Preparation and biological evaluation of a novel selenium-containing exopolysaccharide from Rhizobium sp. N613

• A novel Se-REPS was synthesized and the preparation conditions were optimized.
• Se-REPS exhibits strong antitumor efficacy both in vitro and in vivo.
• Se-REPS could obviously elevate the thymus and spleen indices in tumor-bearing mice.

In order to obtain a low toxic antitumor agent and an organic selenium source, an exopolysaccharide obtained from Rhizobium sp. N613 (REPS) was modified by selenious acid using barium chloride as the catalyst. The reaction conditions were optimized by response surface methodology (RSM), and the optimal conditions for preparation of selenium-containing REPS (Se-REPS) were obtained. The selenium content of Se-REPS was 790 μg/g under these conditions. The molecular structure of Se-REPS was confirmed by FTIR. In vitro antitumor activity of Se-REPS was evaluated by MTT assay, and the results indicated that Se-REPS could significantly inhibit the growth of S180 and HepG2 cells. Furthermore, Se-REPS exhibited comparable in vivo antitumor efficacy to cyclophosphamide at same concentrations. In addition, Se-REPS could substantially elevate the thymus and spleen indices in tumor-bearing mice. This study demonstrates that Se-REPS holds great potential to be a desirable antitumor agent for therapeutic and immunomodulatory applications.