Chemical modification, characterization and bioactivity of Chinese lacquer polysaccharides from lac tree Rhus vernicifera against leukopenia induced by cyclophosphamide

Lacquer polysaccharide (LP) was isolated from the sap of lac tree (Rhus vernicifera). Its derivatives, carboxymethyl LP, sulfated LP and debranching LP were prepared. Their structure was analyzed by GPC, FT-IR and NMR spectroscopy. The sugar components of carboxymethyl and sulfated LPs hardly changed, but the molecular weight of the former decreased. The side chains of LPs were partially removed using sodium periodate in mild conditions and the pyranose ring β-configuration of products obtained was not changed. Bioactivity of natural and modified LPs against leukopenia induced by cyclophosphamide (CP) was investigated in mice. LP exhibited a significant bioactivity (P<0.05) compared to positive control group (CP). The bioactivity could increase slightly with the increasing of the contents of carboxymethyl groups. However, with the removal of the side chains and the incorporation of sulfate groups, the bioactivity gradually decreased. These showed that the bioactivity of lacquer polysaccharides against leukopenia induced by CP was strongly dependent on the types of ionic groups of the polysaccharides and concerned with the side chains with 4-O-methyl-β-glucuronic acid in the terminal.