RESUMO
Objective: To investigate the influencing factors of sulfated modification of Bupleurum chinense polysaccharides (BCP),and to elucidate the possible mechanism of improving the antioxidant ability of sulfated BCP (S-BCP).Methods:BCP was sulfated by chlorosulfonic acid-pyridine method.The degree of substitution (DS)of S-BCP was observed by adjusting the volume ratios of chlorosulfonic acid to pyridine (1:2,1:4,and 1:8).The structures of BCP and S-BCP were analyzed by infrared (IR)spectroscopy,the morphology of BCP and S-BCP were observed under scanning electron microscopy (SEM).The antioxidant model was established by using 1, 1-diphenyl-2-picrylhydrazyl (DPPH)free radical scavenging.The experiment was divided into positive control group,BCP group and S-BCP group,and the scavenging rates of DPPH free radical in various groups were compared. Results:When the volume ratio of chlorosulfonic acid to pyridine was 1 : 4,the reaction time was 2 h and the reaction temperature was 60 ℃,the maximum sulfur content percentage of S-BCP was 18.62% and the DS was the highest (DS = 2.32 ).Compared with BCP group, the scavenging rate of DPPH free radical of S-BCP was significantly increased (P <0.05).Conclusion:The volume ratio of chlorosulfonic acid to pyridine can affect the DS of S-BCP.The sulfated modification can increase the anti-oxidant capacity of BCP by changing its physic-chemical characters and spatial conformation.