Abstract: Two low-molecular-weight (LMW) κ-carrageenans (A,B) were prepared by oxidative degradation of κ-carrageenan polysaccharides (KC).The LMW κ-carrageenans were then reacted with maleic anhydride to obtain two maleoyl LMW κ-carrageenans (MA,MB).Molecular weights and structural changes of A,B,MA and MB were determined.Their antioxidant activities were evaluated by superoxide anion radical (O₂^-·) scavenging assay,1,1-diphenyl-2-picrylhydrazyl radical (DPPH.) scavenging assay and total reducing power assay.The order of the antioxidant activities of the 4 investigated compounds was as follows:MA > A,MB > B;B > A,MB > MA.The results indicated that the chemical modification of LMW κ-carrageenans can enhance their antioxidant activity,and the antioxidant activity of LMW κ-carrageenans and their maleoyl derivatives increased with the increasing of molecular weights.These results were possibly related to the number of hydroxyl groups and the property of substituting groups.

Key words: Low-molecular-weight &kappa, -carrageenan, maleoyl, antioxidant activity