Extraction, purification, characterization and antioxidant activity of polysaccharides from Piteguo fruit

• Polysaccharides were extracted from Piteguo which grow at a high altitude of 2100–2400 m in Hezheng County, Gansu Province, China.
• Polysaccharides from Piteguo were studied for the first time, and response surface methodology was applied to predict optimum conditions for extraction of polysaccharides.
• Antioxidant activities and preliminary structural characterization of the polysaccharides was studied.

Piteguo fruit (PTG) picked from the trees growing at a high altitude of 2100–2400 m in Gansu Province, China, is rich in a variety of nutrients, especially the polysaccharide. The optimum conditions for ultrasonic-assisted extraction Piteguo polysaccharide (PTGP) were investigated by response surface methodology (RSM), including ratio of water to raw material, extraction time, extraction temperature and ultrasonic power. The result was shown as follow, ratio of water to raw material at 13:1 mL/g, extraction time of 66 min, extraction temperature at 70 °C, ultrasonic power at 230 W, and the yield was 5.16% ± 1.81%. While the predicted yield of PTGP was 5.25% under the optimum conditions. Two homogenous polysaccharide (PTGP1 and PTGP2) were obtained by DEAE-cellulose-52 and Sephadex G-100 column chromatography. PTGP1 and PTGP2 were confirmed to be composed with three and two different kinds of polymers by HPSEC-LLS, respectively. The monosaccharide composition detected by GC–MS indicated that PTGP1 was a heteropolysaccharide consisting of rhamnose, arabinose, xylose, mannose, glucose and galactose with the molar ratio of 3.06:2.32:1.56:4.87:3.28:2.18, however mannose has not been detected in PTGP2. Evaluation of the antioxidant activity in vitro suggested that PTGP1 and PTGP2 had significant scavenging activity of hydroxyl, superoxide anion and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. Overall, the polysaccharides from Piteguo Fruit may have potential applications in the medical and food industries.