Preparation, characterization and bioactivities of derivatives of an exopolysaccharide from Lachnum.

An exopolysaccharide, obtained previously LEP-2b from Lachnum YM405, was phosphated and sulfated successfully. The derivatives named PLEP-2b and SLEP-2b, respectively, and their respective degree of substitution were 0.174 and 0.431. Phosphate groups -PO3H2 substituted at C-6 of 1,4-β-D-mannopyranose, C-5 of 2,6-β-d-1-OMe-mannofuranoside, C-3 of 1,6-β-D-galactopyranose, C-2 of 1-β-D-glucopyranose, and C-6 of 1,2-α-D-rhampyranose, while sulfate groups SO3H were mainly at C-6 of 1,4-β-D-Manp, C-6 of 1-β-D-Glcp and C-6 of 1,2-α-D-Rhap. Compared with LEP-2b, the scavenging effects of the derivatives, on hydroxyl radical and superoxide anion were significantly increased after the modifications, except for reducing power. Meanwhile, phosphorylated and sulfated modifications remarkably strengthened the inhibiting effect of LEP-2b on the proliferation of CT-26 murine colon carcinoma, Lewis lung carcinoma and human hepatocellular carcinoma HepG2 cells. The derivatives significantly enhanced the antioxidant and antitumor activities in vitro. Compared with sulfation, phosphorylation improved the inhibitory effect more contraposingly on some specific tumor cells.