Use Of Pyridine Research Articles

Ecological and physiological as well as biochemical properties of representatives of the Genus sedum L.

The article deals with the history of the study and the current state of research of physiological and biochemical properties of the plant genus Sedum that are useful for human and has been used in folk medicine for many years. It was noticed that antioxidant properties of extracts from plants S. sarmentosum, S. sempervivoides, S. takesimense were caused by the presence of phenolic compounds. Methanol extract of plants S. takesimense exhibited strong scavenging activities against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radicals as well as significant inhibitory effects on lipid peroxidation and low density lipoprotein (LDL) oxidation induced by a metal ion Cu2+. Various immunomodulatory activities of various fractions of plants extracts (S. dendroideum, S. kamtschaticum, S. sarmentosum, S. telephium) are observed. It was shown that the ethanol extract of S. sarmentosum and it’s fractions suppressed specific antibody and cellular responses to ovalbumin in mice. The methanol extract of plants S. sarmentosum reduced the levels of anti-inflammatory markers, such as volume of exudates, number of polymorphonuclear leukocytes, suppressed nitric oxide synthesis in activated macrophages via suppressed induction of inducible nitric oxide synthase (iNOS). Polysaccharides fractions from plants S. telephium inducing productions of tumor necrosis factor alpha (TNF-α), increasing the intensity of phagocytosis in vitro and in vivo. Methanol extract from the whole part of S. kamtschaticum strongly inhibit PGE2 production from lipopolysaccharide-induced RAW 264.7 cells, a mouse macrophage cell line via modulating activity in gene expression of the enzyme cyclooxygenase-2 (COX-2). The methanol extract of plants S. sarmentosum and the major kaempferol glycosides from S. dendroideum have antinociceptive activity. It was noticed that anti-adipogenic activity of extracts from plants S. kamtschaticum were caused by inhibition of peroxisome-proliferator-activated receptor γ (PPARγ) expression and it’s dependent target genes, such as genes encoding adipocyte protein 2 (аР2), lipoprotein lipase (LPL), adiponectin and CD36. Polysaccharides fractions from S. telephium cause inhibition of cell adhesion of human fibroblast (MRC5) to laminin and fibronectin via interfere with integrin-mediated cell behaviour and they contributed to the role of polysaccharides in cell-matrix interaction. The methanol extract of plants S. sarmentosum exhibited a significant inhibitory activity in the chick embryo chorioallantoic membrane angiogenesis in a dose-dependent manner. The crude alkaloid fraction of S. sarmentosum caused a dose-dependent inhibition of cell proliferation on murine hepatoma cell line BNL CL.2 and human hepatoma cell line HepG2 without necrosis or apoptosis. Alkaloids from plants S. sarmentosum may improve survival of hepatoma patients via the inhibition of excessive growth of tumor cells. Plant’s juices have antiviral activity (S. sarmentosum, S. spurium, S. stahlii). Crude ethanol extract S. praealtum have spermicidal activity of the in mice and a relevant inhibitory effect of aqueous extract on human spermatozoa motility as well as an anti-fertilizing activity in rats. Hepatoprotective triterpenes, e.g., δ-amyrone, 3-epi-δ-amyrin, δ-amyrin and sarmentolin were isolated from S. sarmentosum. 2- and 2,6-substituted piperidine alkaloids (e.g., norsedamine, allosedridine, sedamine, allosedamine) are observed in plants S. acre, which in the presence of data on the use of pyridine and piperidine derivatives for treating neurodegenerative diseases (e.g., Alzheimer's disease), points on the promising research in this area. Taking into account that biologically active compounds are accumulated in the aboveground vegetative organs of plants of Sedum, the prospects of further study of the use of Sedum for the purposes of biotechnology and in the pharmaceutical industry becomes apparent. This work extends the existing views regarding the use of plants Sedum.

