Studying the physicochemical properties and biological activities of Lycium barbarum polysaccharides(LBPs) is of great significance. The previous study had extracted LBPs(LBP-1, LBP-2, LBP-3, LBP-4, and LBP-5) by five different methods(cold water extraction, boiling water reflux extraction of the residue after cold water extraction, ultrasonic extraction with 50% ethanol, ultrasonic extraction with 25% ethanol of the residue after 50% ethanol extraction, and hot water extraction). In this study, the structures of the obtained five LBPs were characterized by UV spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Furthermore, the antioxidant, blood lipid-lowering, nitrosation-inhibting, acetylcholinesterase-inhibiting, and tyrosinase-inhibiting activities of the five LBPs were measured in vitro. The results showed that high-temperature extraction destroyed the polysaccharide structure, while ultrasound-assisted extraction ensured the structural integrity. The thermal stability and degradation behaviors differed among the five LBPs. However, the UV spectroscopic results of the five LBPs did not show significant differences, and all of the five LBPs showed the characteristic absorption peaks of proteins. LBP-3 and LBP-4 exhibited strong antioxidant activity, while LBP-3 had the strongest blood lipid-lowering activity. In addition, LBP-3 outperformed other LBPs in inhibiting nitrosation and acetylcholineste-rase, and LBP-2 showed the strongest inhibitory effect on tyrosinase. This study explored the effects of different extraction methods on the physicochemical properties and biological activities of LBPs, with a view to providing a basis for the selection of suitable extraction methods to obtain LBPs with ideal biological activities.
Keywords: Lycium barbarum polysaccharides; biological activity; comparative study; structure.