Physicochemical features and antioxidant activity of polysaccharides from Herba Patriniae by gradient ethanol precipitation

Four polysaccharides BJP50, BJP60, BJP70 and BJP80 (total named BJPs) were separated from Herba Patriniae via gradient ethanol precipitation with 50%, 60%, 70% and 80%, respectively. After decolorization and deproteinization, their physicochemical features and antioxidant activities were investigated. The results showed that the total sugar content of BJPs accounted above 50% but no protein contained, while BJP50 and BJP60 contained a small amount of uronic acid. GC analysis indicated that BJPs were mainly composed of galactose, arabinose, glucose, mannose, xylose and rhamnose. From BJP50 to BJP80, the types of monosaccharides and the content of arabinose, glucose and mannose increased but that of galactose and rhamnose decreased, and their molecular weights gradually reduced from 2.3 × 10⁶ to 4.5 × 10³. BJPs had a good thermal stability with the order of BJP80 > BJP70 > BJP60 > BJP50. The vitro bioactivity assay showed that BJP80 and BJP70 exhibited stronger scavenging capacities for DPPH, ABTS and hydroxyl free radicals than that of BJP60 and BJP50. As the concentration reached 4 mg/mL, the scavenging capacities of BJP80 and BJP70 on DPPH and hydroxyl free radical were up to 92% and 95%, respectively, and their antioxidant activities gradually approached to the positive control.