Extraction optimization and characterization of polysaccharide antioxidants from Pinellia ternata   (Thunb) Breit rhizome

Purpose: To investigate the optimum extraction conditions of polysaccharides from Pinellia Rhizoma (PRP) and their antioxidant activities.
Methods: Response surface methodology (RSM) was applied to optimize the water extraction conditions of PRP by Box-Benhnken design (BBD). A high performance liquid chromatography (HPLC) method was performed for determining the monosaccharide composition, while a high performance gel permeation chromatography (HPGPC) method was established for determining the molecular weight distribution of PRP. In addition, scavenging DPPH and superoxide anion radical scavenging assays were used to evaluate the antioxidant activities of PRP.
Results: As a result, the optimum extraction conditions of PRP were as follows: extraction time, 103 min; solid-liquid ratio, 24 g/mL; and extraction no., 3. Under these conditions, the maximum extraction yield of PRP was 2.47 %, which matched the optimum value (2.55 %) predicted by RSM. The results of HPLC analysis suggest that the monosaccharide composition of PRP was mannose (Man), galactose acid (Gal acid), galactose (Gal), glucose (Glc), and arabinose (Ara) in molar ratios of 5.76:2.20:2.64:4.57:1, respectively, and the molecular weight ranged from 13592 to 445065. Furthermore, PRP showed marked antioxidant activities with the highest DPPH free radical scavenging rate of 71.5 % and O^2- free radical scavenging rate of 87.5 % at a concentration of 10 mg/mL.
Conclusion: RSM is a rapid and effective statistical technique for optimizing conditions for PRP extraction. Furthermore, PRP is a potential natural source of antioxidants.

Keywords
Pinellia rhizoma; Polysaccharides Optimization extraction; Monosaccharide composition; Antioxidant activity