Aqueous Chemistry of Zirconium(IV) in Carbonate Media

The interactions between carbonate ions and zirconium oxychloride are studied by potentiometry, dialysis, and ¹³C‐ and ¹⁷O‐NMR spectroscopy in aqueous media. The nature of the soluble carbonatohydroxo complexes depends on the proportions of hydrogencarbonate and carbonate ions in solution before the addition of zirconium oxychloride. Carbonate media lead to polynuclear entities containing no more than two complexed carbonate ions per Zr⁴⁺. The presence of hydrogencarbonate favors the formation of less condensed and more carbonated complexes such as [Zr(CO₃)₄]⁴⁻. The polycondensation degree of the species decreases when the number of carbonates linked per Zr⁴⁺ increases. In all complexes, the carbonate is bidentate, and the metal atoms are linked via hydroxo bridges. The complexation of carbonate with Zr⁴⁺ occurs for a total carbonate concentration higher than 0.1M . Consequently, in natural medium, the speciation of this metal is governed only by the formation of hydroxo complexes.     

Neuropeltis acuminata (P. Beauv.): Investigation of the Chemical Variability and In Vitro Anti-inflammatory Activity of the Leaf Essential Oil from the Ivorian Species

The variability of chemical composition of the leaf essential oil (EO) from Neuropeltis acuminata, a climbing liana growing wild in Ivory Coast, was investigated for the first time. The in vitro anti-inflammatory activity was also evaluated. Thirty oil samples were isolated from leaves collected in three forests of the country and analyzed using a combination of Column Chromatography (CC), Gas Chromatography with Retention Indices (GC(FID)), Gas Chromatography-Mass Spectrometry (GC-MS), and ¹³Carbon-Nuclear Magnetic Resonance (¹³C-NMR). Fractionation by CC led to the first-time isolation from natural source of δ-cadinen-11-ol, whose structural elucidation by one dimension (1D) and 2D-NMR spectroscopy is reported here. Finally, 103 constituents accounting for 95.7 to 99.6% of the samples’ compositions were identified. As significant variations of the major constituents were observed, the 30 oil compositions were submitted to hierarchical cluster and principal components analyses. Five distinct groups were evidenced: Group I, dominated by (E)-β-caryophyllene, kessane, and δ-cadinene, while the main constituents of Group II were germacrene B, ledol, α-humulene, (E)-γ-bisabolen-12-ol, and γ-elemene. Group III exhibited guaiol, germacrene D, atractylone, (E)-γ-bisabolen-12-ol, δ-cadinene and bulnesol as main compounds. Group IV was dominated by (E)-nerolidol, guaiol, selina-4(15),7(11)-diene and bulnesol, whereas (E)-β-caryophyllene, α-humulene and α-muurolene were the prevalent compounds of Group V. As the harvest took place in the same dry season in the three forests, the observed chemical variability could be related to harvest sites, which includes climatic and pedologic factors, although genetic factors could not be excluded. The leaf oil sample S24 behaved as a high inhibitor of LipOXygenase (LOX) activity (half maximum Inhibitory Concentration, IC₅₀: 0.059 ± 0.001 mg mL⁻¹), suggesting an anti-inflammatory potential.     

Analysis of a Prototypical Multiscale Method Coupling Atomistic and Continuum Mechanics： the Convex Case

In order to describe a solid which deforms smoothly in some region,but non smoothly in someother region,many multiscale methods have been recently proposed that aim at coupling an atomistic model(discrete mechanics) with a macroscopic model (continuum mechanics).We provide here a theoretical basis forsuch a coupling in a one-dimensional setting,in the case of convex energy.     

