Mounir Traïkia

Improved Copper(I)–NHC Catalytic Efficiency on Huisgen Reaction by Addition of Aromatic Nitrogen Donors

A simple addition with a large impact: Addition of aromatic amines such as phenanthroline and 4-DMAP (4-dimethylaminopyridine) increases copper(I)-catalyzed azide alkyne cycloaddition (CuAAC) catalytic activity of [CuCl(SIMes)] at a large range of temperatures in such a way that efficient catalysis can safely take place in hydro-alcoholic solvents (see scheme).

Antioxidant activities of a polyglucuronic acid sodium salt obtained from TEMPO-mediated oxidation of xanthan

A xanthouronic acid sodium salt called xanthouronan was produced from xanthan by regioselective oxidation with NaOCl/NaBr using 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) as catalyst. The efficiency of the one pot TEMPO-mediated oxidation was confirmed by HPAEC-PAD, (13)C NMR, and FT-IR. The oxidation degree was close to 98% and the mass yield of this new polyglucuronic acid was higher than 90% (w/w). The macromolecular characterization of xanthouronan using SEC-MALLS showed a molecular size reduced by a third due to the oxidation treatment and the degree of polymerization (DP) of the xanthouronan form was about 665. The evaluation of the enzymatic degradation of this C-6 carboxylated xanthan by various polysaccharide hydrolases and one polysaccharide lyase showed its high resistant to biodegradation. The antioxidant activity of xanthouronan was also tested by using the 2,2-diphenyl-1-picrylhydrazyle (DPPH) and hydroxyl radical procedures. At 1 g/L, xanthouronan presented 75% of the ascorbic acid antioxidant activity.

Enzymatic degradation and bioactivity evaluation of C-6 oxidized chitosan

C-6 oxidized chitosan was produced from chitosan by performing selective oxidation with NaOCl and NaBr using 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) as catalyst. Endocellulase, Celluclast 1.5 L, Glucanex(®), Macerozyme R-10, hyaluronidase, hyaluronate lyase, red scorpionfish chitinase, glucuronan lyase and a protein mix from Trichoderma reesei were used to degrade the C-6 oxidized chitosan. Glucanex(®), the crude extract from T. reesei IHEM 4122 and Macerozyme R-10 validated the enzymatic degradation through final hydrolysis yields of the derivative respectively close to 36.4, 20.3 and 12.9% (w/w). The best initial reaction velocity (2.41 U/mL) was observed for Glucanex(®). The antileishmanial activity of the derivative was evaluated against Leishmania infantum LIPA 137. The antibacterial activities against Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 were also tested. Results showed an antileishmanial activity (IC50: 125 μg/mL) of the obtained derivatives against L. infantum LIPA 137.

2-Aminobenzothiazole degradation by free and Ca-alginate immobilized cells of Rhodococcus rhodochrous

2-Aminobenzothiazole (ABT) degradation was investigated using free and immobilized systems during photodegradation under solar light in the presence of Fe(III)-nitrilotriacetic acid (FeNTA), biodegradation by Rhodococcus rhodochrous, and during combined conditions. Ca-alginate hydrogel was chosen as a model matrix and some complementary studies were required to characterize this new system. R. rhodochrous metabolism in this type of environment was monitored by NMR spectroscopy. Neither change in intracellular pH values nor in ATP concentrations was observed by in vivo(31)P NMR, showing that no metabolic modification occurred between free and immobilized cells. (1)H NMR demonstrated that alginate was not used as carbon source by R. rhodochrous. After establishing the pre-treatment protocol by SPE to eliminate solubilised alginate, ABT adsorption on beads and degradation were studied. The same pathways of transformation were observed in suspended and immobilized cell systems. Considering the ABT adsorption phenomenon on alginate beads (8%), the efficiency of the two systems was found to be comparable although the degradation rate was slightly lower with immobilized cells. The most important result was the finding that the positive effect of FeNTA on ABT degradation with immobilized cells was similar to that observed previously with free cells. All these results show that mechanisms observed with free cells can be extrapolated to entrapped cells, i.e. under conditions much closer to those usually encountered in the environment.

Effect of Nitrile-Functionalization of Imidazolium-Based Ionic Liquids on Their Transport Properties, Both Pure and Mixed with Lithium Salts

The influence of the presence of a nitrile group in the cation of imidazolium-based ionic liquids on their transport properties was investigated. As these liquids can be used as electrolytes in lithium ion batteries, their mixtures with lithium salts were also considered. 1-Butyl-3-methylimidazolium bis(trifluoromethylsulphonyl)imide, [C1C4Im][NTf2], 1-butylnitril-3-methylimidazolium bis(trifluoromethylsulphonyl)imide, [C1C3CNIm][NTf2], and their mixtures with bis(trifluoromethylsulphonyl)imide lithium, Li[NTf2], were studied. Their mass transport properties (viscosity, ionic conductivity, self-diffusion) were experimentally determined. NMR spectroscopy was also used to explore molecular organization and interactions in these systems. The addition of a cyano group increases the viscosity and the ionicity of the liquid. The effect of lithium ion is more pronounced on [C1C3CNIm][NTf2], with interactions between Li+ and the nitrile group.