Redouan Elboutachfaiti

Characterization of arabinogalactan-rich mucilage from Cereus triangularis cladodes

Cereus triangularis (Cactaceae) is a cactus used in food decoction as a traditional medicine in the North region of Madagascar to reduce stomach ache and intestinal diseases. Hydrocolloids were sequentially extracted from its cladodes with a yield of 24% (240 mg/g based on dried cladodes powder). Structural analyses has revealed that this polysaccharide with a molecular mass of 8430,000g/mol was mainly composed of a galactan backbone of a (1 → 4) linked β-d-Galp residues probably substituted at position 3 by L-arabinofuranosyl residues. In vitro antioxidant activity of this arabinogalactan-rich fraction was detected and quantified by radical DPPH scavenging, hydroxyl radical scavenging, radical anion superoxide scavenging and reducing power method.

Anti-biofilm activity: a function of Klebsiella pneumoniae capsular polysaccharide.

Competition and cooperation phenomena occur within highly interactive biofilm communities and several non-biocides molecules produced by microorganisms have been described as impairing biofilm formation. In this study, we investigated the anti-biofilm capacities of an ubiquitous and biofilm producing bacterium, Klebsiella pneumoniae. Cell-free supernatant from K. pneumoniae planktonic cultures showed anti-biofilm effects on most Gram positive bacteria tested but also encompassed some Gram negative bacilli. The anti-biofilm non-bactericidal activity was further investigated on Staphylococcus epidermidis, by determining the biofilm biomass, microscopic observations and agglutination measurement through a magnetic bead-mediated agglutination test. Cell-free extracts from K. pneumoniae biofilm (supernatant and acellular matrix) also showed an influence, although to a lesser extend. Chemical analyses indicated that the active molecule was a high molecular weight polysaccharide composed of five monosaccharides: galactose, glucose, rhamnose, glucuronic acid and glucosamine and the main following sugar linkage residues [→2)-α-l-Rhap-(1→]; [→4)-α-l-Rhap-(1→]; [α-d-Galp-(1→]; [→2,3)-α-d-Galp-(1→]; [→3)-β-d-Galp-(1→] and, [→4)-β-d-GlcAp-(1→]. Characterization of this molecule indicated that this component was more likely capsular polysaccharide (CPS) and precoating of abiotic surfaces with CPS extracts from different serotypes impaired the bacteria-surface interactions. Thus the CPS of Klebsiella would exhibit a pleiotropic activity during biofilm formation, both stimulating the initial adhesion and maturation steps as previously described, but also repelling potential competitors.

Osmotic stress alters the balance between organic and inorganic solutes in flax (Linum usitatissimum).

Flax (Linum usitatissimum) is grown for its oil and its fiber. This crop, cultivated in temperate regions, has seen a renewed interest due to the presence of abundant molecules of interest for many applications. Little information is available about the behavior of flax during osmotic stress; yet this is considered a major stress that causes significant yield losses in most crops. To control the presence of this stress better, flax behavior was investigated following the application of osmotic stress and the response was examined by applying increasing concentrations of PEG 8000. This resulted in the reorganization of 32 metabolites and 6 mineral ions in the leaves. The analysis of these two types of solute highlighted the contrasting behavior between a higher metabolite content (particularly fructose, glucose and proline) and a decrease in mineral ions (especially nitrate and potassium) following PEG treatment. However, this reorganization did not lead to a greater accumulation of solutes, with the total amount remaining unchanged in leaves during osmotic stress.

Oligogalacturonans production by free radical depolymerization of polygalacturonan

The large production of acidic oligosaccharides was investigated by non-enzymatic depolymerization of polygalacturonic acid (PGA) using free hydroxyl radical hydrolysis process from H2O2/copper (II) system. A large amount of oligogalacturonides (OGAs) with degrees of polymerization up to 6 were fractionated, and characterized by ESI-Q/TOF-MASS spectrometry and 1H NMR spectroscopy. This efficient production of uronic oligosaccharides from PGA constitutes an original process to produce bioactive compounds in large scale up.

β-Aminobutyric acid increases drought tolerance and reorganizes solute content and water homeostasis in flax (Linum usitatissimum)

Abstractβ-Aminobutyric acid (BABA) is a non-protein amino acid that induces drought tolerance in plants. The mechanisms involved in this tolerance are still poorly understood. In the present study, metabolomic and ionomic profiling performed in flax (Linum usitatissimum) leaves revealed that BABA induces a major reorganization in solute content. This reorganization resulted in increased accumulation of non-structural carbohydrates and proline and a decrease in inorganic solutes. This response has high similarities with that obtained when flax is exposed to an osmotic stress. BABA treatment also induced a decrease in osmotic potential and a change in water status of flax leaves. These modifications are accompanied by an improvement in drought tolerance.

Oligogalacturonic Acid Inhibits Vascular Calcification by Two Mechanisms: Inhibition of Vascular Smooth Muscle Cell Osteogenic Conversion and Interaction With Collagen

Objective— Cardiovascular diseases constitute the leading cause of mortality worldwide. Calcification of the vessel wall is associated with cardiovascular morbidity and mortality in patients having many diseases, including diabetes mellitus, atherosclerosis, and chronic kidney disease. Vascular calcification is actively regulated by inductive and inhibitory mechanisms (including vascular smooth muscle cell adaptation) and results from an active osteogenic process. During the calcification process, extracellular vesicles (also known as matrix vesicles) released by vascular smooth muscle cells interact with type I collagen and then act as nucleating foci for calcium crystallization. Our primary objective was to identify new, natural molecules that inhibit the vascular calcification process. Approach and Results— We have found that oligogalacturonic acids (obtained by the acid hydrolysis of polygalacturonic acid) reduce in vitro inorganic phosphate–induced calcification of vascular smooth muscle cells by 80% and inorganic phosphate–induced calcification of isolated rat aortic rings by 50%. A specific oligogalacturonic acid with a degree of polymerization of 8 (DP8) was found to inhibit the expression of osteogenic markers and, thus, prevent the conversion of vascular smooth muscle cells into osteoblast-like cells. We also evidenced in biochemical and immunofluorescence assays a direct interaction between matrix vesicles and type I collagen via the GFOGER sequence (where single letter amino acid nomenclature is used, O=hydroxyproline) thought to be involved in interactions with several pairs of integrins. Conclusions— DP8 inhibits vascular calcification development mainly by inhibition of osteogenic marker expression but also partly by masking the GFOGER sequence—thereby, preventing matrix vesicles from binding to type I collagen.