Abstract:Gracilaria lemaneiformis was used as the raw material to compare the properties of four polysaccharide extraction processes: GWP, GUP, GUWP, and GCP, which involve extractions using hot water, ultrasonic waves, ultrasonic-hot water, and citric acid, respectively. The results showed that GCP had the highest yield of 17.81 ± 0.34% among the four polysaccharides, relatively low molecular weight and apparent viscosity, and a high degree of uniformity of molecular weight. Antioxidant activity analyses indicated that GCP exhibited a relatively strong antioxidant capacity, and the oxygen radical absorbance capacity (ORAC) value was 298.735 ± 6.57 μmol Trolox/g. When the concentration of GCP was 2.0 mg/mL, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity and the reducing power were 65.79 ± 0.3% and 0.765 ± 0.01, respectively, which were significantly higher than the values of polysaccharides extracted using other methods. In addition, GCP could effectively inhibit α-amylase activity. Correlation analysis showed that the antioxidant activity and inhibitory effect on α-amylase of the polysaccharides from Gracilaria lemaneiformis had a positive correlation with the content of polysaccharides and uronic acid, and a negative correlation with the sulfate group content, molecular weight, polydispersity index (PDI) value, and viscosity. Therefore, citric acid extraction is an effective method to extract polysaccharides from G. lemaneiformis. This method can effectively increase the polysaccharide yield and the uronic acid content in the product, reduce the sulfate group content, molecular weight, and viscosity, and improve the molecular weight uniformity of polysaccharides.
