morphine (5 mg/kg, i.p) was used as a reference drug.
4/3/2023 9:59:01 PM +00:00
Novel bis(aminoalcohol)oxalamide organogelators and their diglycolylamide analogs: Evaluation of gelation efficiency in various organic fluids
Three modular types of bis(aminoalcohol)oxalamides (1, 4, and 7) and bis(aminoalcohol)diglycolylamide (8) gelators have been prepared by the reaction of the respective aminoalcohols with oxalyl and digycolyl methylesters as potential low-molecular-weight organogelators. The gelation properties of these amides have been evaluated in various aromatic organic solvents (xylene, toluene, isopropyl benzene, and aromatic ether type organic fluids such as anisole or α-phenylethylmethylether) as well as the long-chain aliphatic alcohols (1-hexanol, 1-octanol, 2-octanol, and aromatic 1- phenylethanol). The compounds with sec-butyl and ethyl side chains produce good gelation properties in both aromatic and other organic fluids.
4/3/2023 9:58:53 PM +00:00
Photoemissive polymer composite based on new Y(III), Gd(III), and Tb(III) complexes with N-hydroxyphthalimide
In the present work, a green emitting composite with attractive photoluminescent properties was obtained through the embedding of the Tb3+ complex with N-hydroxyphthalimide in a poly-(N-vinyl-pyrrolidone) matrix, which was further processed in thin or thick films. First, several complexes of Gd3+, Tb3+, and Y3+ with N-hydroxyphthalimide with the general formula [M(NHF)3(DMF)2] were prepared at a 1:3 metal/ligand ratio. The Tb3+ complex presents specific emission peaks, with the most intense peak located at 543 nm, thus being selected for incorporation in the poly(N-vinyl-pyrrolidone) matrix.
4/3/2023 9:58:39 PM +00:00
Synthesis of phosphorus-containing polyurethanes and poly(urethane-acrylate)s
Solvent-based polyurethanes and poly(urethane-acrylate)s were synthesized using phosphorus-containing polyester polyols in order to compare the thermal properties of different polymer types. Since the location of the phosphorus group might have vital importance when comparing the thermal properties, phosphorus groups were kept on the pendant chains in poly(urethane-acrylate)s using phosphorus-containing urethane macromonomers while they were kept on the backbone in polyurethanes. The effect of molar mass of polyurethanes and pendant urethane chains of poly(urethane-acrylate)s on thermal properties was also investigated. Characterization of the synthesized polymers was carried out using FT-IR, GPC, NMR, and DSC followed by evaluation of the thermal properties.
4/3/2023 9:58:30 PM +00:00
A new method for simultaneous determination of trace amounts of Cu(II) and Ni(II) ions by preconcentration and spectrophotometric analysis
Immediate preconcentration and spectrophotometric methods have been developed for the determination of trace amounts of cupric ion (Cu(II)) and nickel ion (Ni(II)) through a solid phase extraction with XAD-4-N,N’-bis- (salicylidene) cyclohexanediamine (XAD-4-SCHD) resin and a complex color reaction of the ions with 2,6-dimethylmorpholine dithiocarbamate (DMMDTC) in Triton X-100 media. A high preconcentration factor of 125 was achieved. The spectrophotometric method was based on the measurements of the absorption of colored chelates of ions complexing with DMMDTC, and the adsorptions of the complex solutions were measured at their maximum absorption peaks at 460 and 328 nm for Cu(II) and Ni(II) ions, respectively.
4/3/2023 9:58:21 PM +00:00
Achieving elusive transformations with organocatalysis: Direct β-carbon activation of saturated carbonyl compounds
Direct β-carbon activation of saturated carbonyl compounds for carrying out fast forward β -functionalization has been one of the most difficult to achieve tasks in catalysis. In the past few years, this challenging issue has attracted considerable attention among the chemical community that has led to fruitful developments to accomplish this elusive transformation. In this short review, we highlight recent developments for direct β-carbon functionalization of saturated carbonyl compounds based on conceptually new methods including oxidative enamine catalysis, N -heterocyclic carbene (NHC)-assisted catalysis, and photoredox catalysis.
