Yong Wei Cong Matthew, Devi Apramita, Lin Tsair-Fuh, Chappell Helen F
School of Food Science and Nutrition, University of Leeds, Leeds, UK.
Department of Viticulture and Enology, University of California, Davis, CA, USA.
NPJ Sci Food. 2024 May 14;8(1):28. doi: 10.1038/s41538-024-00270-1.
Finger millet, a cereal grain widely consumed in India and Africa, has gained more attention in recent years due to its high dietary fibre (arabinoxylan) and trace mineral content, and its climate resilience. The aim of this study was to understand the interactions between potassium (K), calcium (Ca) and zinc (Zn) ions and the arabinoxylan structure and determine its ion-binding capacity. Three variations of a proposed model of the arabinoxylan structure were constructed and first principles Density Functional Theory calculations were carried out to determine the cation-binding capacity of the arabinoxylan complexes. Zn-arabinoxylan complexes were highly unstable and thermodynamically unfavourable in all three models. Ca and K ions, however, form thermodynamically stable complexes, particularly involving two glucuronic acid residues as a binding pocket. Glucuronic acid residues are found to play a key role in stabilising the cation-arabinoxylan complex, and steric effects are more important to the stability than charge density. Our results highlight the most important structural features of the millet fibre regarding ion-storage capacity, and provide valuable preliminary data for confirmatory experimental studies and for the planning of clinical trials where the bioavailability of bound ions following digestion may be tested.
龙爪稷是一种在印度和非洲广泛食用的谷物，近年来因其高膳食纤维（阿拉伯木聚糖）和微量矿物质含量以及气候适应能力而受到更多关注。本研究的目的是了解钾（K）、钙（Ca）和锌（Zn）离子与阿拉伯木聚糖结构之间的相互作用，并确定其离子结合能力。构建了阿拉伯木聚糖结构的一个提议模型的三种变体，并进行了第一性原理密度泛函理论计算，以确定阿拉伯木聚糖复合物的阳离子结合能力。在所有三种模型中，锌 - 阿拉伯木聚糖复合物都高度不稳定且在热力学上不利。然而，钙和钾离子形成热力学稳定的复合物，特别是涉及两个葡萄糖醛酸残基作为结合口袋。发现葡萄糖醛酸残基在稳定阳离子 - 阿拉伯木聚糖复合物中起关键作用，并且空间效应比电荷密度对稳定性更重要。我们的结果突出了小米纤维在离子储存能力方面最重要的结构特征，并为验证性实验研究以及规划临床试验提供了有价值的初步数据，在临床试验中可以测试消化后结合离子的生物利用度。
