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To investigate the effect of sulfated modification on the structure and function of coconut haustorium polysaccharide (CHP), three kinds of sulfated coconut haustorium polysaccharides (SCHP-2, SCHP-3, and SCHP-4) were prepared using sulfation reagents containing different ratios of chlorosulfonic acid and pyridine (v/v, mL/mL: 1/2, 1/3, and 1/4) after extracting CHP from the raw materials of coconut haustorium, and their basic chemical compositions, structural characteristics and antioxidant activity in vitro were compared and analyzed. Results showed that all three sulfation reagents were able to modify CHP (characteristic peaks of S=O and C-O-S were observed near 1100~1250 cm−1 and 820 cm−1 in infrared spectra, respectively), and the degree of substitution (DS) was the highest (0.75) at the ratio of chlorosulfonic acid and pyridine for 1/2. The total sugar, uronic acid content, and molecular weight of the three SCHP decreased, and the molar content of monosaccharides also changed when comparing with that of CHP. The thermal stability had slightly weakened as well (the degradation temperature of polysaccharides decreased from 211.17 ℃ and 282.01 ℃ of CHP to 194.86~207.70 ℃ and 233.35~262.46 ℃ of SCHP, respectively). The results of antioxidant experiments in vitro showed that the scavenging activity of SCHP on DPPH and hydroxyl radicals was lower than that of CHP, and the larger the DS was, the more obvious the decrease in activity was. In terms of the ABTS+ radicals scavenging ability and ferrous ions chelating activity, increasing DS could enhance the activity of SCHP. At 8 mg/mL, the ABTS+ radicals scavenging rate (54.82%) and ferrous ions chelating rate (15.59%) of SCHP-2 were significantly (P

To investigate the effect of carboxymethylated with different degrees of substitution on the properties of Siraitia grosvenorii polysaccharide (SGP), carboxymethylated Siraitia grosvenorii polysaccharide (CSGP) was prepared by solvent method by using the raw material of SGP. The effects of chloroacetic acid concentration, reaction time, and sodium hydroxide concentration on the degree of substitution were analyzed, and the CSGP with the degree of substitution ranging from 0.28 to 1.09 was prepared. The physicochemical properties of CSGP with different substitution degrees were characterized, and the effects of substitution degrees on hypoglycemic activity and antioxidant activity were investigated by in vitro physiological activity experiments. The high-performance gel permeation chromatography revealed that the molecular mass of CSGP was smaller than that of SGP. The results of FTIR manifested a new absorption peak at 1317 cm−1, indicating that carboxymethyl was successfully introduced into the polysaccharide. The results of scanning electron microscopy showed that with the increase of substitution degree, the surface morphology of CSGP became more fragmented and appeared to curl. Congo red experiment revealed that the triple helix structure of CSGP with high substitution degree disappeared. In vitro physiological activity experiment showed that 6 mg/mL of the CSGP-M had the highest α-amylase inhibition, DPPH, and hydroxyl radical scavenging rates of 44.36%±1.30%, 63.17%±2.07%, and 70.21%±1.89%, respectively. Compared with SGP, CSGP-L and CSGP-H, CSGP-M with medium degree of substitution has the best hypoglycemic activity and antioxidant activity in vitro. When the degree of substitution was increased to 1.09, the inhibition rate of α-amylase, DPPH and hydroxyl radical scavenging rate of CSGP-H decreased to 11.65%±0.26%, 47.45%±0.79%, and 34.85%±0.78%, respectively. The results indicated that CSGP with medium degree of substitution could exert the best physiological activity.