Fractal structures and silica films formed by the Treignac water on inert and biological surfaces.

The Treignac water is a natural mineral water containing mainly orthosilicic acid. On inert substrates, it forms a silica film with fractal structures which cannot be reproduced in laboratory-reconstituted water. These structures form by condensation of orthosilicic acid monomers, following the Witten-Sander model of diffusion-limited aggregation.

Tolerance of Douglas Fir Somatic Plantlets to Aluminum Stress: Biological, Cytological, and Mineral Studies.

Aluminum (Al) is well known as a potent inhibitor of plant growth and development. It is notably present in soils in the soluble and bioavailable form Al when the soil pH drops below 5. This situation is frequent, especially in softwood forests when litter decomposition is slow.

Use of a Pleurotus ostreatus Complex Cell Wall Extract as Elicitor of Plant Defenses: From Greenhouse to Field Trial.

Fungi constitute an abundant source of natural polysaccharides, some of them harboring original structures which can induce responses in mammalian or plant cells. An alkaline extract from the edible mushroom Pleurotus ostreatus has been obtained and called Pleuran complex cell wall extract (CCWE). It consists of a glucan-peptide complex whose components fall in a quite broad range of molecular weights, from 30 to 80 kDa.

Antibacterial activity of the lichens and (Parmeliaceae).

Acetone extracts of the two common epiphytes lichens and have been evaluated for their antimicrobial activities against , and . The dibenzofuran derivative (+)-usnic acid () was the main metabolite in these two species. Thamnolic (), evernic (), physodic () and 3-hydroxyphysodic acids () were isolated from , as well as 5,7-dihydroxy-6-methylphtalide () which was newly identified in this .

Agar Extraction By-Products from as a Source of Glycerol-Galactosides.

Alkaline treatment is a common step largely used in the industrial extraction of agar, a phycocolloid obtained from red algae such as . The subsequent residue constitutes a poorly valorized by-product. The present study aimed to identify low-molecular-weight compounds in this alkaline waste.

Structural Investigation of Cell Wall Xylan Polysaccharides from the Leaves of Algerian Argania spinosa.

Xylan-type polysaccharides were isolated from the leaves of (L.) Skeels collected in the Tindouf area (southwestern Algeria). Xylan fractions were obtained by sequential alkaline extractions and purified on Sepharose CL-4B.

Physiological responses of the hybrid larch (Larix × eurolepis Henry) to cadmium exposure and distribution of cadmium in plantlets.

Phytoextraction of Cd is a growing biotechnology although we currently know few Cd hyperaccumulators, i.e., plant species able to accumulate at least 0.

Douglas fir (pseudotsuga menziesii) plantlets responses to as, PB, and sb-contaminated soils from former mines.

Phytoremediation of metalloids by conifers is not widely studied although they may be relevant for several contaminated sites, especially those located in cold areas and sometimes under dry climates. Here, seeds of Douglas fir were sown in greenhouse on three soils collected in two French former mines: a gold mine (soils L1 and L2) and a lead and silver mine (soil P). These soils are highly contaminated by Pb, As, and Sb at different concentrations.

Interfacial reactions between humic-like substances and lateritic clay: application to the preparation of "geomimetic" materials.

The aim of this study was to understand the mechanisms responsible for the strengthening of "geomimetic" materials, especially the chemical bonding between clay and humic substances. The mineral matter is lateritic clay which mainly consists in kaolinite, goethite, hematite and quartz. The other starting products are fulvic acid (FA) and lime.

Partial structural characterization and antioxidant activity of a phenolic-xylan from Castanea sativa hardwood.

4-O-Methylglucuronoxylans (MGX) were isolated from chestnut wood sawdust using two different procedures: chlorite delignification followed by the classical alkaline extraction step, and an unusual green chemistry process of delignification using phthalocyanine/H2O2 followed by a simple extraction with hot water. Antioxidant properties of both MGX were evaluated against the stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) by electronic spin resonance (ESR). IC50 of water-extracted MGX was found to be less than 225 μg mL(-1), in contrast with alkali-extracted MGX for which no radical scavenging was observed.