4/3/2023 9:58:11 PM +00:00
Ultrasonic activation of the arylation reaction of styrene catalyzed by transition metals
The arylation reaction of styrene was tested in the presence of different transition metal-based catalysts, mainly iron-based, given its low cost and its nonpolluting and nontoxic characteristics. The study of the effect of sonochemical activation on the evolution of the selectivity of the reaction is also proposed. Higher efficiency was observed for a very short period of time of just a few minutes. Furthermore, an improvement of the selectivity of the arylation of the external carbon of styrene was observed.
4/3/2023 9:58:03 PM +00:00
Decolorization of reactive orange 16 via ferrate(VI) oxidation assisted by sonication
The decolorization of azo dye C.I. reactive orange 16 (RO16) via ferrate(VI) and sono-ferrate(VI) methods, which is the combination of the ferrate(VI) oxidation method with sonication, has been achieved in the present study. The influences of some important operating parameters, which are the initial pH, the concentration of potassium ferrate(VI) (K2FeO4) and the RO16 dye, and ultrasonic density (for only the sono-ferrate(VI) method), on the color removal have been investigated. The optimum conditions have been determined as pH = 7 and [K2FeO4] = 50 mg L−1 for the individual ferrate(VI) oxidation method and pH = 7 and [K2FeO4] = 50 mg L−1 by direct sonication at 0.50 W mL−1 ultrasonic density and 20 kHz fixed frequency for the sono-ferrate(VI) method.
4/3/2023 9:57:52 PM +00:00
A rapid, efficient, and green synthesis of benzo[a]chromeno[2,3-c]phenazine derivatives via microwave assistance and DABCO catalyzed a novel domino cyclization
An efficient, convenient, and environmentally benign procedure for the synthesis of novel benzo[a]chromeno[2,3-c]phenazine derivatives has been developed by domino four-component condensation reaction between 2-hydroxynaphthalene-1,4-dione, o−phenylenediamine, aromatic aldehydes, and naphthols or phenol in the presence of a catalytic amount of DABCO as an expedient, ecofriendly, and reusable base catalyst under microwave irradiation in EtOH/H2O (1:1). This green process produces biologically and pharmacologically significant heterocycles in a single one-pot operation and offers considerable advantages such as operational simplicity, short reaction time, high yields, reusability of the catalyst, absence of any tedious workup or purification, and avoidance of hazardous reagents/solvents.
4/3/2023 9:57:44 PM +00:00
Online coupling electrochemical preconcentration and GFAAS technique as effective method for determination of ultratrace concentrations of antimony in groundwater and surface water samples
The present article describes a method of determination of low antimony concentrations using a graphite furnace AAS technique after electrochemical preconcentration. A 2-electrode flow-through cell was developed with a working electrode made of gold-coated porous carbon and an accessory Pt electrode. This cell worked in online coupling with the graphite furnace atomizer. Accumulation occurred from the 6 M hydrochloric acid solution and 2M nitric acid was used to dissolve and transport antimony into the sampling loop. The sampling loop was placed on a 6-way valve.
4/3/2023 9:57:37 PM +00:00
Synchrotron X-ray diffraction studies of β-Ca2−xMxSiO4 (M = Mg and Sr)
The structures of Mg- and Sr-doped β-Ca 2SiO4 have been established from high-resolution synchrotron X-ray powder diffraction. These silicates are all isostructural and the structures have been refined in the monoclinic space group, P21/n. As expected based on size arguments, the cell parameters increase as the amount of Sr increases and likewise decrease as the amount of Mg increases due the size effects of the dopant cation. In all cases the SiO4 tetrahedra are essentially regular.
