Ultrasonic-assisted aqueous two-phase extraction of polysaccharides from the fruits of Ilex cornuta (Lindl. Et Paxt.): Process optimization, structural characterization and antioxidant activity study

The aqueous two-phase extraction process (APTE) was utilized for the extraction of polysaccharides from the fruits of Ilex cornuta (Lindl. et Paxt.) (PFIC). After screening and selection of isopropanol/ammonium sulfate as the aqueous two-phase system, various parameters of crude extract amount, ultrasonic time, extraction temperature and extraction time on the extraction process was investigated in detail and optimized by response surface methodology (RSM). Under the optimal conditions in which crude extract amount was 2.23 g, ultrasonic time was 17.5 min, extraction temperature was 69 °C and extraction time was 1.55 h, the yield of polysaccharides reached 50.87% which was close to the predicted value of 50.78%. Structural features of PFIC were investigated by GPC, GC–MS and FT-IR analysis. And the results indicated that PFIC with a molecular weight of 3.89 kDa was composed of monosaccharides including rhamnose (1.83%), arabinose (11.70%), xylose (3.30%), mannose (3.55%), glucose (61.88%) and galactose (17.74%). The bioactivity experiments showed that PFIC had strong scavenging ability on DPPH radical, fine scavenging ability on hydroxyl radical and certain scavenging ability on superoxide anion radical. Overall, these results suggested that PFIC exhibiting fine to good antioxidant capacities could be potentially developed as a natural antioxidant.