Search Results (694)

Chitosan is a natural polysaccharide that is mainly obtained from the shell of marine crustaceans including crabs, lobsters, shrimps, etc. Chitosan has been widely used in biomedicine due to its special characteristics of low toxicity, biocompatibility, biodegradation, and low immunogenicity. However, owing to the limited solubility of CS in water, its water-soluble derivatives are preferred for the mentioned applications. Carboxymethyl chitosan (CMC) is one of the water-soluble derivatives of chitosan, which has antibacterial, anticancer, antitumor, antifungal, antioxidant properties, and is used in both drug delivery and enzyme delivery. This material is also utilized in tissue engineering, wound healing, and bioimaging. For these reasons, in this article, a different and novel method by using KI and/or ultrasonication is proposed. Full article

Among the water pollution sources, heavy metals are considered the most hazardous because of their high toxicity to human health and their ability to badly damage the kidneys, brain, and nerves, as well as cause birth defects. Based on the promising features of metal-organic frameworks ( MOFs), they could act as a favorable candidate in heavy metal removal applications. A calcium-based metal-organic framework was synthesized by the deposition method using benzene-1,2,4,5-tetracarboxylate as a linker. After characterization of the MOF was performed using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) analyses, it was applied to efficient adsorption of Pb(II) pollutant ions. The potential of obtained MOF, [Ca(H₂btec)·H₂O]_n, H₂btec: benzene-1,2,4,5-tetracarboxylic acid was investigated by adsorbing Pb(II) ions in an aqueous solution, separating the adsorbent using centrifugation, and finally measuring the residual Pb(II) ions using the ICP-AES method. Full article

The increasing tolerance and resistance of pathogens to conventional antibiotics is a global health issue, and there is a need to use effective and new substances. Metal–organic frameworks (MOFs) are highly functional materials with antimicrobial properties that come from their composition, structure, and high internal volume, which could be a source for antimicrobial guest molecules integrated into the pores. In addition, MOFs can contain more than one type of metal ion in the same structure. In this work, a metal–organic framework, [Ba(H₂btec)·H₂O]_n, was synthesized by the deposition method using benzene-1,2,4,5-tetracarboxylic acid (H4btec) and Ba(NO₃)₂. Characterization of the MOF was performed using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) and x-ray fluorescence (XRF) alyses. The metal–organic framework was used against Gram-positive and Gram-negative bacteria including Keleb peneumonia, Staph coccus aureus, Staph sapropphyticus, and Esherichia coli. Full article

A phenolic compound in Foeniculum vulgare can improve human health. Foeniculum vulgar contains flavonoids, glycosides, and other constituents that are used for medicinal ailments. Trans-anethole, fenchone, and estragole essential oils are the main ingredients in F. vulgare seeds. The principle component of fennel oil, anethole, has structural similarity with the synthetic oestrogen diethylstilbestrol, making it an active estrogenic agent. Women with PCOS may exhibit obesity, amenorrhea, oligomenorrhea, infertility, or androgenic features, which are characterized by the absence of ovulation and hyperandrogenism. Oligomenorrhea is a kind of irregular menstruation period. Treatment of oligomenorrhea depends on the causes; the main cause of oligomenorrhea is the presence of polycystic ovarian syndrome (PCOS), with 75–85%experiencing infrequent periods. This mini-review focuses on F. vulgare seeds as an advantageous addition to treat PCOS. Women with PCOS also have a lower level of the hormone progesterone due to the absence or reduction in ovulation. Numerous phytoestrogens can be found in F.vulgare seeds; with less insulin resistance and lower blood sugar level, fennel phytoestrogen content is beneficial. It is also thought to aid in reducing the cellularim balance that causes PCOS’s metabolic abnormalities. Full article

Aminobenzoic acid derivatives have shown various pharmacological properties, one of which is pesticide activity, giving these compounds the ability to work as alternatives to current pesticides. Nanotechnology could efficiently support the use of these compounds by encapsulating them in stable nanoformulations to improve their stability and effectiveness. In the present work, 3-chloropropylaminobenzoate derivatives were synthesised and evaluated against their effect on the viability of the insect cell line Sf9 (Spodoptera frugiperda), and nanoencapsulation studies of the most active compound were carried out. The most potent molecules reduced insect cell viability by around 40% at 100 µg/mL. Full article