4/3/2023 9:57:23 PM +00:00
The reactions of N3P3Cl6 with monodentate and bidentate ligands: The syntheses and structural characterizations, in vitro antimicrobial activities, and DNA interactions of 4-fluorobenzyl(N/O)spirocyclotriphosphazenes
The Cl replacement reactions of 4-fluorobenzyl(N/O)spirocyclotriphosphazene (2) with excess monoamines led to the formation of 4-fluorobenzylspiro(N/O)tetraaminocyclotriphosphazenes (2a–2d). The partly substituted dispiro 3b and dispiro 3c and fully substituted trispirocyclotriphosphazenes (trans 4a, cis 4c, 4d, and 4e) were obtained, respectively, from the reactions of 2 with one equimolar and two equimolar amounts of diamines, aminoalcohol, and diols. Although efforts were made for the separation of the cis/trans and optical isomers of the dispiro phosphazenes, only one set of diastereomers (RR/RS or SS/SR) of dispiro 3b and dispiro 3c was isolated, respectively.
4/3/2023 9:57:13 PM +00:00
Adsorption isotherm modeling of carbendazim and flumetsulam onto homoionic-montmorillonite clays: Comparison of linear and nonlinear models
This study deals with the adsorption of two pesticides, carbendazim and flumetsulam, from aqueous solutions onto four homoionic-montmorillonite clays (Ag+, Zn2+, Cu 2+, and H+). Equilibrium adsorption isotherm data were analyzed using Freundlich, Dubinin–Radushkevich, and Temkin isotherms. Linear and nonlinear fitting methods were compared to determine the best-fitting isotherms for the experimental data. Three error analysis methods were used to evaluate the data for each method: the coefficient of determination (R2), sum of squared errors (SSE), and chi-square test (χ2). Equilibrium adsorption isotherms exhibited that the carbendazim adsorption mainly involved cation exchange with homoionic-montmorillonite adsorbents.
4/3/2023 9:57:06 PM +00:00
Diastereoselective synthesis of novel 2,5-dioxopyrrolidine derivatives via biocatalytic domino reactions
A series of novel 2,5-dioxopyrrolidines were synthesized by the one-pot reaction of coumarin-3-carboxylic acids 1 with thiourea derivatives and alkyl isocyanides in the presence of Fe 3 O4 NPs @ lipase as heterogeneous reusable nanobiocatalysts with high yields. Multicomponent reactions (MCRs) are useful tools for the efficient synthesis of heterocyclic compounds due to their environmental friendliness, atomic economy, and green specifications.
4/3/2023 9:56:58 PM +00:00
Calix[4]pyrroles with bulky substituents and their anion binding studies
Calix[4]pyrrole derivatives with bulky substituents at their meso-positions were synthesized via mixed condensation of pyrrole with cyclohexanone and acetophenone derivatives. Anion binding studies, carried out by isothermal titration calorimetry in 1,2-dichloroethane with Cl− and CH3CO−2 anions in the form of their tetrabutylammonium salts, revealed that these new calix[4]pyrrole derivatives can bind the aforementioned anions as effectively as the unsubstituted “parent” system, octamethylcalix[4]pyrrole (1). Structural characterizations of new calix[4]pyrroles were carried out by using 1H and 13C NMR spectroscopy corroborated with mass spectrometry.
4/3/2023 9:56:46 PM +00:00
Synthesis of neodymium-iron nanoperovskite for sensing applications of an antiallergic drug
A facile route was used for the fabrication of NdFeO3 (NF) perovskite. The orthorhombic structure of single phase nanocrystalline NdFeO3 perovskite was confirmed by different characterization techniques: XRD, FTIR, TEM, BET, SEM, and EDAX. The nanoperovskite was successfully used as a sensor component with a carbon paste electrode (CpE) for the determination of ketotifen in pharmaceutical formulations. Ketotifen, an antiallergic drug, is utilized for the treatment of asthma attacks, rhinitis, skin allergies, and anaphylaxis. Sodium dodecyl sulfate (SDS) was employed in a surface assembly mode to improve the sensitivity of the sensor response.
