Synthesis, Structural Characterization and In Vitro Immunosuppressive Activity of Quinoa Bran Soluble Dietary...

The biological effects of dietary fiber (DF) are often associated with its chemical structure and interactions with the immune system. In this study, soluble DF (SDF) from quinoa bran was modified via gallium ion (Ga³⁺) chelation to form SDF-Ga. Results showed that gallium chelation reduced molecular weight, homogenized the polymer, and increased chain branching, forming a compact three-dimensional network. The cytotoxicity of HCT-116 colorectal cancer cells mediated by NK cells was significantly influenced by SDF-Ga, reaching 45.32% at 100 μg/mL. Key immune factors exhibited notable upregulation. Co-culture assays indicated that SDF-Ga inhibited cancer cell proliferation and migration (p < 0.01). In vitro assays suggested a concentration-dependent inhibition of HCT-116 cell viability, exhibiting enhanced anticancer potential compared with unmodified SDF. In summary, our results highlight that gallium chelation is an effective strategy to improve the functional properties of dietary fibers. The dual immunomodulatory and anticancer activities of the SDF-Ga complex position it as a valuable candidate for the development of novel nutraceuticals and health-promoting food products.