酚酸结构对酚酸-g-聚甘露糖醛酸抗氧化性能的影响

Effect of phenolic acid structure on antioxidant activity of phenolic acid-g-polymanturonic acid

海藻酸钠水解产物聚甘露糖醛酸(PM)的羧基与乙二胺(EDA)的一个氨基反应制得了中间体PM-EDA,PM-EDA分别与8种酚酸(PA)接枝共聚,制得了8种接枝共聚物酚酸-g-聚甘露糖醛酸(PA-g-PM)。对PM-EDA的制备条件进行了优化,探究了PA结构对PA-g-PM抗氧化活性的影响。结果表明,在n(PM)∶n(EDA)=1∶1.5,n(PM)∶n(碳二亚胺)∶n(N-羟基琥珀酰亚胺)=1∶2∶1,pH 8.0条件下反应24 h,获得最高取代度(17.27%)的PM-EDA。8种PA-g-PM的接枝率在(4.171±0.16)~(8.880±0.32)mg没食子酸/g之间。UV-Vis、FTIR、XRD表征证实酚酸已成功接枝到PM上。相比于PM,8种PA-g-PM对1,1-二苯基-2-三硝基苯肼(DPPH)自由基的清除率和对铁的还原力均显著提升。PA-g-PM的抗氧化性能与其中的酚羟基个数呈正相关关系,含有对位酚羟基的PA-g-PM的抗氧化性能优于含有邻位酚羟基的PA-g-PM的抗氧化性能,PA-g-PM中的酚羟基被甲氧基取代后抗氧化性能减弱。

Eight kinds of graft copolymers phenolic acid-g-polymanturonic acid(PA-g-PM)were prepared by graft copolymerization of eight phenolic acids(PA)and intermediate PM-EDA,which was synthesized from the reaction between the carboxy group of polymanuronic acid(PM),a hydrolysate of sodium alginate,and the amino group of ethylenediamine(EDA).The preparation conditions of PM-EDA were optimized,and the influence of PA structure on the antioxidant activities of PA-g-PM were investigated.The results showed that under the conditions of n(PM)∶n(EDA)=1∶1.5,n(PM)∶n(carbodiimide)∶n(N-hydroxysuccinimide)=1∶2∶1,pH 8.0,and reaction time of 24 h,PM-EDA with the highest substitution degree of 17.27%was obtained.Data from UV-Vis,FTIR and XRD analyses showed that phenolic acids were successfully graft onto PM,with grafting rates ranging from(4.171±0.16)to(8.880±0.32)mg gallic acid/g for the eight copolymers.Compared with PM,all eight PA-g-PM copolymers exhibited significantly enhanced 1,1-diphenyl-2-picrylhydrazyl(DPPH)scavenging rate and iron reducing power.The antioxidant performance of PA-g-PM was positively correlated with the number of phenolic hydroxyl groups contained,with that of PA-g-PM possessing para-phenolic hydroxyl group superior to that of possessing ortho-phenolic hydroxyl group.Meanwhile,PA-g-PM with methoxy group in replacement of phenolic hydroxyl group showed weakened antioxidant activity.