Influence of additives in bulk heterojunction solar cells using magnesium tetraethynylporphyrin with triisopropylsilyl and anthryl substituents

We designed and synthesized anthryl-disubstituted magnesium tetraethynylporphyrin([{5,15-bis(anthracen-9′-yl)ethynyl}-10,20-bis{(triisopropylsilyl)ethynyl}porphyrinato] magnesium(II)), and applied it as an electron donor to solution-processed bulk heterojunction small molecule organic solar cells. The compound was characterized by single crystal X-ray crystallography as well as UV-vis light absorption spectrum showing the absorption maximum and onset at 700 and 740 nm, respectively. Organic solar cells using this compound and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as electron donor and acceptor, respectively, showed power conversion efficiency of 1.31% at the donor and acceptor ratio of 1:3. The use of pyridine as a coordinating additive increased power conversion efficiency to 1.61%, which was the best among tested additives, THF, pyradine, dioxane, and 1,8-diiodooctane.

Exciton Dynamics in Hybrid Polymer/QD Blends

The prospect of exploiting quantum dots (QDs) properties (tunable absorption spectrum, multiple exciton generation) while maintaining the flexible structure of polymer systems opens new possibilities in the photovoltaic field. Although charge transport dynamics in pristine polymer and QDs systems have been quite well established lately, a complete understanding of the charge transfer process between QDs and polymers when they are in blends is still lacking. In this work we used static and ultrafast fluorescence spectroscopy together with Atomic force Microscopy (AFM) to study the exciton dynamics in polymer/QDs films. Specifically we used poly(3-hexylthiophene) (P3HT) as the hole conducting donor material and the core shell CdSe(ZnS) QDs as the electron acceptor material. The QDs surface has been treated with two different capping ligands treatments: one based on the use of pyridine and the other one on hexanoic acid. The influence of the two different methods on the exciton dynamics and on the morphology will also be discussed. Blends containing differently treated P3HT/CdSe(ZnS) wt% ratios have been prepared producing films having uniform morphology and good intermixing, as proved by AFM measurements. Ultrafast fluorescence decays allowed us to compare the exciton dynamics in the polymer pristine respect to the treated P3HT/CdSe(ZnS) films. Efficient fluorescence quenching has been shown by both kind of blends respect to the pure polymer.

Novel experimental model of non-infectious pharyngitis in rats

IntroductionCurrently, there is a paucity of scientific literature and reports related to screening models for non-infectious type of pharyngitis. In this context, we made a sincere attempt to establish a novel animal model for screening drugs against non-infectious pharyngitis in rats. We have considered the use of pyridine, croton oil and their combination for inducing non-infectious pharyngitis in rats. MethodsVarious concentrations of pyridine were applied topically to the pharyngeal region of rats and the extent of inflammation was assessed by Evans Blue (EB) dye exudation test, evaluating the serum levels of proinflammatory cytokines and histopathology. Dexamethasone and diclofenac were used as reference standards. ResultsUpon pyridine application (2.5%, 5%, 10%, 20%, 40% and 80% in saline), dose-dependent increase in EB dye extravasation was observed (increased vascular permeability). In addition, the levels of TNF-α (P<0.01) and IL-6 (P<0.01) were significantly increased compared to control. Furthermore, the histopathology of pharyngeal tissue showed hypertrophy of submucosal glands, severe inflammation of the pharynx characterised by presence of mononuclear cells, neutrophils along with haemorrhages and congestion; however, normal control animals showed normal cytoarchitecture of pharynx. Indeed, dexamethasone (0.25, 0.5 and 1mg/kg, i.v.) and diclofenac (1, 2.5 and 5mg/kg, i.v.) showed dose-dependent protection against pyridine-induced pharyngitis. Further, the possible mechanism of pyridine-induced pharyngitis is thought to be primarily mediated through phospholipase A2 and cyclooxygenase (COX) pathway. ConclusionThese findings suggest that pyridine-induced pharyngitis is a simple and versatile novel animal model for screening the drugs against non-infectious pharyngitis in rats.

Transition‐Metal‐Free Multicomponent Reactions Involving Arynes, N‐Heterocycles, and Isatins

Mix and match: With isoquinoline as the nucleophilic trigger, multicomponent reactions afforded spirooxazino isoquinoline derivatives, proceeding through 1,4-dipolar intermediates. The use of pyridine as a nucleophile furnished indolin-2-one derivatives, with the reaction likely proceeding through a pyridylidene intermediate.

