Abstract:

【Objective】Optimize the extraction process of mistletoe polysaccharide and investigate its antioxidant activities，to provide references for the extraction and utilization of mistletoe polysaccharide.【Methods】Using polysaccharide yield as the evaluation index and single factor experiment method to analyse the effect of solid-liquid ratio，ultrasonic time，ultrasonic temperature and ultrasonic power on the polysaccharide yield of mistletoe. The response surface methodology was adopted to optimize the extraction process of mistletoe polysaccharide. Additionally the scavenging abilities of mistletoe polysaccharide on DPPH free radicals，and ABTS free radicals as well as the total reducing power of trivalent iron ions were tested.【Results】Under different factor levels，the solid-liquid ratio of 1∶30（g∶mL），ultrasonic temperature of 70 ℃，ultrasonic time of 20 min，and ultrasonic power of 300 W had the highest yield of mistletoe polysaccharide at 3.85%，5.59%，8.60%，and 5.86%，respectively. The effects on the yield of mistletoe polysaccharide were as follows：ultrasonic temperature>ultrasonic time>ultrasonic power>solid-liquid ratio. After optimized with response surface methodology the highest yield of mistletoe polysaccharide of 8.17% was obtained with solid-liquid ratio of 1∶29（g∶mL），ultrasonic time of 15 min，ultrasonic temperature of 64 ℃，and ultrasonic power of 300 W. The scavenging abilities of 2 mg/mL polysaccharide solution on DPPH and ABTS free radicals were 79.07% and 51.38%，with IC₅₀ 0.612 and 2.611 mg/mL，respectively. The total reducing power of trivalent iron ions was 0.33.【Conclusion】The optimal conditions for the extraction of mistletoe polysaccharides were：solid-liquid ratio of 1∶29（g∶mL），ultrasonic time of 15 min，ultrasonic temperature of 64 ℃，ultrasonic power of 300 W. Mistletoe polysaccharides had scavenging effects on DPPH free radicals，ABTS free radicals and reducing effects on trivalent iron ions.

Key words: Mistletoe, Polysaccharide, Process optimization, Response surface methodology, Antioxidant activity