sodium-hypochlorite and curdlan

Pure (1→3)-β-polyglucuronic acid sodium salt was prepared from curdlan by oxidation with 4-acetamido-TEMPO/NaClO/NaClO₂ in water at pH 4.7 and 35°C. The oxidation conditions, including the reaction time and amounts of reagents added, were optimized for the preparation of (1→3)-β-polyglucuronic acids with high molecular weights. The primary C6 hydroxyl groups of curdlan were completely oxidized to the corresponding C6-carboxylates using a one- or two-step reaction process by controlling the oxidation conditions, thus providing pure (1→3)-β-polyglucuronic acids consisting only of D-glucuronosyl units. Unfortunately, however, the increased amounts of reagents and long reaction time led to significant depolymerization of the curdlan during the oxidation process, and the resulting (1→3)-β-polyglucuronic acids had weight-average degrees of polymerization of 340-360. The (13)C and (1)H NMR chemical shifts of the products were successfully assigned using pure (1→3)-β-polyglucuronic acid.

Topics: beta-Glucans; Carboxylic Acids; Catalysis; Chlorides; Cyclic N-Oxides; Glucuronic Acid; Oxidation-Reduction; Polymerization; Sodium Hypochlorite

Curdlan from Agrobacterium sp. was oxidized using 2,2,6,6,-tetramethylpiperidine-1-oxyl radical (TEMPO)-NaBr-NaClO systems at pH 11. The effects of oxidation conditions on degrees of oxidation and polymerization of the products obtained were studied using SEC-MALLS, NMR and IR analyses. Different families of water-soluble beta-(1,3)-polyglucuronic and beta-(1,3)-polyglucoglucuronic acid sodium salts were quantitatively generated with a yield of 80% and without significant loss of their molecular weights. Given that beta-(1,3)-polyglucuronic acids prepared from the regioselective oxidation of curdlan by the TEMPO-NaBr-NaClO systems regularly consist of the glucuronic acid repeating unit; they may open new biotechnological fields for the utilizations of water soluble forms of curdlan.

Topics: beta-Glucans; Carbohydrates; Cyclic N-Oxides; Electrochemistry; Glucuronates; Hydrogen-Ion Concentration; Magnetic Resonance Spectroscopy; Models, Chemical; Molecular Weight; Oxygen; Rhizobium; Sodium Hypochlorite; Spectrophotometry, Infrared; Spectroscopy, Fourier Transform Infrared; Water