Structural characterization and anti-proliferative activities of partially degraded polysaccharides from peach gum

LP100R, LP10R and LP5R were isolated from peach gum by ultrafiltration. They were identified as AG II arabinogalactans composed of mannose, rhamnose, glucuronic acid, galactose, xylose and arabinose, which had a beta-D-(1 -> 6)-galactan backbone and were branched at O-3 and O-4. LP100R, LP10R and LP5R exist in a spherical conformation with the molecular weight of 8.50 x 10(4) g/mol, 4.77 x 10(4) g/mol and 2.40 x 10(4) g/mol, respectively. The binding affinities of LP fractions to galectin-3 (Gal-3) were 0.77 mu M for LP100R, 2.88 mu M for LP10R and 5.15 mu M for LP5R, respectively. Meanwhile, an anti-proliferative assay revealed that LP100R possessed higher anti-proliferative activity against HepG2 cells (IC50, 4.5 mg/mL) and MCF-7 cells (IC50, 0.43 mg/mL) than did LP10R and LP5R, which were in accordance with their binding affinities to galectin-3. Therefore, LP fractions (especially LP100R) might exert the anti-tumor activity by directly inhibiting the Gal-3 mediated proliferation of cancer cells.