Zhang Guoguang, Huang Bingqing, Zheng Chenmin, Chen Qiaoling, Fei Peng
Key Laboratory of Landscape Plants with Fujian and Taiwan Characteristics of Fujian Colleges and Universities, School of Biological Science and Biotechnology, Minnan Normal University, Zhangzhou 363000, P. R. China.
J Agric Food Chem. 2021 Feb 3;69(4):1234-1241. doi: 10.1021/acs.jafc.0c06120. Epub 2020 Dec 10.
This study presents a method for modifying pectin with phenolic acids catalyzed by lipase in a two-phase system of water/tetrahydrofuran. Salicylic acid (SA) and its isomers, including -hydroxybenzoic acid (MHBA) and -hydroxybenzoic acid (PHBA), were grafted onto pectin, and the products were characterized via UV-vis, Fourier transform infrared spectroscopy (FTIR), and H NMR analyses to explore the reaction process and mechanism between pectin and the three phenolic acids. Results indicated that lipase played a dual role in the reaction, namely, catalyzing the hydrolysis of the methyl group in the aqueous phase and esterifying the carboxyl group of pectin with the phenolic hydroxyl group of the phenolic acids in tetrahydrofuran. The grafting ratio of SA-modified pectin, MHBA-modified pectin, and PHBA-modified pectin was 1.89, 10.58, and 20.32%, respectively, and it was affected by the position of phenolic hydroxyl. Moreover, the effects of phenolic acids on the emulsifying properties, antioxidant activities, and antibacterial activities of the native and modified pectins were evaluated. In several aspects, the emulsifying properties of the modified pectins were better than those of native pectin. Moreover, the grafting of phenolic acids only slightly affected the 1,1-diphenyl-2-picryl hydrazine (DPPH) clearance of the modified pectins but substantially improved their inhibition ratio in a β-carotene bleaching assay. Furthermore, the modified pectins exhibited better bacteriostatic activity against both and than native pectin.
本研究提出了一种在水/四氢呋喃两相体系中，利用脂肪酶催化酚酸修饰果胶的方法。将水杨酸（SA）及其异构体，包括间羟基苯甲酸（MHBA）和对羟基苯甲酸（PHBA）接枝到果胶上，并通过紫外可见光谱、傅里叶变换红外光谱（FTIR）和核磁共振氢谱分析对产物进行表征，以探究果胶与这三种酚酸之间的反应过程和机理。结果表明，脂肪酶在反应中起双重作用，即在水相中催化甲基水解，在四氢呋喃中使果胶的羧基与酚酸的酚羟基酯化。SA修饰果胶、MHBA修饰果胶和PHBA修饰果胶的接枝率分别为1.89%、10.58%和20.32%，且受酚羟基位置的影响。此外，还评估了酚酸对天然果胶和改性果胶的乳化性能、抗氧化活性和抗菌活性的影响。在几个方面，改性果胶的乳化性能优于天然果胶。此外，酚酸的接枝对改性果胶的1,1-二苯基-2-苦基肼（DPPH）清除率影响较小，但在β-胡萝卜素漂白试验中显著提高了其抑制率。此外，改性果胶对大肠杆菌和金黄色葡萄球菌的抑菌活性均优于天然果胶。