ChemInform Abstract: HF—Pyridine: A Versatile Promoter for Monoacylation/Sulfonylation of Phenolic Diols and for Direct Conversion of t‐Butyldimethylsilyl Ethers to the Corresponding Acetates.

AbstractThe use of HF—pyridine as a promoter in the acylation of phenolic diols predominantly yields the monoprotected diols, in contrast to the use of pyridine alone which promotes diprotection.

Graphene prepared via a novel pyridine–thermal strategy for capacitive deionization

A novel pyridine–thermal strategy for successive exfoliation and reduction of graphite oxide with the use of pyridine as the intercalating agent and dispersant is reported, and the obtained graphene exhibits a good performance in capacitive deionization.

The oxidation of alcohols with trichloroisocyanuric acid: pyridine from base to organocatalyst

An alcohol oxidation method based on the use of pyridine or 3-cyanopyridine as an organocatalyst in combination with trichloroisocyanuric acid as the terminal oxidant is reported. It is demonstrated that secondary aliphatic alcohols can be selectively oxidized to the corresponding ketones in the presence of primary aliphatic alcohols. The method is also suitable for the oxidation of primary and secondary benzylic alcohols. N-Chloropyridinium cyanurates are proposed as the active alcohol-oxidizing species.

Structural motifs in phenylbismuth heterocyclic carboxylates – secondary interactions leading to oligomers

The reaction of triphenylbismuth [BiPh(3)] with several heterocyclic carboxylic acids was explored. Seven crystalline compounds, [PhBi(2-O(2)C-3-(OH)C(5)H(3)N)(2)(2-O(2)C-3-(OH)C(5)H(3)NH)] (5), [(Bi(2-O(2)C-3-(OH)C(5)H(3)N)(4))(C(5)H(5)NH)(C(5)H(5)N)] (7), [PhBi(2-O(2)C-C(4)H(3)N(2))(2)(2-O(2)C-C(4)H(4)N(2))·H(2)O] (8), [PhBi(2-O(2)C-C(9)H(6)N)(2)·H(2)O] (9), [Ph(2)Bi(O(2)C-C(4)H(3)O)] (10), [Ph(2)Bi(O(2)C-C(4)H(3)S)] (11) and [PhBi(O(2)C-C(4)H(3)S)(2)](2) (12), were prepared by simple reactions using BiPh(3) and the corresponding acids, 3-hydroxypicolinic acid, pyrazine-2-carboxylic acid, quinoline-2-carboxylic (quinaldic) acid, furan-2-carboxylic acid and thiophene-2-carboxylic acid. Compound 5 primarily exhibits a coordination number of six with pentagonal pyramidal geometry at bismuth, but an additional weak Bi···O interaction in the direction of the lone pair of electrons is present. This feature leads to a weakly bound dimer. The use of pyridine as the solvent in a similar reaction, however, led to 7, in which all of the Bi-Ph bonds are cleaved. In this compound, bismuth exhibits a coordination number of eight and distorted dodecahedral geometry. In compound 8, the geometry around bismuth is primarily a pentagonal pyramid, however, clear-cut but weak secondary Bi···N interactions leading to a dimeric formulation are discernible in the structure. The quinaldate compound 9 exhibits a lower formal coordination number of five for bismuth, with square pyramidal geometry, but again two secondary Bi···O interactions for each bismuth in the direction of the lone pair lead to a dimer. A similar secondary Bi···O interaction involving furan oxygen is present in the furoate compound 10, which is a polymeric chain (one dimensional coordination polymer). Although the thiophene carboxylate 11 is also a polymeric chain, no Bi···S interactions are present. Unlike the previously reported tetrameric biscarboxylate [PhBi(2-O(2)C-C(5)H(3)N)(2)](4), the thiophene carboxylate [PhBi(O(2)C-C(4)H(3)S)(2)](2) (12) is a dimer considering only primary interactions. However, these dimers are arranged in such a way that there are secondary Bi···S interactions in the structure in the expected direction of the lone pair of electrons on bismuth. Thus, these studies suggest that the stereochemical activity (or inactivity) of the bismuth lone pair of electrons need to be judged more cautiously. TGA studies are consistent with the presence of Bi-Ph groups in all of the compounds, except 7, as indicated by their formulae.

