Structural characterization and anti-A549 lung cancer cells bioactivity of a polysaccharide from Houttuynia cordata

A water-soluble pectic polysaccharide HCA4S1 was isolated from Houttuynia cordata and purified by DEAE Cellulose and Sephacryl S-300 column. HCA4S1 with an average molecular weight of 21.7 kDa mainly consisted of rhamnose, galacturonic acid, galactose, and arabinose. By using partial acid hydrolysis, methylation analysis, and NMR spectra, the structure of this polysaccharide is found to have a backbone consisting of 1,4-linked α‑d‑GalA and 1,2,4-linked α‑l‑Rha. The latter was substituted at C-4 position by 1,4 linked, 1,6-linked β‑Galp, or Teminal linked β‑Gal. Bioactivity test showed that this polysaccharide might inhibit the proliferation of A549 lung cancer cell by inducing cell cycle arrest and apoptosis. The expression of cleaved caspase 3 and cyclinB1 was observed to be upregulated after the treatment with this polysaccharide. Collectively, these results suggest that the pectin HCA4S1 from Houttuynia cordata is of potential value in the treatment of lung cancer, though the underlying mechanisms remain to be further confirmed.