Preparation, characterization and antioxidant activity of polysaccharides selenides from Qingzhuan Dark Tea

The effective selenylated polysaccharides (refer as TPS-Se) with an average molecular weight (M_W) of 3.109 × 104 Da was synthesized by the reduction of sodium selenite with ascorbic acid in the presence of Qingzhuan Dark Tea polysaccharides (TPS). The selenium (Se) content of TPS-Se was up to 37.05%. The differences between TPS and TPS-Se were compared in morphology, structure, antioxidant activity, and molecular weight using FT-IR, Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), SEM, AFM, and Integrated thermal gravimetric analysis. The results indicated that Se⁴⁺ was reduced to Se⁰ by ascorbic acid. Further, the Se⁰ atoms aggregate into Se nuclei and bind to the C=O from TPS. Also, TPS-Se exhibited higher DPPH and ABTS radical-scavenging abilities than TPS. This difference may be attributed to the fact that Se has good antioxidant activity. The test results demonstrated that TPS-Se was prepared successfully by reducing sodium selenite with ascorbic acid, which exhibited a higher radical-scavenging ability. Finally, LD₅₀ value of 136.89 mg/kg, with a 95% confidence interval of 102.82~182.82 mg/kg, was determined by gavage administration for TPS-Se's. Practical Application: Develop Qingzhuan Dark Tea for pharmaceutical industry. (author)