There exist a number of classical methods for the synthesis of substituted pyrazines. Among this variety of reactions, the synthesis of substituted pyrazines from nitriles does not stand out in either the number of known examples or in product yield. However, the one-stage character of the transformation, together with the uncertainty of its mechanism, aroused our interest in this catalytic reaction. Here, we report the successful implementation of the Cp₂TiCl₂-catalyzed reaction of aliphatic nitriles with EtAlCl₂ and Mg, which led to the selective preparation of 2,3,5,6-tetraalkyl-substituted pyrazines, 2,4,5-trisubstituted-1H-imidazole or 2-aminocyclopent-1-ene-carbonitrile depending on reaction conditions and substituents. Full article

The results of my research in the fields of theoretical studies and computer modeling of supramolecular chemical systems were presented. The main attention was focused on theoretical studies in the following topics: cycloaddition and nucleophilic addition reactions involving substrates with multiple CC and CN bonds, their mechanisms, driving forces, kinetics and thermodynamics; the consideration of the catalysis of hydrocarbons oxidation processes and their conversion to alcohols, ethers, aldehydes, ketones and carboxylic acids; investigations of various unusual types of non-covalent interactions (from quite trivial hydrogen bonds to more exotic σ-hole, π-hole and metallophilic interactions) in organic, organometallic and coordination compounds. Some fundamental issues of supramolecular chemical systems were also discussed (e.g., structure and properties of chemical compounds and their supramolecular associates; conformational transitions and rotation barriers of functional groups; nature of chemical bonds; orbital and charge factors; photophysical properties). Full article

Two fluorescent sterol-like molecules have been synthesized, namely, a derivative of 7-nitrobenzofurazan (NBD) with 17-(methylamino)-androst-5-en-3beta-ol (DAM-NBD) and NBD-piperazine conjugate with cholesteryl chloroformate (NBD-pip-CCF). In silico docking and plasma membrane simulations have shown ability of the compounds to penetrate the lipid bilayer, as well as to bind affinely of the yellow fever mosquito SCP-2 protein structure (code PDB: 3BDQ; binding energy about −11.9 kcal/mol). Also docking with AlphaFOLD-predicted insect Neverland protein structure demonstrated DAM-NBD binding with a similar affinity. The theoretical results indicate perspectives of the fluorescent steroid usage to study insect protein-sterol interactions. Full article

The reductive cyclization of different organic nitro compounds by carbon monoxide, catalyzed by transition metal complexes, is a very efficient and clean strategy for the synthesis of many N-heterocycles. However, it requires the use of autoclaves and pressurized CO lines. In this paper, the authors will present the results obtained in their laboratories on the use of phenyl formate as a convenient CO surrogate, able to liberate carbon monoxide under reaction conditions and allowing for the use of a cheap glass pressure tube as a reaction vessel. In most cases, yields were better than those previously reported using pressurized CO, proving that the use of CO surrogates can be a viable alternative to the gaseous reagent. Full article

The data obtained by the authors in the field of chemistry of substituted borolanes and 2,3-dihydro-1H-boroles are summarized. The authors developed a selective method for the synthesis of five-membered boracarbocycles via transmetalation of aluminacarbocycles, obtained by the catalytic cycloalumination of unsaturated compounds (terminal olefins or acetylenes) with AlEt₃ in the presence of Cp₂ZrCl₂ as a catalyst by boron halides (BF₃·Et₂O, BCl₃, and BBr₃). Some examples of the use of this approach to modify steroid compounds (in particular, to introduce a borolan fragment into them) are described in this review. Full article

