Characterization of a novel exopolysaccharide with antitumor activity from Lactobacillus plantarum 70810

Three methods were used to prepare the cell-bound exopolysaccharides (c-EPS) of Lactobacillus plantarum 70810, and the maximum yield (64.17 mg/mL) was obtained by ultrasonic extraction. After anion exchange and gel filtration chromatography, the c-EPS was fractionated as a single peak with a molecular weight of 169.6 kD. Its structural characteristics were investigated by gas chromatography (GC), methylation, Fourier-transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) analysis. Based on obtained data, the novel c-EPS was found to be a galactan containing a backbone of α-D-(1→6)-linked galactcosyl, β-D-(1→4)-linked galactcosyl, β-D-(1→2,3)-linked galactcosyl residues and a tail end of β-D-(1→)-linked galactcosyl residues. Preliminary in vitro tests revealed that c-EPS significantly inhibited the proliferation of HepG-2, BGC-823, especially HT-29 tumor cells. Our results suggested that the c-EPS produced by L. plantarum 70810 might be suitable for use as functional foods and natural antitumor drugs.