Ultrasound-assisted enzymatic extraction of polysaccharides from Paulownia flowers : process optimization, structural characterization, antioxidant and hypoglycemic activities

This study aimed to optimize the ultrasound-assisted enzymatic extraction (UAEE) process of Paulownia flowers polysaccharides (PFP) and investigate its antioxidant and hypoglycemic activities. The optimal extraction conditions were cellulase dosage 1.6 mg/g, liquid-solid ratio 27:1mL/g, ultrasonic power 230 W, temperature 51 °C, the PFP yield reached 5.50 % which was close to the predicted value of 5.59 %. Furthermore, the PFP was isolated and purified by DEAE-52 cellulose column and sephadex G-200 column to obtain two polysaccharide fractions, PFP1-1 and PFP2-1. The characteristics, antioxidant activity and hypoglycemic activity of PFP1-1 and PFP2-1 were analyzed. PFP1-1 with a molecular weight of 52.8 kDa was mainly composed of mannose and glucose (molar ratio1.00:5.05), and PFP2-1 with a molecular weight of 8.768 kDa was consisted of mannose, rhamnose, glucuronic acid, glucose (molar ratio 1.00:7.41:8.09:11.30). Compared to PFP1-1, the antioxidant activity assays showed that PFP2-1 exhibited stronger DPPH radical, hydroxyl radical and superoxide radical scavenging capacity and the inhibitory activities revealed that PFP2-1 could more effectively inhibit α-amylase and α-glucosidase, which might be attributed to the uronic acid and low molecular weight in PFP2-1. This work will provide a foundation for the efficient extraction of PFP and utilization for antioxidant agent and digestive enzymes inhibitor of diabetes.