Antioxidant activity of maleoyl κ-carrageenans with different substituting degrees

Abstract:

Two κ-carrageenan oligosaccharides were prepared by acidic degradation. Then the maleyol derivatives (MA，MB) were synthesized with maleyol anhydride, respectively. The products were characterized by FTIR, the molecular weights (4 350, 4 540) were measured by gel permeation chromatography (GPC) method, and the substituting degrees (0.61, 0.44) were determined by colorimetry method. Their antioxidant activities were evaluated by the scavenging of superoxide anion, 1,1diphenyl2picrylhrazyl radicals (DPPH), H²O² and reducing power. The 50% inhibition concentrations (IC₅₀s) against superoxide anion of MA and MB were 0.441 and 0.489 mmol/L, respectively. As for DPPH radical scavenging, the IC₅₀s of MA and MB were 0.101 and 0.273 mmol/L, respectively. The IC₅₀against H²O² of MA was 0.052 mmol/L, MB failed to achieve halfinhibition in the test concentration. At a concentration of 0.5 mmol/L, and the absorbance of MA and MB was 0.894 and 0.487, respectively. The results indicated that MA showed better antioxidant activities than MB. The maleyol derivatives with higher substituting degrees have better antioxidant activity. It may be related to the nature of substituting group. In this paper, the relationship between the substituting degrees of the acylated κ-carrageenan oligosaccharides and their antioxidant activities was first reported. This research will be helpful to expand their applications in biomedicine.