Optimization of ultrasonic extraction of Flammulina velutipes polysaccharides and evaluation of its acetylcholinesterase inhibitory activity

Polysaccharide was testified to be the main component of Flammulina velutipes for inhibiting AChE activity in our preliminary study. Therefore, response surface methodology, based on Box-Behnken design, was used to optimize the ultrasonic extraction conditions of F. velutipes polysaccharides (FVP). Four independent variables (ratio of water to raw material, ultrasonic power, ultrasonic time, and ultrasonic temperature) were taken into consideration. A quadratic model, adequate for reasonably predicting the yield of FVP, was constructed between ultrasonic conditions and yield of FVP. A yield of FVP of 8.33% was obtained under a modified condition (ratio of water to material of 25 ml/g, ultrasonic power of 620 W, ultrasonic time of 20 min, and ultrasonic temperature of 45 °C). Subsequently, acetylcholinesterase (AChE) inhibitory activity and 1,1-diphenyl-2-picryl hydrazine (DPPH) scavenging activity of FVP were determined. AChE inhibitory rate of 18.51% and DPPH scavenging rate of 61.24% were obtained at 0.6 mg/ml of FVP, indicating a good potential of FVP to enhance learning and cognitive ability.