柴胡由来のペクチン性多糖の構造と薬理活性

創薬科学-分子から個体への薬理学

抄録

Several pharmacological activities have been observed in pectic polysaccharides which were isolated from Chinese herbs containing Kampo medicines. We found two different bioactive pectic polysaccharides, bupleuran 2IIb and 2IIc, from the roots of Bupleurum falcatum. These bioactive pectic polysaccharides were comprised of an α (1→4) linked galacturonan region, a ramified region that consists of a rhamnogalacturonan core substituted neutral sugar chains as the side chains and a rhamnogalacturonan II (RG II)-like region containing unique sugars such as 3-deoxy-manno-2-octulosonic acid (KDO). In order to understand the pharmacological activity of pectic polysaccharides on the molecular level, we have elucidated the essential carbohydrate structure for the expression of each pharmacological activity and their mode of actions. The ramified region in bupleuran 2IIb induced Fc receptor up-regulation in macrophages by a mechanism dependent on an increase of intracellular Ca²⁺, followed by the enhancement of immune complex clearance, whereas bupleuran 2IIc, which mainly consists of a partially branched galacturonan region, showed potent anti-ulcer activity. The major mechanism of its mucosal protection was suggested to be due to anti-secretory activity on acid and pepsin, its ability to provide a protective coating and radical scavenging effect. The future problems were also discussed in order to develop pectic polysaccharides as medicines.