Study On Synthesis, Characterization And Bioactivities Of O-succinyl Derivatives Of Low-molecular-weight κ-carrageenan

Low-molecular-weight κ-carrageenan (LMW-KC) with the number-average molecular weight of 10060 was achieved by degrading κ-carrageenan (KC) with hydrochloric acid, and then was turned into tetrabutylammonium salts. The salts were dissolved in N, N-dimethylformamide (DMF) and acylated by succinic anhydride at the temperature of 60℃ and 80℃ respectively in the presence of dimethylaminopyridine (DMAP) and tributylamine as catalysts, resulted in O-succinyl derivatives of LMW-KC. Characterization of the title compounds were performed by IR, GPC, 13C NMR, 1H NMR, 1H/1H COSY, 13C/1H HMQC, HMBC and TGA. The antioxidant activities and the antibacterial activities of LMW-KC and its derivatives were studied. The results were showed as follows:Low-molecular-weight κ-carrageenan (LMW-KC) with the number-average molecular weight of 10060 and weight-average molecular weight of 15350 was achieved by degrading κ-carrageenan (KC) with 0.1 mol/L hydrochloric acid for 1h. Compared with κ-carrageenan, the disaccharide repeating units of LMW-KC were not destroyed, and the content of S was not changed.O-succinyl derivatives of low-molecular-weight κ-carrageenan were synthesized at 60 ℃ and 80 ℃ for 6 h, succinoylate substitution of which were 2.60 and 2.92, respectively. Mono-ester derivativies with succinyl group were formed, and the structure of disaccharide repeating units were not destroyed after acylation. Hydroxyl groups at C2 of βGalp4 residues of κ-carrageenan were completely substituted, while those at C6 of βGalp4 residues and C2 of αAnhy residues were partly substituted. The thermal stability of the derivatives was increased apparently.The activities of acylated derivatives for scavenging hydroxyl radical, H₂O₂ and superoxide radial anion were obviously increased. The performance of O-succinyl derivatives at 60℃ for 6h were superior to other derivatives; O-succinyl derivatives scavenging rate for hydroxyl radical and H₂O₂ was as high as 92.35% and 97.14% at 60℃ for 6h, respectively, while activities for superoxide radial anion were nearly two times as high as LMW-KC at the same concentration.