Structural Elucidation of a Novel Pectin-Polysaccharide from the Petal of Saussurea Laniceps and the Mechanism of Its Anti-HBV Activity

A novel polysaccharide designated SLP-4 with the Mw of 19681 Da was purified from the petal of Saussurea laniceps. Monosaccharide composition analysis indicated that SLP-4 was composed of mannose, rhamnose, galacturonic acid, glucose, galactose, xylose and arabinose in a molar ratio of 0.825:2.030:14.998:0.841:8.260:4.039:6.009. Structural features indicated that SLP-4 was a typical pectin polysaccharide with a backbone containing →3,6)-Galp-(1→, →4)-GalpA-(1→, →6)-Galp-(1→, →4, 6)-Galp-(1→ and →2, 4)-Rhap-(1→ with the branches of →4)-Galp-(1→, T-Galp-(1→, →3)-Galp-(1→, T-Rhap-(1→, T-Araf-(1→, →5)-Araf-(1→, T-Glcp-(1→, →4)-Xylp-(1→ and →4)-Manp-(1→. Additionally, SLP-4 could effectively inhibit the secretion of HBsAg and HBeAg in HepG2.2.15 cells, but had little effect on the replication of HBV DNA. This inhibition didn't involve cellular pathways, and was due to the interaction between SLP-4 and HBsAg or HBeAg, which may block the ELISA detection of HBsAg and HBeAg. The present study may provide useful information for further study of SLP-4 and understanding of anti-HBV activity of polysaccharides.