Uncommon chlorinated xanthone and other antibacterial compounds from the lichen Cladonia incrassata.

Bioassay-guided fractionation of an extract of the lichen Cladonia incrassata against Staphylococcus aureus led to a novel compound, 1,5-dihydroxy-2,4,6-trichloro-7-methylxanthone (1), along with six known compounds: (-)-usnic acid (2), didymic acid (3), condidymic acid (4), squamatic acid (5), thamnolic acid (6), and prasinic acid (7). Didymic, condidymic, and prasinic acids were isolated for the first time from C. incrassata.

Phytoremediation of cadmium-contaminated soils by young Douglas fir trees: effects of cadmium exposure on cell wall composition.

Douglas fir trees grown on an artificially Cd-contaminated soil, can tolerate this trace element (up to 68 mg/kg in soil) during several months. Most of the absorbed Cd is retained in roots (25 mg/kg DM), but transfer to aerial part is also effective. Showing the highest content, up to 6 mg/kg DM, among all the aboveground parts, barks seem to be a preferred storage compartment.

Optimization of the arsenazo-III method for the determination of uranium in water and plant samples.

This work reports a reliable, fast and optimized photometric technique based on the specific chemical complexation of uranyl ion with arsenazo-III. In the case of solid samples (plant samples), for which mineralization under acidic and oxidative conditions was used, addition of ascorbic acid led to stabilization of the arsenazo-uranyl complex over time. The results, in total agreement with data obtained from α and γ spectrometries, demonstrate that the present technique is able to precisely quantify uranium in water as well as in plant samples, within the μg/L and mg/g ranges respectively.

Hybrid larch (Larix x eurolepis Henry): a good candidate for cadmium phytoremediation?

Studies related to phytoremediation by conifers are still at their beginning. Thus, we investigated the ability of a hybrid larch (Larix x eurolepis) to accumulate cadmium (Cd). One-month-old clonal plantlets grown in vitro were exposed for 1 week to a high Cd concentration (1.

Structural characterization and cytotoxic properties of an apiose-rich pectic polysaccharide obtained from the cell wall of the marine phanerogam Zostera marina.

Zosterin, an apiose-rich pectic polysaccharide, was extracted and purified from the sea grass Zostera marina. Structural studies conducted by gas chromatography and NMR spectroscopy on a purified zosterin fraction (AGU) revealed a typical apiogalacturonan structure comprising an alpha-1,4-d-galactopyranosyluronan backbone substituted by 1,2-linked apiofuranose oligosaccharides and single apiose residues. The average molecular mass of AGU was estimated to be about 4100 Da with a low polydispersity.

Aqueous extraction of glucuronoxylans from chestnut wood: new strategy for lignin oxidation using phthalocyanine or porphyrin/H2O2 system.

Hardwood 4-O-methylglucuronoxylans (MGX) are classically isolated by a delignification step, using a sodium chlorite solution, followed by alkaline extraction, an efficient, although potentially polluting process. In this work, we propose a chlorine-free environmentally-friendly process for MGX extraction from Castanea sativa Mill. Chestnut sawdust was first delignified using metalled phthalocyanine or porphyrin in presence of hydrogen peroxide.

Structural characterization and cytotoxic properties of a 4-O-methylglucuronoxylan from castanea sativa. 2. Evidence of a structure-activity relationship.

Xylans were purified from delignified holocellulose alkaline extracts of Castanea sativa (Spanish chestnut) and Argania spinosa (Argan tree) and their structures analyzed by means of GC of their per-trimethylsilylated methylglycoside derivatives and (1)H NMR spectroscopy. The structures deduced were characteristic of a 4-O-methylglucuronoxylan (MGX) and a homoxylan (HX), respectively, with degrees of polymerization ranging from 182 to 360. In the case of MGX, the regular or random distribution of 4-O-methylglucuronic acid along the xylosyl backbone--determined by MALDI mass spectrometry after autohydrolysis of the polysaccharide--varied and depended both on the botanical source from which they were extracted and on the xylan extraction procedure.

Structural patterns of rhamnogalacturonans modulating Hsp-27 expression in cultured human keratinocytes.

