Physicochemical Properties And Antioxidant Activities Of Polysaccharides And Chemical Modifications From Amana Edulis

In this paper,Amana edulis polysaccharides?AEPs?specifically HBSS,CHSS,DASS,and CASS were sequentially extracted with four different solvents.Physicochemical properties,rheological,and antioxidant properties of these four polysaccharides were comparatively analyzed which lay a foundation for developing the AEPs polysaccharides and their respective modified fractions as potential functional food.Four kinds of polysaccharides were obtained from the whole plant which were continuously treated by four kind of solutions.Based on unique peak in UV absorption,four polysaccharides had a single component.Based on their absorptions around 3390cm^-1and 1400cm^-1by the fourier transform infrared spectrometer,these fractions were confirmed to be polysaccharides.The molecular weights of four AEPs were calculated to be around 6.29×10²?HBSS?,1.5×10²?CHSS?,8.1×10²?DASS?,and 2.6×10³k Da?CASS?by HPLC,respectively.According to gas chromatography analysis,rhamnose and arabinose were the main monosaccharides in HBSS.CHSS was mainly composed of arabinose and galactose.The monosaccharides that make up DASS were arabinose and galactose.CASS was mainly composed of rhamnose and galactose.Scanning electron micrographs of AEPs depicted the different microstructures.HBSS showed the maximum solubility,while,CASS was observed for higher foam capacity and foam stability.Among all the fractions,DASS was observed with higher thermal stability.The emulsifying activity and stability were enhanced as the concentration of the four AEPs increased.The emulsifying activity and stability of the AEPs were steady within the p H range of 2–10 and Na Cl concentration range of 0–0.4 mol/L.Among the four AEPs,DASS and HBSS showed the highest emulsifying activity and stability,respectively.The rheological properties of four AEPs polysaccharides?HBSS,CHSS,DASS,and CASS?were investigated under various concentrations,temperatures,p H levels,and ionic strengths.The apparent viscosities of the four AEPs solutions at 1%?w/w?concentration were found to be in the following order:CHSS>DASS>HBSS>CASS.When the AEPs were heated to 100°C,they showed lower colloidal viscosity,whereas after refrigeration and chilling,higher apparent viscosities were observed.The minimal apparent viscosity change of CASS at different temperatures indicated that CASS have good thermal stability and freeze-thaw stability.The apparent viscosity of four AEPs at p H 10 or p H 4 was lower than that at p H 7.DASS was least affected by p H change among four AEPs.The apparent viscosity increased at a lower sodium ion concentration and then declined with an increase in ion concentration.The decrease of HBSS was most pronounced among four AEPs.The storage modulus?G??and loss modulus?G??increased with an increase in oscillation frequency.All of these four AEPs exhibited good viscoelasticity.These four polysaccharides extracted from A.edulis have different antioxidant abilities.HBSS showed the highest ABTS⁺scavenging activity.HBSS and CASS had higher DPPH and OH^–scavenging activities.DASS depicted the highest chelation and reducing ability.Further,four sequentially extracted polysaccharides AEPs were modified by sulphation,phosphorylation,and carboxylation modifications?S-AEPs,P-AEPs,C-AEPs?,and investigated for their anti-oxidant activities.After modification,sugar and protein contents were decreased and uronic acid content was increased in comparison to native AEPs.UV absorption showed similar maximum absorption peaks of modified derivatives which indicated their homogeneous nature.FTIR spectra confirmed the conversion of hydroxyl groups to O-S,-COO,and P-OH bonds,respectively.The phosphorylated derivatives?P-AEPs?displayed the highest DPPH,hydroxyl radical,and ferrous ions radical scavenging abilities.Sulfated polysaccharides?S-AEPs?were observed with high reducing ability.The C-AEPs maintained the stable antioxidant properties after carboxylation modification.In DPPH clearance test,CHSS increased the most after three chemical modifications.However,for ABTS free radical scavenging,all the four polysaccharides showed significant improvements after modification.In the hydroxyl radical scavenging,the clearance rate before and after DASS modification was the smallest.For total reduction,HBSS changed most significantly after three modifications.Our results indicated that the chemical modification of different polysaccharide components had significantly affected their antioxidant potential as well as indicated their suitability in food industry and human health.