Characterization of the structure and properties of carboxymethyl sesbania gum and its antioxidant activity...

Carboxymethylation is a widely recognized method for modifying galactomannans, often employed to enhance their solubility, stability, and biological activities. In this study, carboxymethyl sesbania gum (CMSG) was synthesized under different reaction conditions, and the influence of these conditions on the degree of substitution was systematically assessed. Alkaline conditions were crucial for carboxymethylation, with reaction temperature, time, and etherifying agent concentration significantly affecting the degree of substitution. The maximum degree of substitution of 0.91 was achieved using an alkali molar ratio of 6.885 and an etherifying agent ratio of 3.43, under either 60 °C for 4 h or 50 °C for 9 h, following alkalization at 30 °C for 1 h. Structural analysis confirmed successful modification and revealed non-selective carboxymethyl group substitution, along with a reduction in molecular weight and thermal stability due to hydrogen bond disruption. Notably, CMSG demonstrated enhanced protective effects on Caco-2 cells; higher degrees of substitution correlated with superior antioxidant activity. This improved activity is attributed to lower molecular weight and increased charge density, leading to elevated intracellular superoxide dismutase and glutathione peroxidase levels, consequently reducing reactive oxygen species and lipid peroxidation. These findings highlight the potential of CMSG as a functional biomaterial with enhanced antioxidant properties.