Oxidation of curdlan and other polysaccharides by 4-acetamide-TEMPO/NaClO/NaClO2 under acid conditions
Oxidation of curdlan and other polysaccharides by 4-acetamide-TEMPO/NaClO/NaClO2 under acid conditions
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DOI：
10.1016/j.carbpol.2010.03.016
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发表时间：
2010-07
影响因子：
11.2
通讯作者：
N. Tamura;Masayuki Hirota;Tsuguyuki Saito;A. Isogai
中科院分区：
文献类型：
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作者：
N. Tamura;Masayuki Hirota;Tsuguyuki Saito;A. Isogai
在pH 4.7和35°C的水中，通过4-乙酰胺-TEMPO/NaClO/NaClO 2处理，将C6伯羟基区域选择性氧化为羧酸根，以制备解聚较少的水溶性氧化产物。通过在上述条件下氧化4- 24小时，可德兰的约40-95%的C6-OH基团转化为C6-羧酸酯基团，并且这些C6-氧化的可德兰变成水溶性的。虽然在氧化过程中部分解聚是不可避免的，但具有95%C6-羧化的氧化的可得然胶具有大于1000的重均聚合度。该值远高于在pH 10下通过常规克里思/NaBr/NaClO氧化制备的值。用4-乙酰胺-TEMPO/NaClO/NaClO_2在pH 4.7、35°C条件下氧化直链淀粉、淀粉和支链淀粉24 h，除直链淀粉外，其余氧化产物均溶于水。然而，氧化产物的羧酸根含量低于凝胶多糖。因此，（1→3）-β-葡聚糖的C6-OH基团比具有（1→4）-α-和（1→6）-α-糖苷键的葡聚糖更容易氧化。
Regioselective oxidation of C6 primary hydroxyls to carboxylate groups was applied to curdlan to prepare water-soluble oxidized products with less depolymerization by 4-acetamide-TEMPO/NaClO/NaClO2treatment in water at pH 4.7 and 35°C. Approximately 40–95% of the C6-OH groups of curdlan were converted to C6-carboxylate groups by the oxidation under the above conditions for 4–24h, and these C6-oxidized curdlans became water-soluble. Although partial depolymerization was inevitable during the oxidation, the oxidized curdlan with 95% C6-carboxylation had a weight-average degree of polymerization of more than 1000. This value was much higher than that prepared by the conventional TEMPO/NaBr/NaClO oxidation at pH 10. When the 4-acetamide-TEMPO/NaClO/NaClO2oxidation at pH 4.7 and 35°C for 24h was applied to amylose, starches and pullulan, all the oxidized products except amylose became water-soluble. Carboxylate contents of the oxidized products were, however, lower than that for curdlan. Thus, the C6-OH groups of (1→3)-β-glucan are more susceptible to the oxidation than those of glucans with (1→4)-α- and (1→6)-α-glycoside bonds.