Jones L H
Am J Clin Nutr. 1978 Oct;31(10 Suppl):S94-S98. doi: 10.1093/ajcn/31.10.S94.
Plant cell walls that are secondarily thickened contain silicon and metal cations. The silicon occurs predominantly as silica (SiO2.nH2O) deposited in intimate association with the organic components of the walls and, according to recent evidence, as an integral constituent of polyuronides. Relatively large amounts of deposited (i.e., solid) silica are found in rice and other cereals and in grasses. When ingested by ruminant animals, practically all the solid silica may be recovered in the feces. However, microscopic particles of silica from plants are, to a small extent, absorbed as such through the gastrointestinal wall in both man and ruminant animals. It has now been shown that silicon is essential for animals, and that it is a constituent of certain mucopolysaccharides, thereby contribution to the architecture of connective tissues. The acidic silanol group of solid silica in plant cell walls may be involved in binding metal cations, but carboxyl and phenolic hydroxyl groups of the organic components of the walls are probably mainly responsible. Binding of metal cations by these components of plant cell walls, and possibly by silica, is likely to reduce availability of the cations for intestinal absorption.
次生加厚的植物细胞壁含有硅和金属阳离子。硅主要以二氧化硅（SiO₂·nH₂O）的形式存在，与细胞壁的有机成分紧密结合沉积，并且根据最近的证据，它还是聚糖醛酸的一个组成部分。在水稻和其他谷物以及禾本科植物中发现了相对大量的沉积（即固态）二氧化硅。反刍动物摄入后，几乎所有的固态二氧化硅都可以在粪便中回收。然而，来自植物的二氧化硅微粒在人和反刍动物中会有少量原样通过胃肠壁被吸收。现已表明，硅对动物是必需的，并且它是某些粘多糖的组成部分，从而对结缔组织的结构有贡献。植物细胞壁中固态二氧化硅的酸性硅醇基团可能参与结合金属阳离子，但细胞壁有机成分的羧基和酚羟基可能起主要作用。植物细胞壁的这些成分以及可能还有二氧化硅对金属阳离子的结合，可能会降低阳离子被肠道吸收的可用性。
