Abstract: Objective: To isolate and purify a polysaccharide from dried roots of Polygala tenuifolia and to determine its physicochemical properties and biological activity. Methods: The purified polysaccharide was obtained by ultrasonicassisted extraction, alcohol fractional precipitation, deproteinization, decolorization, dialysis, DEAE-cellulose 52 and Sephadex G-100 gel column chromatography. The purity of the final purified product was determined by UV-visible spectroscopy, spin spectrophotometry and gel filtration chromatography (GPC). The relative molecular mass of the polysaccharide was determined by high performance gel permeation chromatography, the monosaccharide composition was analyzed by high performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD), the antioxidant activity was evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl free radical scavenging assays, and the hypoglycemic activity was evaluated by α-glucosidase-inhibiting activity. Results: A homogeneous polysaccharide (PTP-1) was obtained. The relative molecular mass of PTP-1 was 4.62 × 104. Its monosaccharide composition was composed of galactose, glucose and mannose with a molar ratio of 3.92:1.00:2.08. The polysaccharide showed DPPH and hydroxyl radical scavenging capacity in a dose-dependent manner in a certain concentration range, with IC50 of 0.35 and 0.51 mg/mL, respectively. In addition, it was able to significantly inhibit α-glucosidase activity with IC50 of 0.52 mg/mL. Conclusion: PTP-1 is a pure polysaccharide with antioxidant and hypoglycemic activity.

Key words: Polygala tenuifolia, polysaccharide, physicochemical property, antioxidant activity, hypoglycemic activity