Thermodynamics of formation for the 18-crown-6-triglycine molecular complex in water-dimethylsulfoxide solvents

The effect of a water-dimethylsulfoxide (DMSO) solvent on the formation of a molecular complex of 18-crown-6 (18C6) with triglycine (diglycylglycine, 3Gly) is studied via calorimetric titration. It is found that switching from water to an H₂O-DMSO mixture with DMSO mole fraction of 0.30 is accompanied by a monotonic increase in the stability of [3Gly18C6] complex, from logK ^° = 1.10 to logK ^° = 2.44, and an increase in the exothermicity of the reaction of its formation, from ?5.9 to ?16.9 kJ/mol. It is shown that the [3Gly18C6] complex exhibits enthalpy stabilization with negative values of enthalpy and entropy over the investigated range of H₂O-DMSO solvents. Analysis of the reagents’ solvation characteristics reveals that the increase in the reaction’s exothermicity of transfer is due to differences in the solvation of [3Gly18C6] and 18C6 with a small solvation contribution from 3Gly. It is concluded that the change in the Gibbs energy of the reaction 3Gly_solv + 18C6_solv ? [3Gly18C6]_solv is due to differences in the change in the solvation state of the complex and the peptide (Δ_tr G ^°([3Gly18C6])-Δ_tr G ^°(3Gly)).     

Iriomoteolide-13a,a cytotoxic 22-membered macrolide from a marine dinoflagellate Amphidinium species

Iriomoteolide-13a (1) has been isolated from a benthic dinoflagellate Amphidinium sp. (strain KCA09053) as a new 22-membered macrolide containing one hexahydrofuro[3,2-b]furan ring, one tetrahydropyran ring, two tetrahydrofuran rings, three one-carbon branches, and three hydroxyl groups including two hemiketals. The structure of 1 was assigned on the basis of a detailed 2D NMR analysis. Compound 1 exhibited cytotoxic activity against human cervix adenocarcinoma HeLa cells (IC₅₀: 0.5 μg/mL).     

Phospho sulfonic acid as an efficient and recyclable solid acid catalyst for the solvent-free preparation of acylals

Phospho sulfonic acid (PSA) acts as a highly effective and reusable catalyst for the chemo-selective protection of aldehydes with acetic anhydride under solvent-free conditions. The desirable features of this new catalytic methodology include its sustainability, effectiveness in the absence of solvent, a facile work-up procedure, and economic viability. PSA is fully characterized by Fourier transform infrared spectroscopy, wide-angle X-ray scattering analysis, and scanning electron microscopy with energy dispersive X-ray spectroscopy. The catalyst can be reused several times without significant loss of activity. In addition, no chromatographic separations are needed to obtain the desired products.     

Application of UPLC-QTOF-MS in MSE mode for the rapid and precise identification of alkaloids in goldenseal (Hydrastis canadensis)

Here, we describe a new application of ultra-performance liquid chromatography coupled with an electrospray ionization quadrupole time-of-flight mass spectrometry operating in MS^E mode (UPLC-QTOF-MS^E) for the sensitive, fast, and effective characterization of alkaloids in goldenseal (Hydrastis canadensis). This approach allowed identification of alkaloids using a cyclic low and high collision energy spectral acquisition mode providing simultaneous accurate precursor and fragment ion mass information. A total of 45 compounds were separated and 40 of them characterized including one new compound and 7 identified for the first time in goldenseal. The spectral data obtained using this method is comparable to those obtained by conventional LC-MSⁿ. However, the UPLC-QTOF-MS^E method offers high chromatographic resolution with structural characterization facilitated by accurate mass measurement in both MS and MS/MS modes in a single analytical run; this makes it suitable for the rapid analysis and screening of alkaloids in plant extracts.

Study of the isomeric ratios in 107Ag(γ, n)106m,gAg reaction of natural silver induced by bremsstrahlungs with endpoint energies in the giant dipole resonance region

We measured for the first time the isomeric ratios in ¹⁰⁷Ag(γ, n)^106m,gAg reaction by using the activation method and γ-ray spectroscopic method for the whole giant dipole resonance region. The high-purity natural Ag foils in disc shape were irradiated with bremsstrahlungs generated from an electron accelerator Microtron. The induced gamma spectra in the irradiated foils were measured by the high resolution γ-ray spectroscopic system which consists of a high-purity germanium detector and a multichannel analyzer. In order to improve the accuracy of the experimental results, necessary corrections were made in the γ-ray activity measurements and data analysis. The results were analyzed, discussed and compared with those of other authors. For the above mentioned reaction, the isomeric ratios in the energy range from 14 to 24 MeV bremsstrahlungs in this work (except the values at 14, 18 and 20) are new measurements.     

