Abstract: Seven carboxymethylated derivatives of polysaccharide from Zizyphus jujuba fruits (ZJP) were prepared by the reaction between ZJP and monochloroacetic acid. The degree of substitution (DS), solubility, molecular weight, and biological activity of each derivative were determined. Results showed that the DS of each derivative was 0.016－0.220. pH values higher than 12 were good for the substitution of carboxymethyl groups, but the yield of carboxymethylated products decreased sharply due to higher pH. The molecular weight of carboxymethyl ZJP (CM-ZJP) was reduced gradually with increasing NaOH amount during the carboxymethylation reaction. The infrared spectrum of CM-ZJP revealed that ZJP was successfully carboxymethylated without the change of ZJP structure during carboxymethylation. The carboxymethylation of ZJP exhibited an enhanced inhibitory effect againstα-glucosidase and a declined inhibitory effect againstα-amylase. Moreover, carboxymethyl substitution of ZJP at lower substitution degree (DS = 0.016－0.082) could decrease the inhibitory effect against hyaluronidase activity and increase the inhibitory effect against hyaluronidase activity at higher substitution degree (DS = 0.200－0.220).

Key words: carboxymethyl Zizyphus jujuba polysaccharide, activity, α-amylase, α-glucosidase, hyaluronidase