Optimization for Sulfation Techniques of Dictamnus Dasycarpus Polysaccharide by Central Composite Design-response Surface Method and Study on Its Antioxidant Activity

OBJECTIVE To optimize the sulfated process of Dictamnus dasycarpus polysaccharides(DDP) by central composite design-response surface methodology, compared with the polysaccharide structural feature without chemical modification and investigate its antioxidant activity. METHODS Chlorosulfonic acid-pyridine method processing technology was optimized by esterification reagent proportion, esterification reagent with polysaccharide solution proportion, reaction temperature, reaction time as independent variables and the degree of substitution as dependent variable, each level of independent variables were fitted by multiple regression fitting. Response surface methodology was used to select optimum processing technology; sulfated polysaccharides from Dictamnus dasycarpus(SDDP) were obtained after identified through IR and SEM. Antioxidant activity of SDDP was researched by setting the different concentration of the sample solution and adopting the free radical-scavenging(DPPH, OH·, O₂^-·) capacity of DDP and SDDP as the indicators. RESULTS The optimums were as follows:the esterification reagent proportion was 1:4, esterification reagent with polysaccharide solution proportion was 1:1, reaction temperature was 73℃, and reaction time was 5 h. The IR spectra exhibited that the characteristic peaks of sulfate at near 820 cm^-1 and 1 254 cm^-1 of SDDP. The results of IR revealed that DDP was modified successfully after sulfation. The SEM exhibited the surface of SDDP was roughly arranged and the bulk volume was obviously less than DDP. It was discovered that DDP and SDDP both had the strong free radical scavenging ability for DPPH, OH· and O₂^-·. Compared with the polysaccharides without chemical modification, the reducing power of SDDP was stronger. CONCLUSION This optimized processing technology of SDDP is simple and feasible with good predictability. After sulfation, the antioxidant activities of DDP have been improved.