Chemical modification and antitumour activity of Chinese lacquer polysaccharide from lac tree Rhus vernicifera

Lacquer polysaccharide from Rhus vernicifera was separated into two fractions with high and low molecular weights, LPH and LPL. LPL was degraded using dilute sulphuric acid. Besides molecular weight, products had only a little change in their contents of α-l-rhamnopyranose, α-l-arabinofuranose and α-d-galactopyranose. The side chains of LPH and LPL were partially removed with NaIO4 oxidation. The structures of all polysaccharides were investigated by GPC, FT-IR, 1H and 13C NMR spectroscopy. S-180 ascites tumour in mice was used to assay the antitumour activity of lacquer polysaccharide and its derivatives using two doses (150 and 300 mg/kg/d). The antitumour activity was related to Mw and the branching structure of polysaccharide. Natural polysaccharides had significant activity, and LPL had the highest activity, its inhibitory rate by intraperitoneal injection for 7 d using a 150 mg/kg/d dose reached 63.5%. Decrease of Mw and removal of side chains led to reduction or loss of antitumour activity. Experimental results also showed that the low dose group had higher activity, and the bloody ascites was prevented by the polysaccharide groups.