Optimization of extraction of crude polysaccharide from Cassia seed via ultrasonic assisted cellulase and study on its antioxidant activity

In order to improve the current low extraction rate of cassia polysaccharide and improve its extraction efficiency, the ultrasonic wave assisted cellulase extraction method of cassia polysaccharide is first proposed and optimized. Orthogonal test is conducted to analyze the influence of six factors related to cellulase and ultrasonic wave on the extraction of cassia polysaccharide, and at the same time to explore the antioxidant activity of the extracted polysaccharide in vitro. The results show that the main and secondary factors affecting the extraction rate of cassia polysaccharide are pH > ultrasonic power > enzyme dosage > enzymatic hydrolysis temperature > enzymatic hydrolysis time > ultrasonic time. The optimal conditions are: enzyme dosage: 1.6%, enzymatic hydrolysis time: 80 min, enzymatic hydrolysis temperature: 52 ℃, enzymatic hydrolysis pH: 6.4, ultrasonic time: 30 min, ultrasonic power: 276 W, the polysaccharide yield under the optimal conditions is 12.29%, which is 5.31% and 14.43% higher than the single enzyme extraction method and ultrasonic extraction method reported in the literature, respectively, indicating that the composite extraction method is superior to the single extraction method. The antioxidant activity analysis shows that the half inhibitory concentrations of cassia polysaccharide against DPPH·, ABTS·+, ·OH, ·O2- free radicals are 0.894 mg/mL, 1.175 mg/mL, 1.908 mg/mL and 7.601 mg/mL, respectively, which shows good antioxidant activity in vitro. Therefore, ultrasonic assisted cellulase extraction of crude polysaccharide from cassia seed is a new efficient and rapid extraction method.