Abstract: Boiling-water extraction and a DEAE-Sepharose CL-6B column chromatography were used to isolate and purify the major polysaccharide DMA from Dioscorea nipponica. Purification and compositional analysis of DMA were carried with HPLC and GC-FID analysis.IR analysis,periodate oxidation-smith degradation, methylation analysis and NMR studies (¹H, ¹³C, ¹H-¹H COSY and HSQC) were used to identify its structure.On the basis of hydroxyl radical assay,its antioxidant activity was investigated.The results showed that the purified fraction DMA was a single peak,and it mainly comprised of glucose.The repeating unit of DMA was →6)-α-D-Glc-p-(1→.DMA exhibited a scavenging activity for hydroxyl radical.

Key words: Dioscorea nipponica Makino, polysaccharide, antioxidant activity, NMR spectroscopy