Polysaccharide extracts were obtained from chestnut bran (Castanea sativa), grape marc (Vitis vinifera) and apple marc (Malus spp.) and fractionated by size exclusion chromatography after endopolygalacturonase degradation. Compositional and linkage analyses by GC and GC-MS showed the characteristic rhamnogalacturonan structure with specific arabinan (apple marc) and type II arabinogalactan (chestnut bran, grape marc) side chains.

Bioactive capsular polysaccharide from the thermophilic cyanophyte/cyanobacterium Mastigocladus laminosus - cytotoxic properties.

The capsular polysaccharide produced by the thermophilic blue green alga/cyanobacterium Mastigocladus laminosus was tested for its cytotoxic activity against the A431 human epidermoid carcinoma cell line. This polysaccharide inhibited the proliferation of A431 cells in a dose-dependent manner with an IC (50) value of 50 microg mL (-1). In addition, this polysaccharide strongly inhibited A431 cell migration and invasion.

Structural characterization and cytotoxic properties of a 4-O-methylglucuronoxylan from Castanea sativa.

A glucuronoxylan was purified from a delignified holocellulose alkaline extract of Castanea sativa (Spanish chestnut) and its structure analyzed by means of FT-IR, GC of the per-trimethylsilylated methylglycoside derivatives, and 1H and 13C NMR spectroscopy. The results supported a structure based on a linear polymer of xylopyranose units linked with beta(1-->4) bonds in which, on average, one out of every six units is substituted at C-2 by a 4-O-methylglucuronic acid unit; this structure is typical of a hardwood acidic 4-O-methylglucuronoxylan (MGX) with an estimated degree of polymerization of 200. The MGX from C.

Capsular polysaccharides secreted by building façade colonisers: characterisation and adsorption to surfaces.

Exopolymers secreted by algal and cyanobacterial strains isolated from building façades were imaged by microscopy techniques. They were extracted and characterised to investigate their possible contribution to interactions with solid surfaces. The polymers were polysaccharides, with anionic and hydrophobic properties varying between the various strains.

Study of the chemical interaction between barks and heavy metal cations in the sorption process.

The chemical mechanism displayed in the sorption of heavy metal cations on barks was discussed through a modelling study of adsorption in relation to the nature of the ligand borne by the chemical components of the bark sorbent. The adsorption isotherms of five heavy metal cations (Cr3 +, Cu2 +, Ni2 +, Pb2 +, Zn2+) on five species of barks (Sweet chestnut, Oak, Douglas fir, Norway spruce, Scots pine species) were studied. The experimental data fitted well the Langmuir model, which allowed the expression of the mathematical parameters (qmax, maximum binding capacity; b, affinity).

Conformational analysis of xylan chains.

The present study provides a theoretical description of the different levels of structural organization that characterize the xylan polysaccharide in its native and hydrophobic lauroyl esterified forms. The goal of this study was to ascertain the role played by the hydroxyl or lauroyl side groups on the conformational flexibility of the xylan chain backbone. The results reported provide a detailed description of the low-energy conformers of the dimer segments, a complete characterization of the helical structures, an insight into the disordered state of the polysaccharide chains and an estimation of the cohesion of the amorphous solids.

Chemical valorization of forest and agricultural by-products. Obtention, chemical characteristics, and mechanical behavior of a novel family of hydrophobic films.

Esterification of hemicelluloses of the xylan family was performed in order to produce hydrophobic films. Acylation reactions were carried out with lauroyl chloride in the N,N-dimethylacetamide/lithium chloride homogeneous system using 4-dimethylaminopyridine as activator and were induced by microwave irradiation. In the experimental conditions used, 108 and 172% mass ratios were obtained for the dodecyl-grafted xylan and heteroxylan, respectively.

The extracellular polysaccharide of Porphyridium sp.: an NMR study of lithium-resistant oligosaccharidic fragments.

This study deals with the chemical characterization of an extracellular polysaccharide produced by the unicellular red alga Porphyridium sp. The sugar moiety of this polymer is composed of three neutral monosaccharides (Xyl, Glc, and Gal) and one uronic acid (GlcA). Proteins represent 5.