Objective: The aim of this study was to isolate and purify the polysaccharide from Plantaginis Semen and to analyse the monosaccharide composition of the polysaccharide. Method: The crude polysaccharide from hot water extraction was subject to remove protein and preliminary isolated through Amberlite FPA90-Cl-+Amberlite IRC-84

purified by DEAE-cellulose chromatography and Sephacryl S-400 chromatography

a polysaccharide fraction named Plantago depressa L. polysaccharide B10(PP-B10) was obtained. The structural characterization and purity of PP-B10 were identified by Ultraviolet-visible Spectrophotometry and fourier transform infrared spectroscopy (FTIR). The monosaccharide composition analyses of PP-B10 was conducted by PMP pre-column derivatization high performance liquid chromatography. Result: A acidic polysaccharide fraction in high purity named PP-B10 was obtained from Plantaginis Semen and it was mainly composed of mannose

ribose

galacturonic acid

galactose

xylose

arabinose and fucose. Conclusion: PP-B10 was a novel polysaccharide with new monosaccharide composition which was found in Plantaginis Semen.