The Optimized Ultrasonic Extraction of the Polysaccharide from <em>Pleurotus eryngii</em> by Response Surface Methodology and Assessing Its Antioxidant Activity

We aimed to investigate the effects of ultrasonic treatment on the yield of polysaccharide in the extraction and antioxidant activity of polysaccharide. By employing an ultrasonic technique, polysaccharide was extracted from Pleurotus eryngii (PPE). The optimal conditions for ultrasonic extraction of PPE were revealed utilizing Response Surface Methodology (RSM) which was adopted to assess the effects of four variables on the extraction of PPE. These variables included temperature, time, ultrasonic power and solvent-solid ratio and were independent to each other. The plots of response surface showed that these variables presented complicated and significant effects on the extraction of polysaccharide. To obtain the highest recovery of polysaccharide, ultrasonic extraction was performed at 95°C for 82 min with a solvent-solid ratio of 20 mL/g and an ultrasonic power of 213 W. The estimated recovery was 14.5%. The determination of extractions in the experiments under optimal conditions showed insignificant differences with the estimated recovery. Following these experiments, the antioxidant activity in vitro was assessed by detecting scavenging ability against DPPH, superoxide anions and hydroxyl radicals. A 45.6% removal rate for DPPH was observed at 2.5 mg/ml of PPE.