Microwave-assisted synthesis, structure and anti-tumor activity of selenized Artemisia sphaerocephala polysaccharide

In this work, selenylation of Artemisia sphaerocephala polysaccharide (SeASP_MW) was studied by using H₂SeO₃/HNO₃/BaCl₂ reaction system in microwave field. SeASP_MW exhibited the Se content range of 111-264μg/g with high yields (72.1-94.9%). ¹³C NMR results indicated that the weak C-6 substitution was occurred. The decrease (from 7.348×10⁴g/mol to 1.736-4.667×10⁴g/mol) in weight average molecular mass (M_W) of SeASP_MW was observed in size exclusion chromatography combined with multi angle laser light scattering (SEC-MALLS) analysis. SeASP_MW exhibited a more rigid solution conformation which might be due to the degradation of polysaccharide chains in acidic reaction reagent. This was also supported by atomic force microscopy (AFM) result that SeASP_MW showed short chains and island-like topography. In anti-tumor activity assays, SeASP_MW6 exhibited the inhibition rates of 32.381% and 39.776% against human non-small cell lung cancer cell line (H1650) at the concentration of 100 and 200μg/mL, respectively. The relatively weak inhibition effect of SeASP_MW was not related to cell apoptosis and cell cycle arrest, suggesting Se content might be a key factor to influence the anti-tumor activities of selenized polysaccharides in vitro.