Enhanced physicochemical, rheological and antioxidant properties of highly succinylated succinoglycan exopolysaccharides obtained through succinic anhydride esterification reaction.

Highly succinylated succinoglycan (HS-SG) was prepared by reacting succinic anhydride with succinoglycan (SG) exopolysaccharide isolated from Sinorhizobium meliloti. The rheological, physicochemical properties, and antioxidant effects of HS-SG were evaluated in comparison with SG. NMR and FTIR analyses confirmed that HS-SG retained the characteristic glycosidic structure of SG while showing a relative increase in succinyl functional groups. DSC analysis revealed that HS-SG 50, with a reaction molar ratio of SG to succinic anhydride of 1:50, exhibited a higher endothermic peak at 151 °C, indicating improved thermal stability compared to SG's peak at 93 °C. Rheological analysis demonstrated that HS-SG 50 had a viscosity 250 % higher than SG at a shear rate of 10 s. Unlike SG, whose viscosity dropped to less than 1 % above 60 °C, HS-SG 50 maintained about 30 % viscosity at the same temperature. Additionally, HS-SG 50 showed significantly enhanced antioxidant activity in DPPH and hydroxyl radical scavenging tests and was non-toxic in a cytotoxicity test using HEK-293 cells. These findings suggest that highly succinylated succinoglycan exhibits improved thermal stability, viscosity, and antioxidant properties, making it a promising biomaterial for applications in cosmetics, pharmaceuticals, biomedicine, and polysaccharide-based biotechnology.