Optimization of Ultrasonic-Assisted Extraction of Polysaccharides from Polyporus umbellatus Sclerotium by Response Surface Methodology and Antioxidant Activity

To promote extraction efficiency of bioactive polysaccharides from sclerotium of Polyporus umbellatus, ultrasonic-assisted extraction was applied to extract polysaccharides from P. umbellatus sclerotium. The effects of extraction time, ultrasonic power, extraction temperature and liquid-to-material ratio on the yield of polysaccharide were investigated by combining single factor experiments and response surface optimization, and the optimal extraction parameters were also determined. Meanwhile, antioxidant activities were evaluated by DPPH free radical scavenging ability and reducing power test. The results showed that the yield of polysaccharides from sclerotia of P. umbellatus was significantly correlated to the interaction between extraction temperature and ultrasonic power, extraction temperature and liquid-to-material ratio, ultrasonic power and liquid-to-material ratio, liquid-to-material ratio and extraction time. The optimum extraction parameters were extraction temperature 72.0 ℃, extraction power 300 W, extraction time 65 min and liquid-solid ratio 22 mL/g, and the maximum yield was 2.47%±0.03%. PUPF30, PUPF60 and PUPF80 were obtained from polysaccharide extracts by graded ethanol precipitation. Their polysaccharide contents were respectively 39.99%, 58.60% and 50.35%, and the protein contents were respectively 25.80%, 14.42% and 25.54%. Within the tested dose range, PUPF30, PUPF60 and PUPF80 showed the highest DPPH scavenging rate of 50.63%, 83.95%, 87.48%, respectively, and the highest reduction power of 0.828, 1.433, 1.525, respectively. The ultrasonic-assisted extraction optimized by response surface methodology was preferable for effective extraction and preparation of bioactive polysaccharides from sclerotia of P. umbellatu. This study would lay a foundation for the further development and utilization of polysaccharides from sclerotia of P. umbellatus.