Chemical characterization and antioxidant activity of an exopolysaccharide fraction isolated from Bifidobacterium animalis RH

The major exopolysaccharide fraction (EPSa) of Bifidobacterium animalis RH was purified to illustrate the chemical characterization and the antioxidant activity in vitro. The molecular weight of EPSa was 2.31 x 10(4) Da determined by the gel permeation chromatography (GPC). Fourier-transform infrared spectra (FT-IR) and the monosaccharide analysis of high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) showed that it was a heteropolysaccharide mainly composed of d-glucose, d-mannose, d-galactose, l-arabinose, d-fructose, and l-rhamnose in molar ratios of 43:34:18:4:1:1. In antioxidant assays, the EPSa had a higher activity for antilipid peroxidation and a stronger scavenging activity of hydroxyl radical and superoxide radical than ascorbic acid. It also had a similar alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) radical-scavenging activity with ascorbic acid at low concentration and had concentration-dependent inhibitory ability on erythrocyte hemolysis. These results indicated that the EPSa fraction had strong antioxidant activities and could be explored as novel potential antioxidants.