Dichloro (bis[diphenylthiourea]) cadmium complex as a precursor for HDA-capped CdS nanoparticles and their solubility in water

A single-source precursor route has been explored by using the diphenylthiourea cadmium complex as the source of cadmium sulphide (CdS) nanoparticles. The reaction was carried out using hexadecylamine (HDA) as the solvent and stabilising agent for the particles. The phenylthiourea complex was synthesised and characterised by means of a combination of spectroscopic techniques, microanalysis and X-ray crystal structural analysis. The diphenylthiourea complex was thermolysed in HDA at 120 °C for 1 h to produce CdS nanoparticles. The CdS nanoparticles prepared were made water-soluble via a ligand exchange reaction involving the use of pyridine to displace HDA. The pyridine was, in turn, replaced by glucose and glucuronic acid. The absorption and emission spectra showed the typical features of quantum confinement for the nanoparticles for both HDA-capped and glucose- or glucuronic acid-capped CdS nanoparticles. The change in the capping groups, from HDA to glucose and glucuronic acid, resulted in absorption and emission features that were almost similar, with only slight red-shifting and tailing.

Noncovalent Synthesis of Hierarchical Zinc Phosphates from a Single Zn4O12P4 Double‐Four‐Ring Building Block: Dimensionality Control through the Choice of Auxiliary Ligands

In contrast to the well-known reaction of phosphonic acids RP(O)(OH)(2) with divalent transition-metal ions that yields layered metal phosphonates [RPO(3)M(H(2)O)](n), the 2,6-diisopropylphenyl ester of phosphoric acid, dippH(2), reacts with zinc acetate in methanol under ambient conditions to afford tetrameric zinc phosphate [(ArO)PO(3)Zn(MeOH)](4) (1). The coordinated methanol in 1 can be readily exchanged by stronger Lewis basic ligands at room temperature. This strategy opens up a new avenue for building double-four-ring (D4R) cubane-based supramolecular assemblies through strong intercubane hydrogen-bonding interactions. Seventeen pyridinic ligands have been used to synthesize as many D4R cubanes [(ArO)PO(3)Zn(L)](4) (2-18) from 1. The ligands have been chosen in such a way that the majority of them contain an additional functional group that could be used for noncovalent synthesis of extended structures. When the ligand does not contain any other hydrogen-bonding donor-acceptor sites (e.g., 2,4,6-trimethylpyridine (collidine)), zero-dimensional D4R cubanes have been obtained. The use of pyridine, lutidine, 2-aminopyridine, and 2,6-diaminopyridine, however, results in the formation of linear or zigzag one-dimensional assemblies of D4R cubanes through strong intermolecular C-H...O or N-H...O interactions. Construction of two-dimensional assemblies of zinc phosphates has been achieved by employing 2-hydroxypyridine or 2-methylimidazole as the exo-cubane ligand on zinc centers. The introduction of an alcohol side chain on the pyridinic ligand in such a way that the -CH(2)OH group cannot participate in intracubane hydrogen bonding (e.g., pyridine-3-methanol, pyridine-4-methanol, and 3,5-dimethylpyrazole-N-ethanol) leads to the facile noncovalent synthesis of three-dimensional framework structures. Apart from being useful as building blocks for noncovalent synthesis of zeolite-like materials, compounds 1-18 can also be thermolyzed at approximately 500 degrees C to yield high-purity zinc pyrophosphate (Zn(2)P(2)O(7)) ceramic material.

