Marlett Judith A, Fischer Milton H
Department of Nutrition Sciences, University of Wisconsin-Madison, Wisconsin 53706, USA.
Proc Nutr Soc. 2003 Feb;62(1):207-9. doi: 10.1079/pns2002201.
A series of experiments and evaluations of fractions isolated from psyllium seed husk (PSH) were used to test the overall hypothesis that a gel-forming component of PSH is not fermented and that it is this component that is responsible for the laxative and cholesterol-lowering properties of PSH. A gel is isolated from human stools collected during a controlled diet study when PSH is consumed but not when the control diet only is consumed. Evaluations of three fractions isolated from PSH suggest that gel-forming fraction B, which is about 55% of PSH, is poorly fermented and is the component that increases stool moisture and faecal bile acid excretion, the latter leading to lower blood cholesterol levels. Fraction C, representing < 15% of PSH, is viscous, but is rapidly fermented. Fraction A is alkali-insoluble material that is not fermented. In concentrations comparable with their presence in PSH, fractions A and C do not alter moisture and bile acid output. The active fraction of PSH is a highly-branched arabinoxylan consisting of a xylose backbone and arabinose- and xylose-containing side chains. In contrast to arabinoxylans in cereal grains that are extensively fermented, PSH possesses a structural feature, as yet unidentified, that hinders its fermentation by typical colonic microflora.
对从洋车前子壳（PSH）中分离出的各组分进行了一系列实验和评估，以检验总体假设：PSH的一种凝胶形成成分不会被发酵，正是该成分赋予了PSH通便和降胆固醇特性。在一项对照饮食研究中，当食用PSH时，可从收集的人类粪便中分离出凝胶，而仅食用对照饮食时则无法分离出凝胶。对从PSH中分离出的三个组分的评估表明，占PSH约55%的凝胶形成组分B发酵程度低，且是增加粪便水分和粪便胆汁酸排泄的成分，后者可降低血液胆固醇水平。占PSH不到15%的组分C具有粘性，但发酵迅速。组分A是不溶于碱且不被发酵的物质。在与它们在PSH中的存在浓度相当的情况下，组分A和C不会改变水分和胆汁酸的排出量。PSH的活性组分是一种高度分支的阿拉伯木聚糖，由木糖主链以及含阿拉伯糖和木糖链的侧链组成。与谷物中被广泛发酵的阿拉伯木聚糖不同，PSH具有一种尚未确定的结构特征，可阻碍其被典型的结肠微生物群发酵。
