Structural characterization and bioactivity of released exopolysaccharides from Lactobacillus plantarum 70810

Two released exopolysaccharides (r-EPS1 and r-EPS2) were isolated from the culture supernatant of Lactobacillus plantarum 70810 by ethanol precipitation, anion exchange and gel filtration chromatography and characterization of the structures were conducted. The r-EPS1 and r-EPS2 were homogenous polysaccharides with average molecular weights of, respectively, 204.6 and 202.8 kDa, and composed of glucose, mannose and galactose with molar ratios of 18.21:78.76:3.03 and 12.92:30.89:56.19, respectively. Methylation and NMR analysis revealed r-EPS1 was consisted of alpha configuration sugar residues, whereas r-EPS2 contained both alpha and beta configuration sugar residues. Antioxidant and antitumor activities of the two exopolysaccharides were evaluated in vitro. The results showed that r-EPS1 and r-EPS2 exhibited potent antioxidant activities regarding hydroxyl and DPPH radicals scavenging and reducing power assays, and possessed antitumor activities against Caco-2, BGC-823 and HT-29 cells, which suggested that they could be potential sources of antioxidant and antitumor drug.