In Vitro Characterization of AtsB, a Radical SAM Formylglycine-Generating Enzyme That Contains Three [4Fe-4S] Clusters

Sulfatases catalyze the cleavage of a variety of cellular sulfate esters via a novel mechanism that requires the action of a protein-derived formylglycine cofactor. Formation of the cofactor is catalyzed by an accessory protein and involves the two-electron oxidation of a specific cysteinyl or seryl residue on the relevant sulfatase. Although some sulfatases undergo maturation via mechanisms in which oxygen serves as an electron acceptor, AtsB, the maturase from Klebsiella pneumoniae, catalyzes the oxidation of Ser72 on AtsA, its cognate sulfatase, via an oxygen-independent mechanism. Moreover, it does not make use of pyridine or flavin nucleotide cofactors as direct electron acceptors. In fact, AtsB has been shown to be a member of the radical S-adenosylmethionine superfamily of proteins, suggesting that it catalyzes this oxidation via an intermediate 5'-deoxyadenosyl 5'-radical that is generated by a reductive cleavage of S-adenosyl- l-methionine. In contrast to AtsA, very little in vitro characterization of AtsB has been conducted. Herein we show that coexpression of the K. pneumoniae atsB gene with a plasmid that encodes genes that are known to be involved in iron-sulfur cluster biosynthesis yields soluble protein that can be characterized in vitro. The as-isolated protein contained 8.7 +/- 0.4 irons and 12.2 +/- 2.6 sulfides per polypeptide, which existed almost entirely in the [4Fe-4S] (2+) configuration, as determined by Mossbauer spectroscopy, suggesting that it contained at least two of these clusters per polypeptide. Reconstitution of the as-isolated protein with additional iron and sulfide indicated the presence of 12.3 +/- 0.2 irons and 9.9 +/- 0.4 sulfides per polypeptide. Subsequent characterization of the reconstituted protein by Mossbauer spectroscopy indicated the presence of only [4Fe-4S] clusters, suggesting that reconstituted AtsB contains three per polypeptide. Consistent with this stoichiometry, an as-isolated AtsB triple variant containing Cys --> Ala substitutions at each of the cysteines in its CX 3CX 2C radical SAM motif contained 7.3 +/- 0.1 irons and 7.2 +/- 0.2 sulfides per polypeptide while the reconstituted triple variant contained 7.7 +/- 0.1 irons and 8.4 +/- 0.4 sulfides per polypeptide, indicating that it was unable to incorporate an additional cluster. UV-visible and Mossbauer spectra of both samples indicated the presence of only [4Fe-4S] clusters. AtsB was capable of catalyzing multiple turnovers and exhibited a V max/[E T] of approximately 0.36 min (-1) for an 18-amino acid peptide substrate using dithionite to supply the requisite electron and a value of approximately 0.039 min (-1) for the same substrate using the physiologically relevant flavodoxin reducing system. Simultaneous quantification of formylglycine and 5'-deoxyadenosine as a function of time indicates an approximate 1:1 stoichiometry. Use of a peptide substrate in which the target serine is changed to cysteine also gives rise to turnover, supporting approximately 4-fold the activity of that observed with the natural substrate.

Pyridine-Free and Solvent-Free Acetylation of Nucleosides Promoted by Molecular Sieves

A practical method for the acetylation of purine and ­pyrimidine nucleosides employing a combination of acetic an­hydride and potassium-exchanged molecular sieves is described. Besides the high yields obtained for the acylated nucleosides, the procedure is simple, inexpensive and environmentally benign, avoiding the use of pyridine or co-solvents as additives.

Recolorization of museum specimens: a modification of Romhanyi’s technique based on pyridine/nicotine hemochromogen reactions

Romhanyi's technique for preservation and restoration of color in museum specimens is almost unknown outside Hungary. The technique was based on the use of pyridine, nicotine and sodium dithionite (sodium hydrosulphite) for restoring the natural red color of formalin-fixed gross specimens. We developed a modification of the original technique using a mounting medium containing citrate-phosphate-dextrose (CPD) buffer and glycerin to control pH and osmolality. Specimens re-colorized with the modified and improved Romhanyi technique remained stable with a natural red color, and no histological deterioration, for more than 18 years. The technique demonstrates the formation of red colored complexes between nicotine and pyridine and ferro-hemochromes such as hemoglobin, myoglobin and other cytochromes in tissues, giving specimens a natural color. The modified technique enables further improvement for the old process of re-colorization of museum specimens. In addition, it opens up new methods for demonstration of nicotine, pyridine and their analogues in biological tissues.

