Ultrasonic-assisted enzymatic extraction of Sparassis crispa polysaccharides possessing protective ability against H2O2-induced oxidative damage in mouse hippocampal HT22 cells

Sparassis crispa polysaccharides have recently attracted considerable attention due to their excellent bioactivities. However, their extraction procedure is often tedious, time-consuming, and environmentally unfriendly; it even causes damage to their structures and reduces their bioactivities, all of which hinder their further development to some extent. Therefore, the ultrasonic-assisted enzymatic extraction (UAEE) technology was optimized to extract polysaccharides from Sparassis crispa (SCP) by the response surface methodology. The yields, physicochemical properties, and antioxidant activities of SCPs obtained from UAEE and conventional hot water extraction (HWE) were evaluated. According to the optimal parameters, the yield of SCPs extracted by UAEE reached up to 14.63%, which increased by 68.54% compared with that obtained from the conventional hot water extraction (HWE) method. Additionally, the UAEE methods affected the contents of the polysaccharides, molecular weights, and the molar percentage of the constituent monosaccharides of SCPs. SEM analysis indicated that the microstructures of the two SCPs were notably different. Antioxidant assays showed that both SCPs possessed good antioxidant activities against DPPH, ABTS˙+, and hydroxyl radicals in vitro. Additionally, the SCPs extracted by UAEE attenuated the HT22 cell neurotoxicity induced by H2O2 by the means of ameliorating cell viability, reducing extracellular LDH release, and decreasing the levels of intracellular ROS. These results provide scientific basis for the further investigation of SCPs as potential neuroprotective agents.