Preparation And In Vitro Activity Of Blueberry Polysaccharides

Blueberries are known as the "king of small berries" and are rich in nutrients,with physiological effects such as improving vision,antioxidant and strengthening immunity.At present,the most researched active ingredients of blueberry are anthocyanins,but the research on polysaccharides is relatively less,and more focused on the extraction process and the biological activity of crude polysaccharides.In this paper,blueberry polysaccharides by ultrasound-assisted hot water extraction,and the process parameters were optimized by response surface methodology.Then carries out deproteinization,decolorization,separation and purification of the crude polysaccharide,and then high performance liquid chromatography,Fourier infrared spectroscopy,scanning electron microscopy and other methods were used for structural identification.At the same time,carries out studies on the antioxidant,lipid-lowering and immune activities of blueberry polysaccharides in vitro.It is expected to provide reference for the application of blueberry polysaccharides in the field of food and medicine.The main results are as follows:(1)The factors influencing the extraction rate of blueberry polysaccharides were material-liquid ratio(X1),ultrasonic time(X3),ultrasonic power(X2)and ultrasonic temperature(X4),and the fitted regression equation between the extraction rate Y and each factor was:Y=-1.38425+0.055150X1+2.58250E003X2+0.063200X3+0.053667X4+8.75000E-006X1X2-2.50000E-004X1X3+5.00000E005X1X4-1.12500E-005X2X3+4.00000E-005X2X4-5.00000E-005X3X4-7.94167E004X12-3.76667E-006X22-5.44167E-004X32-7.81667E-004X42,The optimal parameters of the process were determined by optimization as 1:30 material to liquid ratio,580W ultrasonic power,49℃ ultrasonic temperature and 42min ultrasonic time,which resulted in a BFPs extraction rate of 2.90%.(2)The H2O2 method was the best decolorization method with 93.4%decolorization,and the polysaccharide retention was 79.1%.The papain+Sevag method was able to remove 72.94%of the protein and retain up to 81.5%of the polysaccharides.The three polysaccharide components BFP-1,BFP-2 and BFP-3 were separated by DEAE-52 column chromatography,and each group was identified as polysaccharides with uniform molecular weight by Sephadex G-100 dextran gel column.(3)The molecular weights of BFP-1,BFP-2 and BFP-3 were 5.547×104 Da,5.671 ×104 Da,3.951 ×104 Da,respectively.Using HPLC method,the main monosaccharides of BFP-1 and BFP-2 are glucose,galactose,xylose and arabinose,with molar ratios of 28.79:1.03:2.52:6.39 and 3.57:5.79:1.53:24.07,respectively,and the composition of BFP-3 monosaccharides is mainly galacturonic acid,glucose,galactose and arabinose,with a molar ratio of 4.61:1.96:3.27:3.7.Through SEM,it can be observed that the surface of the three components is rough,BFP-1 has a lamellar structure,and BFP-2 and BFP-3 have small and many pores,indicating that there is repulsion between molecules.FT-IR showed that blueberry polysaccharides were αtype glycosidic bond-linked pyran polysaccharides,and Congo red tests showed that BFP-1 had a typical triple helix structure.(4)The four polysaccharides showed better scavenging of DPPH and·OH radicals,but low scavenging ability for ABTS+radicals,with the scavenging rate of BFP>BFP-3>BFP-1>BFP-2 in descending order.In terms of binding capacity to cholate,the binding capacity of polysaccharides to sodium glycocholate is greater than that of sodium taurocholate,but they are all proportional to the concentration,and the binding rate is BFP-3>BFP-1>BFP-2>BFP at the same concentration.The results of in vitro immunization showed that macrophages RAW 267.4 treated with polysaccharide has a significant increase in NO production in the concentration range of 125-1000μg/mL compared to the control group,and the order of immune ability was BFP-3>BFP-1>BFP-2.It is concluded that the in vitro activity of different polysaccharide components is different,and BFP-3 has better in vitro oxidation,hypolipidemia and immune enhancement.