Abstract: In order to optimize the sulfated modification conditions of polysaccharides from Allium macrosttemon Bge. (PAM) and to investigate the probability of enhancing antioxidant activity of PAM after sulfated modification,total PAM was extracted by ethanol precipitation and three fractional PAMs obtained by chromatography were modified by chlorosulfonic acid-pyridine method.The modification conditions were optimized by response surface analysis with the ratio of chlorosulfonic acid to pyridine,reaction temperature and time as the factors.The degree of substitution (DS) was tested by sulfate barium turbidimetric method.The in vitro antioxidant activity of modified product was measured by H₂O₂/Fe²⁺ and pyrogallol systems.The result showed the optimal conditions were as follows:chlorosulfonic acid to pyridine of 1:3,reaction temperature of 65 ℃ and reaction time of 2 h.Under these conditions,the sulfate substitution degree of 0.470 was obtained.In addition,the in vitro antioxidant assays showed that the antioxidant activity of PAM was enhanced by sulfated modification.

Key words: Allium macrosttemon Bge.polysaccharides, sulfated modification, response surface methodology, antioxidant activity