Antioxidant activities of an exopolysaccharide isolated and purified from marine Pseudomonas PF-6

► An acidic polysaccharide from marine Pseudomonas PF-6 was obtained. ► The EPS had some scavenging action on DPPH·, ·OH and O2−·. ► High content of uronic acid in acidic EPSs may be the main effect on radical scavenging activity. ► The acidic EPS from marine Pseudomonas PF-6 had potentials as a natural antioxidant. An acidic exopolysaccharide (EPS) was isolated and purified from marine Pseudomonas PF-6. The test of physical properties indicated that the EPS was odorless, soluble in water, insoluble in organic solvents, and had a molecular weight of 8.83×105Da. The test of chemical properties of the EPS showed that the EPS could be oxidized into uronic acid. Infrared spectrometry analysis exhibited absorption bands at 927.49cm−1 and 811.76cm−1, suggesting that the EPS belonged to a β-type heteropolysaccharide with a pyran group. Several in vitro assays were applied to evaluate the antioxidant potential of the EPS. Results showed that the acidic EPS had scavenging actions on DPPH·, ·OH and O2−· and the antioxidant activities increased with increases in its concentration. The scavenging action of the EPS on ·OH was stronger than that of Vc, and its activity on O2−· was almost the same as that of Vc.