4/3/2023 9:56:32 PM +00:00
Singlet oxygen generation from poly[4-diacetoxyiodo]styrene and hydrogen peroxide
Treatment of hydrogen peroxide with a polymer-supported hypervalent iodine compound, poly[4-diacetoxyiodo] styrene (PDAIS), generates singlet molecular oxygen ( 1 O2). Singlet oxygen generation was proved by trapping with typical organic compounds such as conjugated dienes, aromatic dienes, and electron-rich alkene. When compared to monomer analogue, the use of PDAIS in peroxidation of substrates gave slightly better yields (45%–96%). Regeneration and reuse of PDAIS showed similar activity. The mechanism underlying generation of singlet oxygen and reaction scope was examined.
4/3/2023 9:56:26 PM +00:00
Genetic diversity of the critically endangered Ferula sinkiangensis K.M.Shen (Apiaceae) and the implications for conservation
Research on the genetic diversity and structures of endangered plant species with small population sizes is a prerequisite for developing reasonable conservation strategies. Ferula sinkiangensis K.M.Shen is a critically endangered herbaceous perennial and monocarpic medical plant growing in semiarid steppe ecosystems with a small population size within the Yili Valley in Xinjiang, China. Unfortunately, the lack of genetic information has limited our ability to initiate effective conservation strategies for the species. In this study, 14 polymorphic microsatellite primers of F. sinkiangensis were developed and characterized using Illumina HiSeq paired-end reads from genomic DNA.
4/3/2023 9:39:00 PM +00:00
Transcriptomic insights into the molecular aspects of salt stress responses in Kandelia candel roots
The mangrove plant Kandelia candel is a type of woody halophyte that grows in tropical and subtropical ocean intertidal zones and exhibits a high salt tolerance. In this study, 61,970 unigenes were obtained from the roots of 60-day-old K. candel seedlings treated with 0 (control), 200, 400, and 600 mM NaCl for 3 days with an N50 of 1510 bp. Moreover, 454, 311, and 2663 genes were differentially expressed under 200, 400, and 600 mM NaCl treatments, respectively. These differentially expressed genes were primarily involved in plant hormone signal transduction, carbohydrate and energy metabolism, amino acid metabolism, stress response, and defense.
4/3/2023 9:38:45 PM +00:00
Botanical characteristics, potential uses, and cultivation possibilities of mustards in Turkey: A review
The mustard species [(Brassica juncea (brown mustard), B. nigra (black mustard), B. rapa syn. B. campestris (field mustard or turnip), and Sinapis alba (white mustard or yellow mustard)] constitute important genetic resources and sources of raw materials to large number of agrobased industries in Turkey and elsewhere. S. alba is usually used as a condiment in dry form. B. nigra is used as a condiment and as vegetable with dietary fibre, vitamin C, and other anticancer compounds. B. juncea is used for oil and as spice. B. rapa is popularly used for biofuel raw material. However, there is poor focus on their breeding and varietal development for industrial purposes like biofuel production etc.
4/3/2023 9:38:26 PM +00:00
Notes on the genus Sauvetrea (Orchidaceae, Maxillariinae), with a description of a new species
The genus Sauvetrea Szlach. (Orchidaceae) was segregated from Maxillaria sensu lato in 2007. It embraces a group of from 10 to nearly 20 species, all initially defined as Maxillaria sect. Trigonae. Sauvetrea can be easily distinguished from closely related Rhetinantha M.A.Blanco by the lip callus. During the revision of the materials stored in AMES we came across specimens collected by Vargas in Peru, which were initially identified by Schweinfurth as Maxillaria brachypetala Schltr. We compared Vargas’s discovery with the protologue of the latter species and other Sauvetrea, but it does not fit the description of any genus representatives known so far. We describe it below as a new species, Sauvetrea schweinfurthiana Szlach. & Lipińska.
