Sulfated modification of the polysaccharides obtained from defatted rice bran and their antitumor activities

Nine sulfated defatted rice bran polysaccharides (sRBPS), with various degrees of sulfation (DS) and carbohydrate content, were prepared by chlorosulfonic acid–pyridine (CSA–Pyr) method according to orthogonal test. Nine sulfated derivatives sRBPS were obtained and their antitumor activities were compared by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The results showed that when DS within the scope of 0.81–1.29, carbohydrate content in the range of 41.41–78.56%, sulfated derivatives exhibit relatively strong antitumor activity in vitro. The optimum modification conditions were reaction temperature of 70 °C, the ratio of chlorosulfonic acid to pyridine of 1:4 and the reaction time of 2 h.