RESUMO
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 â 4) linked ß-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.
Assuntos
Antioxidantes/química , Cactaceae/química , Galactanos/química , Extratos Vegetais/química , Antioxidantes/isolamento & purificação , Galactanos/isolamento & purificaçãoRESUMO
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.
Assuntos
Antioxidantes/síntese química , Óxidos N-Cíclicos/química , Polissacarídeos Bacterianos/química , Polissacarídeos/síntese química , Ácidos Urônicos/síntese química , Antioxidantes/química , Compostos de Bifenilo/química , Brometos/química , Catálise , Oxirredução , Picratos/química , Polissacarídeos/química , Compostos de Sódio/química , Hidróxido de Sódio/química , Hipoclorito de Sódio/química , Ácidos Urônicos/químicaRESUMO
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.
Assuntos
Radical Hidroxila/química , Oligossacarídeos/química , Pectinas/química , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Oligossacarídeos/isolamento & purificação , Plantas/químicaRESUMO
The filamentous fungus Trichoderma sp. GL2 produces an extracellular glucuronan lyase (GL) when grown on glucuronan as the sole carbon source. In this paper, we report the purification to electrophoretical homogeneity of this polysaccharide lyase by size exclusion chromatography and anion exchange chromatography. The purified GL, classified as an endopolyglucuronate lyase, is a monomer with an apparent molecular weight of 27 kDa and an isoelectric point of 6.95. Despite an inhibition of the activity when polysaccharide substrates were substituted by acetates, the enzyme was active toward glucuronans (acetylated or not) and ulvan, leading to various (4,5)-unsaturated products as oligoglucuronans (acetylated or deacetylated), highly acetylated low-molecular-weight (LMW) glucuronans, and LMW ulvans.
