Study On Structure And Bioactivity Of Water Soluble Polysaccharides Extracted From Litchi Chinensis Sonn Using Ultra-high Pressure Technology

Litchi(Litchi chinensis Sonn.)is a kind of fruit widely grown in tropical and subtropical areas,it cntains a large amount of sugar,as well as vitamins,proteins and organic acids,which is considered to be beneficial to human health.In this study,ultra-high pressure technology was used to extrat water-soluble litchi polysaccharides extracted from litchi fruit pulp under normal temperature conditions.In addition,polysaccharide isolation,purification,structure and antioxidation was studied.The main results are as follows:Polysaccharides yield was the respose value,the extraction process of water soluble litchi polysaccharides was studied.Based on the studies of single factors,the response surface analysis was used to optimize the conditions of ultra-high pressure extraction of water-soluble litchi polysaccharide,the optimization conditions are as follows: time 17.19 min,liquid-solid ratio 15,the pressure 463.9 MPa.The validation test showed that the highest yield was 12.01±0.23%,which was consistent with the theoretical prediction.The regression model also has well accuracy and feasibility.Polysaccharides from litchi pulp were extracted by four processing techniques: hot water,ultra-high pressure,ultrasonic and microwave(denoted as LPH,LPP,LPS and LPM).Ultra-high pressure extraction have the highest yield(12.01%)and the content of polysaccharides(79.72%).The physical and chemical properties analysis showed that four kinds of litchi polysaccharide contains no starch,reducing sugar or polyphenols.Four kinds of litchi polysaccharide has the similar structure,LPP and LPH contain uronic acid;LPS,LPH and LPP have ?-dominating configuration in pyranose form sugars.LPH has the highest average molecular weight(320213),Mw/Mn is 3.41.The surface structure of four kinds of litchi polysaccharide were different from each other.LPH,LPP and LPM composed of rhamnose,fucose,mannose,galactose and glucose,the LPS is different.In vitro antioxidant activity of four polysaccharides was evaluated by reducing power,scavenging activity against DPPH and OH radicals with the following trend: LPP>LPH>LPM>LPS.In the purification process,LPP was eluted through DEAE-52 and Sephadex G-100 cellulose gel column,LPP1 a and LPP2 were obtained.The results of paper chromatography,glucan gel chromatography and specific rotation for the purity identificationshowed that LPP1 a and LPP2 were of homogeneity.Monosaccharide composition analysis indicated that LPP1 a mainly consists of rhamnose,fucose,mannose and galactose;LPP2 is composed of five kinds of monosaccharide: rhamnose,fucose,mannose,galactose and glucose;Infrared spectral analysis results indicate that the glucose residues of LPP2 was?-dominating configuration in pyranose form sugar,LPP1 a is a kind of polysaccharides containing amino sugar spatialization,LPP2 contained protonated carboxyl;Triple helical structure of determinationillustrated that LPP1 a and LPP2 did not contain triple helical structure.LPP1 a and LPP2 have a certain antioxidation effect,both of the two litchi polysaccharides have a clear scavenging effect to DPPH,OH radicals.At the same time,antioxidation activities was positively related to the concentration of four litchi polysaccharides.Methylation research shows that: LPP1 a is mainly composed of?-L-Rhap-(1?,(1?2)-?-D-Gal and ?3,6)-?-D-Galp-(1? residues,the corresponding mole ratio of composition was as follows: 21.0:12.2:9.5.In addition,LPP1 a also contained mannose and fucose sugar residues.The glycosidic bond types and mole ratio of LPP2 are different from LPP1 a,LPP2 is mainly composed of?3,6)-?-D-Galp-(1?,(1?2)-?-D-Gal and(1?4,6)-?-D-Glcresidues,the mole ratio is 20.8:15.6:15.3.