4/3/2023 9:38:18 PM +00:00
Russula shanglaensis sp. nov. (Basidiomycota: Russulales), a new species from the mixed coniferous forests in District Shangla, Pakistan
A new species in the genus Russula from the mixed coniferous forest of District Shangla, Khyber Pakhtunkhwa, Pakistan is described and illustrated. Phylogenetic data derived from DNA sequences of nuclear ribosomal internal transcribed spacer (ITS), along with morphological characterizations, indicate the species is novel. Russula shanglaensis sp. nov. is distinct from other known species in subsect. Virescentinae. It is characterized by the convex to slightly depressed grayish pilei that often reflect rusty brown to light purplish spots, with very lightly striated to tuberculate striated margins.
4/3/2023 9:38:09 PM +00:00
Induction of pollen embryo and chromosome doubling in tobacco (Nicotiana tabacum L.)
Anther culture is an effective breeding method for improving desirable traits, since it allows fast achievement of genetically homozygous lines. The present studies were carried out to evaluate the response of flue-cured tobacco anthers for high frequency pollen embryo induction in different culture media, and the effects of colchicine treatment on tobacco chromosome doubling. The results showed that different media caused significant changes in pollen embryo induction, in which the most obvious change was found in B medium with induction rates of 23.28%, 26.64%, and 28.07% for TMK-12 × Jiyan 5, K326 × Shangkang 70, and NC71 × Jingyehuang, respectively. In addition, shoot tips of the haploid aseptic seedlings cultivated from anthers were treated with 4 g/L colchicine for 48 h, and the ploidy levels were then checked by using flow cytometry and the number of chloroplasts in stomatal guard cells.
4/3/2023 9:38:01 PM +00:00
Regulation of antioxidant activity in maize (Zea mays L.) by exogenous application of sulfur under saline conditions
One of the major effects of salt stress is high production of reactive oxygen species that adversely affect essential cellular metabolic pathways. To limit the elevated production of reactive oxygen species, plants stimulate various types of antioxidants. In this study, sulfur was used to induce tolerance against oxidative stress through modulation of the activities of various antioxidants. Two maize genotypes (Agatti 2003 and Pak Afgoi 2003) were subjected to different salinity (25 and 75 mM) and sulfur (40 and 80 mM) treatments and a control treatment. Various antioxidants and oxidative stress determinants in maize organs (leaf, shoot, and root) were studied.
4/3/2023 9:37:43 PM +00:00
Ứng dụng bùn hạt hiếu khí trên mô hình công nghệ (SBR) để xử lý nước thải có tải trọng hữu cơ thấp
Bài báo trình bày kết quả loại bỏ COD, NH4 + -N (nitơ amôn), T-N (tổng nitơ), T-P (tổng phốt pho) của việc ứng dụng bùn hạt hiếu khí trên bể phản ứng theo mẻ SBR để XLNT đô thị tại Hà Nội có tải trọng hữu cơ thấp trong điều kiện phòng thí nghiệm.
4/3/2023 9:01:22 PM +00:00
Tổng hợp vật liệu xúc tác quang WO3/Ag3 VO4 ứng dụng xử lý kháng sinh amoxicillin trong môi trường nước
Nghiên cứu trình bày hoạt tính quang xúc tác của vật liệu WA-x đã được khảo sát thông qua phản ứng phân hủy kháng sinh amoxicillin (AMX) dưới sự chiếu xạ của bức xạ khả kiến. Hiệu suất phân hủy AMX của vật liệu WA-10 đạt 79,86% sau 3 giờ phản ứng. Vật liệu WA-x có hoạt tính quang xúc tác mạnh hơn WO3 và Ag3 VO4 nhờ sự phân tách hiệu quả của cặp điện tử và lỗ trống quang sinh.
4/3/2023 9:01:13 PM +00:00