Relationship between structural properties and antitumor activity of Astragalus polysaccharides extracted with different temperatures

This study investigated the effects of different temperatures on structural characterization and antitumor activity of polysaccharides from Astragalus membranaceus. APS4 and APS90 were extracted at 4°C and 90°C, respectively, and purified by Sephadex G-200 column. APS4-90 were obtained from APS4 after treatment at 90°C for 6h. MTT results showed that APS4 possessed the highest inhibitory effects on MGC-803, A549 and HepG2 cells. HPGPC analysis showed that the average molecular weights of these polysaccharides were approximately 1.5×106Da, while the asymmetrical peak of APS4-90 suggested heat degradation and configuration changes of APS4. GC, NMR and methylation results showed that these three polysaccharides had similar monosaccharide components (mainly contain glucose), and their backbones were composed of (1→2)‑α‑d‑Glcp. However, APS4 showed higher content of (1→2,6)‑α‑d‑Glcp compared to APS4-90 and APS90, which indicated that higher branched degree would be responsible for the stronger in vitro antitumor activity in APS4. These results were also confirmed by specific rotation and SEM analysis. Our study suggested that APS4 had the potential application for cancer treatment.