Spontaneous organization of uniform CeO2 nanoflowers by 3D oriented attachment in hot surfactant solutions monitored with an in situ electrical conductance technique

Uniform CeO(2) nanoflowers were synthesized by rapid thermolysis of (NH(4))(2)Ce(NO(3))(6) in oleic acid (OA)/oleylamine (OM), by a unique 3D oriented-attachment mechanism. CeO(2) nanoflowers with controlled shape (cubic, four-petaled, and starlike) and tunable size (10-40 nm) were obtained by adjusting the reaction conditions including solvent composition, precursor concentration, reaction temperature, and reaction time. The nanoflower growth mechanism was investigated by in situ electrical conductance measurements, transmission electron microscopy, and UV/Vis spectroscopy. The CeO(2) nanoflowers are likely formed in two major steps, that is, initial formation of ceria cluster particles capped with various ligands (e.g., OA, OM, and NO(3) (-)) via hydrolysis of (NH(4))(2)Ce(NO(3))(6) at temperatures in the range 140-220 degrees C, and subsequent spontaneous organization of the primary particles into nanoflowers by 3D oriented attachment, due to a rapid decrease in surface ligand coverage caused by sudden decomposition of the precursor at temperatures above 220 degrees C in a strong redox reaction. After calcination at 400 degrees C for 4 h the 33.8 nm CeO(2) nanoflowers have a specific surface area as large as 156 m(2) g(-1) with high porosity, and they are highly active for conversion of CO to CO(2) in the low temperature range of 200-400 degrees C. The present approach has also been extended to the preparation of other transition metal oxide (CoO, NiO, and CuO(x)) nanoflowers.     

Polysciosides J and K,two new oleanane-type triterpenoid saponins from the leaves of Polyscias fruticosa (L.) harms. cultivating in An Giang Province,Viet Nam

Abstract

For the first time, the phytochemical constituents of the leaves of Polyscias fruticosa (L.) Harms. cultivating in An Giang Province, Viet Nam were investigated and led to purify two new oleanane-type triterpenoid saponins, named polyscioside J (1) and polyscioside K (2) together with two known saponins, ladyginoside A (3) and chikusetsusaponin IVa (4) using variously chromatographic methods. Saponin (4) was reported for the first time from this species. Their structures were verified by IR, UV, HR-ESI-MS, NMR 1D and 2D experiments and compared with previous literatures.     

原位相分离合成V_2O_5/Fe_2V_4O_(13)纳米复合材料及其储钠性能

钠具有资源丰富、成本低廉等优势,因此钠离子电池被认为是未来替代锂离子电池的最佳候选者之一。然而,寻找合适的电极材料是当前制备高性能钠离子电池面临的难题之一。在众多候选材料中,钒酸盐材料通过引入阳离子增加钒的配位数,使得材料结构的稳定性得到提高,从而改善了钠离子电池的电化学性能。本文研究了一种原位相分离法合成V_2O_5/Fe_2V_4O_(13)纳米复合材料。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)等对电极材料形貌、组成和结构进行了表征。实验结果显示,V_2O_5/Fe_2V_4O_(13)纳米复合材料相对于V2O5纳米线材料,结构更加稳定,在0.1 A·g~(-1)电流密度下,初始放电容量由295.4 m Ah·g~(-1)提升到342 m Ah·g~(-1),循环100圈容量保持率由26.6%提高到65.8%,获得了更加优异的倍率性能(在1.0 A·g~(-1)电流密度下,容量由44 m Ah·g~(-1)提高到160 m Ah·g~(-1))。因此,V_2O_5/Fe_2V_4O_(13)纳米复合材料的研究为开拓新型高性能钠离子电池负极材料拓宽了思路。     

Auroglaucin-related neuroprotective compounds from Vietnamese marine sediment-derived fungus Aspergillus niveoglaucus

Abstract

Two new auroglaucin-derived compounds, niveoglaucins A (1) and B (2), together with four known related compounds were isolated from extract of the marine sediment-derived strain of Aspergillus niveoglaucus. The structures of these compounds were determined by 1D and 2D NMR spectroscopy and high resolution MS. The plausible biosynthetic pathway was proposed for new compounds 1 and 2. The neuroprotective activity in 6-OHDA-induced Parkinson’s disease cell model was shown for niveoglaucin A (1).     

Prenylated flavonoids with PTP1B inhibitory activity from the root bark of Erythrina mildbraedii

Phytochemical study on an EtOAc-soluble extract of the root bark of Erythrina mildbraedii resulted in the isolation of six prenylated flavonoids 1-6. Based on physicochemical and spectroscopic analyses, their structures were determined to be new natural products licoflavanone-4'-O-methyl ether (1), 2',7-dihydroxy-4'-methoxy-5'-(3-methylbut-2-enyl)isoflavone (2), and (3R)-2',7-dihydroxy-3'-(3-methylbut-2-enyl)-2',2'-dimethylpyrano[5',6' :4',5']isoflavan (3), along with three known compounds erythrinin B (4), abyssinin II (5), and parvisoflavone B (6). All the isolates, except for compound 4, inhibited PTP1B activity in vitro with IC(50) values ranging from 5.3 to 42.6 microM. This result further suggests that the prenyl group on the B ring of flavonoids plays an important role in suppressing the enzyme PTP1B.