Blumea riparia oligosaccharide (BROS) was obtained from branches of Blumea riparia by using ceramic and organic membrance separation, precipitation with ethanol, deproteination using Sevag method, and fractionation through DEAE-cellulose column, Sephadex G-10 and Sephadex G-50 Gel filtration chromatography. The purity and molecular weight of BROS were determined by HPGPC and MALDI-TOF-MS. The structure was characterized with monosaccharide composition analysis, methylation analysis, IR, GC-MS, 1D and 2D NMR analysis. The results showed that BROS was homogeneous oligo-saccharide and composed of one α-D-Glcp and seven β-D-Fruf. The molecular weight of BROS was 1314. The backbone of BROS had a consisting of 1,2-linked β-D-Fruf residues, α-D-Glcp-(1→ and β-D-Fruf-(2→ connecting each end of the molecular. Finally, the BROS structure was fixed on as: β-D-Fruf1-(2→1)-β- D-Fruf2-(2→1)-β-D-Fruf3-(2→1)-β-D-Fruf4-(2→1)-β-D-Fruf5-(2→1)-β-D-Fruf6-(2→1)-D-Fruf7-(2→1)-α-D-Glcp.

Key words: oligosaccharide (BROS), extraction and isolation, methylation reductive cleavage, NMR analysis, structure characterization