Institute of Bioscience, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
Faculty of Applied Sciences and Computing, Tunku Abdul Rahman University College, 53300 Kuala Lumpur, Malaysia.
Molecules. 2014 Jun 12;19(6):7990-8010. doi: 10.3390/molecules19067990.
Condensed tannins (CTs) form insoluble complexes with proteins and are able to protect them from degradation, which could lead to rumen bypass proteins. Depending on their degrees of polymerization (DP) and molecular weights, CT fractions vary in their capability to bind proteins. In this study, purified condensed tannins (CTs) from a Leucaena leucocephala hybrid were fractionated into five different molecular weight fractions. The structures of the CT fractions were investigated using 13C-NMR. The DP of the CT fractions were determined using a modified vanillin assay and their molecular weights were determined using Q-TOF LC-MS. The protein-binding affinities of the respective CT fractions were determined using a protein precipitation assay. The DP of the five CT fractions (fractions F1-F5) measured by the vanillin assay in acetic acid ranged from 4.86 to 1.56. The 13C-NMR results showed that the CT fractions possessed monomer unit structural heterogeneity. The number-average molecular weights (Mn) of the different fractions were 1265.8, 1028.6, 652.2, 562.2, and 469.6 for fractions F1, F2, F3, F4, and F5, respectively. The b values representing the CT quantities needed to bind half of the maximum precipitable bovine serum albumin increased with decreasing molecular weight--from fraction F1 to fraction F5 with values of 0.216, 0.295, 0.359, 0.425, and 0.460, respectively. This indicated that higher molecular weight fractions of CTs from L. leucocephala have higher protein-binding affinities than those with lower molecular weights.
缩合单宁（CT）与蛋白质形成不溶性复合物，并能够保护它们免受降解，从而导致瘤胃旁路蛋白。根据其聚合度（DP）和分子量的不同，CT 级分结合蛋白质的能力也不同。在这项研究中，从 Leucaena leucocephala 杂种中分离出的纯化缩合单宁（CT）被分为五个不同的分子量级分。使用 13C-NMR 研究 CT 级分的结构。使用改良的香草醛测定法测定 CT 级分的 DP，并使用 Q-TOF LC-MS 测定其分子量。使用蛋白质沉淀测定法测定各自 CT 级分的蛋白质结合亲和力。通过香草醛测定法在乙酸中测量的五个 CT 级分（级分 F1-F5）的 DP 范围为 4.86 至 1.56。13C-NMR 结果表明，CT 级分具有单体单元结构异质性。不同级分的数均分子量（Mn）分别为 1265.8、1028.6、652.2、562.2 和 469.6，分别为级分 F1、F2、F3、F4 和 F5。表示结合半最大可沉淀牛血清白蛋白所需 CT 量的 b 值随分子量的降低而增加 - 从级分 F1 到级分 F5，值分别为 0.216、0.295、0.359、0.425 和 0.460。这表明来自 L. leucocephala 的较高分子量 CT 级分比具有较低分子量的级分具有更高的蛋白质结合亲和力。
