Structure activity relationship of bergenin,p-hydroxybenzoyl bergenin, 11-O-galloylbergenin as potent antioxidant and urease inhibitor isolated from Bergenia ligulata

Ethanol extract of the aerial parts of Bergenia ligulata was subjected to solvent–solvent separation followed by various chromatographic techniques that lead to isolation of bergenine (1), p-hydroxybenzoyl bergenin (2), 11-O-galloylbergenin (3) and methyl gallate (4) as major constituents. Ethyl acetate fraction showed a dose-dependent urease inhibitory pattern with IC₅₀ value of 54μg/mL. Structures of compounds 1 and 3 were established by XRD and 2, 4 by NMR. All these compounds were subjected to DPPH scavenging activity, reducing power assay and urease inhibitory activity. The EC₅₀ 7.45 ± 0.2 μg/mL and 5.39 ± 0.28 μg/mL values in terms of antioxidant and reducing power, respectively, were less for 3. Compounds 1–3 showed moderate to significant urease inhibitory potential with IC₅₀ 57.1 ± 0.7, IC₅₀ 48.4 ± 0.3 and 38.6 ± 1.5. Antioxidant activities and urease inhibitory potential were investigated and compound 3 was found to be the most active.     

Separation of isorhamnetin 3‐sulphate and astragalin from Flaveria bidentis (L.) Kuntze using macroporous resin and followed by high‐speed countercurrent chromatography

D4020 resin offered the best dynamic adsorption and desorption capacity for total flavonoids based on the research results from ten kinds of macroporous resin. A column packed with D4020 resin was used to optimize the separation of total flavonoids from Flaveria bidentis (L.) Kuntze extracts. The content of flavonoids in the product was increased from 4.3 to 30.1% with a recovery yield of 90%. After the treatment with gradient elution on D4020 resin, the contents of isorhamnetin 3‐sulfate and astragalin were increased from 0.49 to 8.70% with a recovery yield of 74.1% and 1.16 to 30.8%, with a recovery yield of 92.2%, respectively. Further purification was carried out by one‐run high‐speed countercurrent chromatography yielding 4.5 mg of isorhamnetin 3‐sulfate at a high purity of 96.48% and yielding 24.4 mg of astragalin at a high purity of over 98.46%.     

Asymmetric Transfer Hydrogenation Catalyzed by Mesoporous MCM‐41‐Supported Chiral Ru‐Complex

Chiral N‐sulfonyldiamine was successfully anchored on mesoporous MCM‐41 silica. The MCM‐41‐supported chiral N‐sulfonyldiamine was used as an efficient heterogeneous chiral ligand in the asymmetric transfer hydrogenation of ketones. This heterogeneous system offered satisfactory enantioselectivities up to 94 % with excellent conversions.     

Effect of iron acetylacetonate on physico-chemical properties of waterglass based aerogels by ambient pressure drying

The effect of iron acetylacetonate on the physico-chemical properties of waterglass based silica aerogels by ambient pressure drying has been investigated. Doping the gels with iron acetylacetonat (FeAA) facilitates in the diminution of the density of the aerogels. The well established silica network provides effective confinement of FeAA nanoparticles which resists the collapse of silica network during ambient pressure drying. Therefore, in the present paper, the effects of FeAA on the physico-chemical properties of the aerogels have been studied by varying the FeAA:Na₂SiO₃ molar ratio from 3 × 10⁻⁴ to 6 × 10⁻⁴. The aerogels were prepared via ambient pressure drying and characterized by the bulk density, thermal conductivity and water contact angle. The aerogel’s surface morphology, elemental analysis and pore structure were characterized by means of EDAX and FTIR, TEM and N₂ adsorption- desorption analyzer. The high temperature hydrophobicity of these aerogels was checked by heating them in temperature controlled furnace. Silica aerogels with low density ~0.050 g/cc have been obtained using the molar ratio of Na₂SiO₃:H₂O:FeAA:Citric acid:TMCS at 1:146.67:3 × 10⁻⁴:0.54:9.46, respectively. EDAX and FTIR studies show that the iron species are entrapped in the mesoporous framework and not took part in the bonding with silica.     

Paenibacillus polymyxa PKB1 produces variants of polymyxin B-type antibiotics

Polymyxins are cationic lipopeptide antibiotics active against many species of Gram-negative bacteria. We sequenced the gene cluster for polymyxin biosynthesis from Paenibacillus polymyxa PKB1. The 40.8 kb gene cluster comprises three nonribosomal peptide synthetase-encoding genes and two ABC transporter-like genes. Disruption of a peptide synthetase gene abolished all antibiotic production, whereas deletion of one or both transporter genes only reduced antibiotic production. Computational analysis of the peptide synthetase modules suggested that the enzyme system produces variant forms of polymyxin B (1 and 2), with D-2,4-diaminobutyrate instead of L-2,4-diaminobutyrate in amino acid position 3. Two antibacterial metabolites were resolved by HPLC and identified by high-resolution mass spectrometry and MS/MS sequencing as the expected variants 3 and 4 of polymyxin B₁ (1) and B₂ (2). Stereochemical analysis confirmed the presence of both D-2,4-diaminobutyrate and L-2,4-diaminobutyrate residues.     

Chemical constituents of Jordanian propolis

Seventeen compounds, including a new lanostane triterpenoid, 24(Z)-1β-3β-dihydroxyeupha-7,24-dien-26-oic acid, have been isolated from the methanolic extracts of two samples of Jordanian propolis collected from two different places with different dominant flora. The structures of the isolated compounds were elucidated by spectral methods including IR, UV, MS and 1- and 2-D NMR.     

Axiomatisability problems for <Emphasis Type="Italic">S</Emphasis>-posets

Let \(\mathcal{C}\) be a class of ordered algebras of a given fixed type τ. Associated with the type is a first order language L _τ , which must also contain a binary predicate to be interpreted by the ordering in members of \(\mathcal{C}\). One can then ask the question, when is the class \(\mathcal{C}\) axiomatisable by sentences of L _τ ? In this paper we will be considering axiomatisability problems for classes of left S-posets over a pomonoid S (that is, a monoid S equipped with a partial order compatible with the binary operation). We aim to determine the pomonoids S such that certain categorically defined classes are axiomatisable. The classes we consider are the free S-posets, the projective S-posets and classes arising from flatness properties. Some of these cases have been studied in a recent article by Pervukhin and Stepanova. We present some general strategies to determine axiomatisability, from which their results for the classes of weakly po-flat and po-flat S-posets will follow. We also consider a number of classes not previously examined.     

On $$\gamma $$ γ - and local $$\gamma $$ γ -vectors of the interval subdivision

Journal of Algebraic Combinatorics - We show that the $$\gamma $$ -vector of the interval subdivision of a simplicial complex with a nonnegative and symmetric h-vector is nonnegative. In...     

Stellatic acid: a new class of sesterterpenoid; X-ray crystal structure

The complete structure of a unique tricyclic sesterterpene, stellatic acid, was established by X-ray diffraction of its p-bromophenacyl ester.