School of Chemical Engineering, Xiangtan University, Xiangtan 411105, Hunan, China
海藻酸鈉水解產物聚甘露糖醛酸（PM）的羧基與乙二胺（EDA）的一個氨基反應制得了中間體 PM-EDA， PM-EDA 分別與 8 種酚酸（PA）接枝共聚，制得了 8 種接枝共聚物酚酸-g-聚甘露糖醛酸（PA-g-PM）。對 PM-EDA 的制備條件進行了優化，探究了 PA 結構對 PA-g-PM 抗氧化活性的影響。結果表明，在 n(PM)∶n(EDA)=1∶1.5， n(PM)∶n（碳二亞胺）∶n（N-羥基琥珀酰亞胺）=1∶2∶1，pH 8.0 條件下反應 24 h，獲得最高取代度（17.27%） 的 PM-EDA。8 種 PA-g-PM 的接枝率在（4.171±0.16）~（8.880±0.32） mg 沒食子酸/g 之間。UV-Vis、FTIR、 XRD 表征證實酚酸已成功接枝到 PM 上。相比于 PM，8 種 PA-g-PM 對 1,1-二苯基-2-三硝基苯肼（DPPH）自由 基的清除率和對鐵的還原力均顯著提升。PA-g-PM 的抗氧化性能與其中的酚羥基個數呈正相關關系，含有對位 酚羥基的 PA-g-PM 的抗氧化性能優于含有鄰位酚羥基的 PA-g-PM 的抗氧化性能，PA-g-PM 中的酚羥基被甲氧基 取代后抗氧化性能減弱。
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.