Optimization of polysaccharides extraction from seeds of Pharbitis nil and its anti-oxidant activity

In the present study, polysaccharides were extracted from Pharbitis nil seeds (PNSs) by ultrasonic extraction method for the first time. Response surface methodology with Box–Behnken design was used to optimize the extraction process of PNS polysaccharides (PNSPs). Highest PNSPs yield 6.01 ± 0.15% that agreed closely with the predicted yield 5.99% were obtained under the optimal conditions as follows: ratio of water to raw material 6.5 mL/g, extraction temperature 49.0 °C, ultrasonic power 61.6 W, and extraction time 32.6 min. Preliminary characterization indicated that the sugar, uronic acid and protein contents of the product were 83.6 ± 1.61, 21.8 ± 1.25 and 16.4 ± 0.88% (w/w), respectively. FT-IR analysis revealed the general characteristic absorption peaks of polysaccharides. Besides, PNSPs showed a remarkable antioxidant activity in vitro in a dose-dependent manner. These may provide theoretical basis for further system research and rational development and utilization of PNS resources.