Structural features and biological activity of an acidic polysaccharide complex from Mahonia aquifolium (Pursh) Nutt

The crude hemicelluloses, isolated from stems of Mahonia aquifolium, on ion-exchange and gel chromatography gave an acidic polysaccharide (AP) which eluted as a broad band in high-pressure gel-permeation chromatography. The average apparent molecular mass (Mapp) was determined to be 5.8 kDa. Compositional and linkage analyses, supported by 1D and 2D NMR spectroscopy measurements of the polysaccharide before and after modification using partial acid hydrolysis and digestion with pectinase led to the conclusion that AP was a complex of two closely associated polysaccharides. The first was a (4-O-methylglucurono)xylan with the molar ratio Xyl/MeGlcA=6.7 and the second one a pectin with a very low proportion of neutral side chains. The pectin component contained homogalacturonan and rhamnogalacturonan RG-I regions in the ratio of about 2:1. Though the HMBC spectrum of AP indicated that some of the xylan chains might be linked to GalA of PGA, unequivocal proof for the existence of the linkage was not found. When tested for antitussive activity on a mechanically induced cough in cats, AP exhibited a pronounced cough-suppressive effect, much higher than that of some drugs used in clinical practice. The polysaccharide also showed mitogenic and comitogenic activities comparable to those of the commercial immunomodulator Zymosan—a beakerʹs yeast β-glucan.