Comparative Metabolomic Analysis of Four Fabaceae and Relationship to In Vitro Nematicidal Activity against Xiphinema index

The grapevine fanleaf virus (GFLV), responsible for fanleaf degeneration, is spread in vineyards by the soil nematode Xiphinema index. Nematicide molecules were used to limit the spread of the disease until they were banned due to negative environmental impacts. Therefore, there is a growing interest in alternative methods, including plant-derived products with antagonistic effects to X. index. In this work, we evaluated the nematicidal potential of the aerial parts and roots of four Fabaceae: sainfoin (Onobrychis viciifolia), birdsfoot trefoil (Lotus corniculatus), sweet clover (Melilotus albus), and red clover (Trifolium pratense), as well as that of sainfoin-based commercial pellets. For all tested plants, either aerial or root parts, or both of them, exhibited a nematicidal effect on X. index in vitro, pellets being as effective as freshly harvested plants. Comparative metabolomic analyses did not reveal molecules or molecule families specifically associated with antagonistic properties toward X. index, suggesting that the nematicidal effect is the result of a combination of different molecules rather than associated with a single compound. Finally, scanning electron microscope observations did not reveal the visible impact of O. viciifolia extract on X. index cuticle, suggesting that alteration of the cuticle may not be the primary cause of their nematicidal effect.     

Lead Isotopic Constraints on the Provenance of Antarctic Dust and Atmospheric Circulation Patterns Prior to the Mid-Brunhes Event (~430 kyr ago)

A lead (Pb) isotopic record, covering the two oldest glacial–interglacial cycles (~572 to 801 kyr ago) characterized by lukewarm interglacials in the European Project for Ice Coring in Antarctica Dome C ice core, provides evidence for dust provenance in central East Antarctic ice prior to the Mid-Brunhes Event (MBE), ~430 kyr ago. Combined with published post-MBE data, distinct isotopic compositions, coupled with isotope mixing model results, suggest Patagonia/Tierra del Fuego (TdF) as the most important sources of dust during both pre-MBE and post-MBE cold and intermediate glacial periods. During interglacials, central-western Argentina emerges as a major contributor, resulting from reduced dust supply from Patagonia/TdF after the MBE, contrasting to the persistent dominance of dust from Patagonia/TdF before the MBE. The data also show a small fraction of volcanic Pb transferred from extra-Antarctic volcanoes during post-MBE interglacials, as opposed to abundant transfer prior to the MBE. These differences are most likely attributed to the enhanced wet removal efficiency with the hydrological cycle intensified over the Southern Ocean, associated with a poleward shift of the southern westerly winds (SWW) during warmer post-MBE interglacials, and vice versa during cooler pre-MBE ones. Our results highlight sensitive responses of the SWW and the associated atmospheric conditions to stepwise Antarctic warming.     

H2O2: a Ca2+ or Mg2+‐sensing function in statin passive diffusion

In a previous paper Guillaume's group demonstrated that magnesium (Mg²⁺ concentration range 0.00–2.60 mm ) increased the passive diffusion of statins and thus played a role in their potential toxicity. In order to confirm an increase in this passive diffusion by divalent salt cations, the role of calcium chloride (CaCl₂) on the statin–immobilized artificial membrane (IAM) association was studied. It was demonstrated that calcium supplementation (Ca²⁺ concentration range 0.00–3.25 mm ) increases the statin passive diffusion. In addition, it was shown that the Ca²⁺ effect on the statin–IAM association is higher than that of Mg²⁺. These results show that Ca²⁺ enhances the passive diffusion of drugs into biological membranes and thus their potential toxicity. Also, addition of H₂O₂ to the medium showed a hyperbolic response for the statin passive diffusion and this effect was enhanced for the highest Ca²⁺ or Mg²⁺ concentrations in the medium. H₂O₂ is likely to interact with the polar head groups of the IAM through dipole–dipole interactions. The conformational changes in H₂O₂–IAM result in a higher degree of exposure of hydrophobic areas, thus explaining why the binding of pravastatin, which showed the lowest logP value, was less affected by H₂O₂. This result shows the significant contribution of H₂O₂ and thus the oxidative stress on the statin passive diffusion. Much of the sensitivity derives from the action of Ca²⁺ or Mg²⁺, in turn supported the idea that H₂O₂ may serve a Ca²⁺ or Mg²⁺ sensing function in statin passive diffusion Copyright © 2015 John Wiley & Sons, Ltd.