Extraction optimization, isolation, preliminary structural characterization and antioxidant activities of the cell wall polysaccharides in the petioles and pedicels of Chinese herbal medicine Qian (Euryale ferox Salisb.)

Cell wall polysaccharides in the petioles and pedicels of Qian (Euryale ferox Salisb.) (EFPP) were extracted using ultrasound-assisted technique. Response surface methodology (RSM) based on Box–Behnken design (BBD) was employed to optimize extraction parameters for the maximum purity of polysaccharides. The results showed that the optimum extraction conditions were extraction temperature of 80 °C, extraction time of 32 min, ultrasonic power of 270 W and liquid-to-solid ratio of 40 mL/g. Under the optimal conditions, the experimental purity of polysaccharides was 62.57% ± 1.68%, which was very close to the predicted. The crude EFPP were isolated using DEAE-52 column and four major fractions (EFPP-1, EFPP-2, EFPP-3 and EFPP-4) were obtained. Typical functional groups of polysaccharides were characteristic for EFPP-1, EFPP-3 and EFPP-4 from FT-IR spectrum. Furthermore, the crude EFPP and three fractions (EFPP-1, EFPP-3 and EFPP-4) possessed appreciable in vitro antioxidant effects on α,α-diphenyl-β-picrylhydrazyl (DPPH), 2,2′-azinobis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), hydroxyl radical scavenging and reducing powers. Then, the crude EFPP and EFPP-4 could effective against H2O2-induced injury on HUVEC and VSMC through enhancement of T-AOC, SOD and CAT activities and decrease of MDA content.