Decomposition of metal tetrasulphophthalocyanines incorporated in SiO2 gels

The aggregation of metal 2,9,16,23-tetrasulphophthalocyanines, MTSPc (M=Fe, Co, Ni, Cu and Al), embedded in transparent monolithic gels of silica, prepared by the sol–gel method has been successfully controlled by the addition of N,N-dimethylformamide (DMF) or pyridine (py). The utilization of DMF produces materials less prone to fracture and with better optical properties than those obtained by the use of pyridine. In the case of CuTSPc, CoTSPc and NiTSPc species with DMF (4% v/v) some colour fading in the gels was observed. The comparative study of gels prepared with M(II)TSPc (M=Cu, Ni and Co) and (OH)M(III)TSPc (M=Fe, Al) species has shown that loss of colour in solution and in the monoliths depends on the oxidation number of the cation. An interaction between the DMF and the metal macrocycle, favoring the disruption of the conjugated double bond system of the organic macrocycle has been originally proposed, but now evidence is given that the possible decomposition of the complex is caused by internal conditions prevailing in the gel. Experiments in alkaline solution confirm that, when trapped in gels, (OH)M(III)TSPc forms μ-oxo dimers, and M(II)TSPc decomposes.

Synthesis of acidic Al-MCM-48: influence of the Si/Al ratio, degree of the surfactant hydroxyl exchange, and post-treatment in NH 4F solution

Al-MCM-48 mesostructures with different Al contents (Si/Al = 40, 30, and 20) have been prepared with hydroxyl-exchanged cetyl-trimethylammonium bromide as the template and a post-synthesis treatment in NH 4F solution. The solid structures were analyzed by XRD, N 2 adsorption, DRIFT, SEM, HREM, and 27Al and 29Si MAS NMR. Moreover, surface acidity was determined with the use of pyridine (Py) and 2,6-dimethylpyridine (DMPy) as probe molecules. The catalytic activity of Al-MCM-48 materials in isopropylbenzene dealkylation was compared with those of the microporous H-Y and ZSM-5 zeolites and that of a commercial silica–alumina catalyst (Harshaw, Si235, 13 wt% alumina). For these solids, the catalytic activity was related to the tetrahedral or octahedral (probably AlO 5F species) aluminum for nonfluorinated and fluorinated catalysts, respectively.

Characterization of fullerene nanotubes prepared by the liquid–liquid interfacial precipitation method

C70 nanotubes were prepared by using pyridine and isopropyl alcohol and heated in air at 250 °C in order to eliminate the contained solvents ‘heat treated C70’. The C70 nanotubes were also successfully prepared by use of pyridine and isobutyl alcohol. The C70 nanotubes heated at 1100 °C in vacuum became amorphous carbon, but retained the tubular structure. The structural characteristics of these C70nanotubes are observed through their high-resolution transmission electron microscopy.

HClO 4–SiO 2 catalyzed per- O-acetylation of carbohydrates

An efficient per- O-acetylation of carbohydrates catalyzed by HClO 4–SiO 2 is reported using a stoichiometric quantity of acetic anhydride avoiding the use of pyridine and excess acetic anhydride under solvent-free conditions.

Self‐Limited Pore Size Reduction of Mesoporous Silica Membranes via Pyridine‐Catalyzed Silicon Dioxide ALD

The pore size of mesoporous silica membranes is reduced using pyridine‐catalyzed SiO2 ALD within the mesoporous matrix. The use of pyridine to catalyze the ALD results in lowering the reaction temperature to 80 °C. It also self‐limits the pore size reduction as shown in gas permeation experiments. The self‐limiting aspect of the deposition, controlled by size exclusion of catalyst from the pore, has the potential of controlling the pore size within the membrane. The paper concludes that this technique may prove useful as a general technique for healing defects in membranes.

Debenzylation of Tertiary Amines Using Phosgene or Triphosgene: An Efficient and Rapid Procedure for the Preparation of Carbamoyl Chlorides and Unsymmetrical Ureas. Application in Carbon‐11 Chemistry.

AbstractFor Abstract see ChemInform Abstract in Full Text.