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In recent years, it was found that the carbohydrates have many bioactivities, including improvement of immunity, antitumor, radioresistance and antiviral. Carbohydrates was expected to become the important drug which could overcome disease. In the fields of strengthening the development of saccharides drug, seeking high-efficiency carbohydrate drugs, and modifying structure of the known sugar to enhance its biological activity, these fields had been hot topics at home and abroad. Burdock oligosaccharide was a fructooligosaccharide separated from medicinal plants, with 13 of the polymerization degree. Burdock oligosaccharide had some bioactivities on the growth-promoting of bifidobacterium., antitumor and the improvement of immunity, and it was also studied as food and forage additive or natural medicine.In this paper, crude sample of burdock oligosaccharide was separated from fresh burdock root with 20.58% of yield. Through purification, we got pure sample with 85.13% of yield and oligosaccharide content is 98%. The structure of Burdock oligosaccharide was determined using high gel permeation chromatography (HPLC), the infrared absorption spectrum (IR), and nuclear magnetic resonance detection (NMR).In this study, The structure of Burdock oligosaccharide was modified with acetyl and sulfate groups, and determined by methods of IR and NMR. With acetic anhydride as acetylize reagent, glacial acetic acid as reaction solvent and sodium hydroxide with a concentration of 50% as catalyst, Burdock oligosaccharide acetate were obtained by changing the material ratio and other reaction conditions, and the degree of substitution (DS) are 0.53, 0.72, 0.94, 1.47, and rate of production were 47.2%, 54.7%, 58.4%, 65.8%, respectively. The sulfated modification was processed by methods of sulphur trioxide-pyridine and chlorosulfonic acid-pyridine, and then the effects of DS of Burdock oligosaccharide acetate were discussed under different reaction solvent, rat of charge, reaction temperature and reation time. By comparative analysis we identified the optimum reaction condition was: sulfation reagent was sulphur trioxide-pyridine, reaction reagent was dimethylformamide, fundamental reaction temperature was 40℃, the optimum reaction time was 2 h. Under the optimum reaction conditions, Burdock oligosaccharide sulfate was successfully prepared with DS of 0.42, 0.73, 1.25, 1.45. In the aspect of biological activity, effects of Burdock oligosaccharide derivatives with different DS and substituent on enhancing the growth of bifidobacterinu and regulating organism immunocompetence were studied. We found that oligosaccharide derivatives with DS﹤1 could obviously boost growth of bifidobacterinu and to be optimum at 1.0 mg/mL, while effects of DS﹥1 unconspicuously. In the study of the proliferation of immunocyte, all Burdock oligosaccharide derivatives could promote ability of swallow neutral red of intra-abdominal macrophage, and Burdock oligosaccharide acetate with DS of 0.72, 0.94 and sulfate with DS of 0.42,0.73 had more effects obviously, reaching maximum at concentration of 250μg/mL; Burdock oligosaccharide acetate with DS of 0.73 and sulfate with DS of 0.42, 0.73 could enhance lymphocytic proliferation prominently, the former reaching maximum at concentration of 250μg/mL and the latter at concentration of 100μg/mL can reached the best effects, while other derivatives was not evident.
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