We have previously obtained significant results in the cycloalumination of olefins with EtAlCl₂ in the presence of magnesium and a Cp₂ZrCl₂ or Cp₂TiCl₂ catalyst. Here we report the development of an efficient one-pot catalytic method for the synthesis of tertiary alcohols from AlCl₃, aryl olefins, and ketones under the action of Cp₂TiCl₂. The developed method for producing tertiary alcohols has a general character and allows the conversion of styrene and substituted styrenes (ortho-, para-methylstyrenes) into aryl-substituted tertiary alcohols with yields of up to 76% in the reaction with acetone or methyl ethyl ketone. We assume that the reaction proceeds through the formation of a titanacyclopropane intermediate. Full article

The preparation of enoxaparin via the base-promoted depolymerization of heparin is well known. In this paper, we present our efforts to convert this preparation into a flow method. Streams of base and ester solutions are combined and heated in a flow reactor, and the variations in flow rate, temperature, and residence time were examined. NMR analysis demonstrated that careful control of the reaction parameters affords enoxaparin-like materials. An analysis was carried out by NMR spectroscopy and the optimum conditions were determined. Full article

Lanthanide (Ln(III)) luminescent complexes have been attracting interest for technological applications and molecular imaging. The luminescence of Ln(III)) ions is weak and depends on the use of light absorbing coordination ligands which sensitizes the lanthanide ion. A large variety of coordination ligands has been screened such as dipicolinates, oligo-pyridines, cyclen and crown ether derivatives, porphyrins, cryptands or calixarenes. In our research group we have developed an expeditious methodology to prepare bis(oxazolyl)pyridine ligands for LnIII from threonine and 2,6-pyridinedicarbonyl dichloride. In this work, two new pyridine-bis-oxazolyl ligands with an aromatic ring in position 5 of the oxazole ring were prepared from phenyl-serine and 2,6-pyridinedicarbonyl dichloride. The photophysical properties of compounds 1 and 2 were studied in acetonitrile and in Tris-HCl buffer (0.1 M, pH 7.1). These compounds were used for complexation with Eu(III) and/or Tb(III) ions and the photophysical properties of the complexes studied. Luminescence titrations with anhydrous EuCl₃ and TbCl₃ allowed the determination of the stoichiometry of the complexes and of the stability constants. Full article

This work investigates the inclusion of the nimesulide molecule into the beta- and gamma- cyclodextrin cavity and explores the application of molecular modelling for the purposes of proving the host-guest complexation process. The author’s experimental method is based upon the basic methods of obtaining inclusion complexes. A combination of physical and chemical methods was utilized in order to analyze the compounds obtained qualitatively and quantitatively. In addition, it was decided that the focus will be on figuring out the possibility applying computer modeling. The characteristics of the molecular systems under study were calculated using the «Gaussian 09W» software package (Revision version 16 A.03). The functionality of this software package allowed us to apply both the restricted Hartree–Fock (RHF) method, and the hybrid density functional method-B3LYP. The 6–31 G split-valence basis set was utilized for all subsequent calculations, to quantify the influence of the additional polarization and diffuse functions on the calculations. Using computational chemistry, the structures of γ-, β-cyclodextrin, nimesulide, and surface complex compounds were constructed and optimized. The possible structures of nimesulide inclusion complexes with β-, γ-cyclodextrin were also designed. The results obtained will influence the evaluation of the possibility of obtaining the clathrate complex. The crystal structure of the nimesulide inclusion complex obtained by us with γ-cyclodextrin was experimentally confirmed by X-ray diffraction analysis. To date, not many works are known to utilize these molecular modeling techniques in the field of supramolecular chemistry based on an independently synthesized inclusion complex. Full article

The crystal structures of mononuclear cyclopalladated compounds with phosphine ligands are investigated. The reactions of the five-membered cyclopalladated dinuclear complexes [Pd(L)(µ-Cl)]₂ with the monophosphine ligand (PPh₃) and diphosphine ligand (dppm) in the molar ratio of 1:2, and ammonium hexafluoride in the case of compound b, result in the mononuclear complexes [Pd{2,3,4-(CHO)C₆H₃C(H)=NCy}{PPh₃}[Cl] (1a) and [Pd{2,3,4-(CHO)C₆H₃C(H)=NCy}{Ph₂PCH₂PPh₂-P,P}][PF6] (1b). Full article