[Show abstract][Hide abstract] ABSTRACT: Physico-chemical and biological properties of native polysaccharides could be greatly improved by changing their primary structure, conformation, water solubility or acidity. Chitosan is well-known for its biological properties. Nevertheless, its poor water solubility and its high molecular weight limit its potential uses as biological agent. Enzymatic hydrolysis or regioselective oxidation can be used to overcome these limitations and give birth to new active oligosaccharides.
Firstly, chitosan was C-6 oxidized with NaOCl/NaBr in the presence of TEMPO. 13C NMR, FT-IR and conductimetry analyses confirmed the C-6 oxidation. The production yield was closed to 11 % (w/w) and the molecular weight estimated to 2 kDa by SEC-MALLS experiments. The potential degradability of the derivative was investigated by glycoside hydrolases and polysaccharide lyases. Macerozyme R-10, Glucanex® and a crude extract from Trichoderma reesei IHEM 4122 showed the best degradation results. Finally, the antiparasite activity of the derivative was evaluated against Leishmania infantum LIPA 137. The toxicity of C-6 oxidized chitosan (IC50 = 125µg/mL) was one hundred times higher than current products used against promastigotes.
TEMPO chemistry highlighted the possibility to produce short size, soluble and non-sulfated hyaluronan-like mimetics. These derivatives will be of great interest to design new drugs in leishmaniosis treatment.
3rd EPNOE International Polysaccharide Conference, Nice, France; 10/2013
[Show abstract][Hide abstract] ABSTRACT: 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 reseei were used to degrade the C-6 oxidized chitosan. Glucanex®, the crude extract from Trichoderma 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(-1)) 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: 125μg/mL) of the obtained derivatives against Leishmania infantum LIPA 137.
International journal of biological macromolecules 06/2013; · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Polysaccharides are abundant biopolymers exhibiting various functional activities owing to their structural diversity. These macromolecules, easily renewable, are commonly used in food, oil, cosmetic or pharmaceutical industries. The use of native polysaccharides could be greatly improved by enhancing their properties. In this way, changes in the primary structure of polysaccharides through the addition of anionic/cationic charges, alkyl or sulfated groups modify their conformation, water solubility or acidity. The field of applications of these biopolymers is very wide but closely dependent on their solubility at neutral pH values, on their viscosity in aqueous solutions and on their molecular weight. Chitosan, which is a biopolymer composed of N¬-acetyl-D-glucosamine and D-glucosamine units linked by β-(1-4) bonds, is one example of bioactive polysaccharide insoluble in water at pH 7. Its poor water solubility limits its uses as biological agent. Besides, chitosan is an excellent candidate for chemical modifications, especially to produce glycosaminoglycan mimetics (GAGs), which are known for their dietary or cosmetic properties as the hyaluronic acid. The production of GAGs mimetics from a low cost biopolymer, such as chitosan, highlights major healthy and economic interests.
The first goal of this work was to produce oligoglycosaminoglycans (oligoGAGs) from chitosan by performing its oxidation through the use of 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO). Chitosan (90 % deacetylated and with a molecular weight of 150 kDa) was oxidized regiospecifically at C6 with NaOCl and NaBr for approximately 1 h at 4°C in the presence of TEMPO as a catalyst. 13C NMR analyses were carried out and confirmed the regioselective oxidation. Conductivity experiments showed an oxidation degree closed to 94 %. The production yield of these oligoGAGs mimetics was closed to 10.9 % ± 1.4 (w/w) by using this preparation process and their molecular weight closed to 2 KDa. The second aim was to evaluate the potential degradability of these oligoGAGs by glycoside hydrolases (GHs) and polysaccharide lyases (PLs). Cellulase, Celluclast 1.5 L, Glucanex, Macerozyme R-10, glucuronan lyase, rockfish chitinase and enzymatic mix from Trichoderma reseei were used to degrade the oligoGAGs mimetics. Effects of pH and temperature were also studied. Enzymatic degradations were followed by colorimetric assays and the use of Macerozyme R-10 and Glucanex showed the best degradation results.
Finally, TEMPO chemistry showed the possibility to easily produce soluble oligoGAGs mimetics. The short size of the oligoGAGs decreased the amount of enzymes required for the degradation but the biodegradability of these anionic chitosans was validated.
5th European Symposium POLYMERIX 2012, Rennes, France; 06/2012
[Show abstract][Hide abstract] ABSTRACT: The antioxidant properties of phenolic compounds from olive pulp (PCO) of chamlal variety and those of individual phenolic compounds were evaluated and compared with that of vitamin C (Vit C). The antioxidant activity was measured by the tests of iron reduction and scavenging hydrogen peroxide (H(2)O(2)). Results showed that all the substances tested exhibit a reducing power. The PCO present activities of iron reduction and H(2)O(2) scavenging higher than those of Vit C. The protective effect of PCO against oxidation of lipids and proteins from erythrocyte membranes was studied. The measurement of malondialdehyde generated under oxidative stress conditions induced by hydroxyl radicals generating system revealed that PCO have the most significant protective activity against lipid peroxidation (IC(50) = 49.27 ± 1.91 μg mL(-1)). Paradoxically, Vit C revealed a pro-oxidant effect. Proteins oxidation was evaluated using the H(2)O(2)/FeSO(4) system and electrophoresis. In the presence of PCO at 1 mg mL(-1), proteins of erythrocyte membranes were protected contrary to those treated with Vit C at the same concentration.
Applied biochemistry and biotechnology 03/2012; 167(6):1802-10. · 1.94 Impact Factor