[Comparison on biological activities of Lycium barbarum polysaccharides extracted with five methods].

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.

[Effects of different extraction methods on chemical compositions and biological activities of polysaccharides from Lycium barbarum].

In this study, five polysaccharides from Lycium barbarum(LBPs)(LBP-1-LBP-5) were selectively extracted by different extraction methods, and the chemical composition, structural characteristics, and biological activities of LBPs were explored. The results of chemical composition analysis showed that alkaloids were not detected in the five LBPs. The total polysaccharide content was(81.95%±1.6%)-(92.96%±0.76%), the uronic acid content was(8.26%±0.46%)-(24.81%±0.46%), and the protein content was(0.06%±0.03%)-(1.35%±0.13%). The monosaccharide compositions of the five LBPs were basically same, mainly including glucose, xylose, and galactose. However, there was significant difference in the content ratio of different monosaccharide. The results of infrared spectra analysis indicated that the five LBPs had typical infrared spectral characteristics of polysaccharides. The results of nuclear magnetic resonance characteristic spectrum analysis revealed that the five LBPs had two configurations of α and ß. Meanwhile, there were triple helix structures in LBP-2, LBP-3, and LBP-4, which enhanced the activities of polysaccharides. The results of activities screening suggested that the biological activities of the five LBPs were significantly different. LBP-3 showed the highest lipid oxidation clearance rate, and its antioxidant activity was equivalent to that of the positive control group. The inhibitory rate of LBP-4 on α-amylase and its activation rate of alcohol dehydrogenase were better than those of other fractions, and the inhibitory rate of LBP-4 on α-amylase was slightly higher than that of the positive control group when the mass concentration was 10 g·L~(-1). LBP-2 showed stronger inhibitory activity against α-glucosidase and hyaluronidase. This study provides references for the precise development and utilization of LBPs.