硫酸化修饰对椰子吸器多糖结构和抗氧化活性的影响

Effects of Sulfated Modification on the Structural Characterization and Antioxidant Activities of Coconut(Cocos nucifera L.)Haustorium Polysaccharide

为探讨硫酸化修饰对椰子吸器多糖(Coconut Haustorium Polysaccharide,CHP)结构功能的影响,以椰子吸器为原料,提取多糖后分别用含有不同比例的氯磺酸-吡啶(v/v,mL/mL:1/2、1/3和1/4)的硫酸化试剂制备3种硫酸化椰子吸器多糖(SCHP-2、SCHP-3、SCHP-4),并对其基本化学组成、结构特征和体外抗氧化活性进行对比分析。结果表明,三种硫酸化试剂都能对CHP进行分子修饰(红外光谱中1100~1250 cm^(-1)和820 cm^(-1)附近分别有S=O和C-O-S的特征峰),且氯磺酸/吡啶为1:2时的取代度(Degree of Substitution,DS)最高,达0.75。三种SCHP的总糖、糖醛酸含量和分子量大小较CHP都有所降低,单糖摩尔含量也有所改变,热稳定性略微减弱(多糖降解温度分别由CHP的211.17℃和282.01℃降低到SCHP的194.86~207.70℃和233.35~262.46℃)。体外抗氧化实验结果显示,SCHP对DPPH和羟基自由基的清除活性都低于CHP,且DS越大,活性降低程度越明显;而对ABTS~+自由基的清除能力和亚铁离子螯合能力而言,增加DS却可以提高其活性,8 mg/mL时,SCHP-2对ABTS^(+)自由基的清除率(54.82%)和亚铁离子的螯合率(15.59%)显著(P<0.05)高于CHP(33.67%和8.86%)。研究结果可为椰子吸器多糖的改性修饰和功能化应用提供支撑。

To investigate the effect of sulfated modification on the structure and function of coconut haustorium polysaccharide(CHP),three kinds of sulfated coconut haustorium polysaccharides(SCHP-2,SCHP-3,and SCHP-4)were prepared using sulfation reagents containing different ratios of chlorosulfonic acid and pyridine(v/v,mL/mL:1/2,1/3,and 1/4)after extracting CHP from the raw materials of coconut haustorium,and their basic chemical compositions,structural characteristics and antioxidant activity in vitro were compared and analyzed.Results showed that all three sulfation reagents were able to modify CHP(characteristic peaks of S=O and C-O-S were observed near 1100~1250 cm^(-1) and 820 cm^(-1) in infrared spectra,respectively),and the degree of substitution(DS)was the highest(0.75)at the ratio of chlorosulfonic acid and pyridine for 1/2.The total sugar,uronic acid content,and molecular weight of the three SCHP decreased,and the molar content of monosaccharides also changed when comparing with that of CHP.The thermal stability had slightly weakened as well(the degradation temperature of polysaccharides decreased from 211.17℃ and 282.01℃ of CHP to 194.86~207.70℃ and 233.35~262.46℃ of SCHP,respectively).The results of antioxidant experiments in vitro showed that the scavenging activity of SCHP on DPPH and hydroxyl radicals was lower than that of CHP,and the larger the DS was,the more obvious the decrease in activity was.In terms of the ABTS+radicals scavenging ability and ferrous ions chelating activity,increasing DS could enhance the activity of SCHP.At 8 mg/mL,the ABTS+radicals scavenging rate(54.82%)and ferrous ions chelating rate(15.59%)of SCHP-2 were significantly(P<0.05)higher than CHP(33.67% and 8.86%).These results would provide the support for the modification and functional application of coconut haustorium polysaccharides.