Physicochemical Properties Of Mulberry Leaves Polysaccharides Extracted Using Different Solvents And Mixed System With Gelatin

Mulberry leave is one of edible and traditional Chinese medicines which contain high amount of ingredients including phenolics,flavonoids.The polysaccharides participate in anticancer,antidiabetics,anti-atherosclerosis,antibacterial and antioxidation.In present study,four different types of polysaccharides were isolated using hot buffer,chelating agent,diluted alkaline buffer,and concentrated alkaline buffer from mulberry leaves,and named as HBSS,CHSS,DASS,and CASS,respectively.The composition,structure,thermodynamic characteristics,rheological properties of the four polysaccharides were investigated.In addition,the physical and physiological activities,antioxidation,antibacterial,and anti-inflammatory of these polysaccharides were furtherly investigated.The potential,particle size,and rheological properties in the mixtures of polysaccharides and protein gelatin were analyzed.The results in present research provide theoretical evidences for application of extracted polysaccharides in the development of functional foods,medicinal product,and cosmetics.The key results of this study were listed as follows:(1)There are differences in composition and structure of four types of polysaccharides from mulberry leaves.All the polysaccharides extracted from mulberry leaves are acidic types;however,their composition and structures were varied.The molecular weights of HBSS,CHSS,DASS,and CASS were 7.812×103,3.279×103,6.912×103,and 1.408×103kDa,respectively.The total amount of sugar contents of four polysaccharides accounted for 82.31%,78.42%,80.30%,and 85.46%,respectively.All four heteropolysaccharides consisted with arabinose,rhamnose,mannose,xylose,glucose,and galactose.Among of them,HBSS had the highest content(27.07%)of galactose,while CHSS had the highest content of arabinose(30.55%).The glucose content was highest in DASS and CASS with 24.69%and 27.51%,respectively.In addition,22.76%of galactose content was detected in CASS.The uronic acids contents were 12.4%in HBSS,22.9%in CHSS,14.7%in DASS,and 20.8%in CASS,respectively.There were three different surface microstructures in the four polysaccharides,i.e.,uneven surface with irregular geometrical shape;lamellar structure with holes;disordered fiber structure,indicating that the different methods applied in extraction will affect the structure of polysaccharides.(2)The antioxidant,bacteriostatic and anticoagulant activities of four mulberry leaf polysaccharides were different.In the comparison of antioxidation among the four polysaccharides from mulberry leaves,it was found that CHSS had the lowest ability in clearing DPPH and ABTS but with significant effects in clearing of hydroxul radicals and chelating with Fe2+.The antibacterial ability of four polysaccharides was correlated with the concentration.The antibacterial activities of the four polysaccharide was validated in the order as CHSS>DASS>CASS>HBSS.The four polysaccharides had a stronger antibacterial ability in Gram-negative bacteria liking E.coli or S.typhimurium than that on Gram-positive bacteria(i.e.,B.subtilis,and S.aureus).Four polysaccharides had anticoagulant abilities through intrinsic and common coagulation pathways.Our study also found that the exogenous coagulation way could not accomplish the full process of anticoagulant activity.The CHSS showed the strongest anticoagulant function in the prolongation thrombin time(TT)and activated partial thromboplastin time(APTT).(3)Thermal and rheological properties of four mulberry leaf polysaccharides.CASS shows the best stability of thermodynamic in four tested polysaccharides.They showed thinning behavior in the analysis of rheology,indicating as typical non-Newtonian fluid property.In detail,the apparent viscosity of four polysaccharides was performed in this order:DASS>CHSS>HBSS>CASS.The apparent viscosity of polysaccharides was increased when the dosage was increased.However,the apparent viscosity of polysaccharides decreased when the temperature increased.CASS can stay with higher apparent viscosity in certain higher temperature.When the temperature increased to?60?,the rheological activities of CHSS?DASS,and CASS show typical Newtonian fluid property and HBSS showed typical non-Newtonian fluid property in our test.After heat treatment,the apparent viscosities of HBSS and CASS have significant decreasing.In turn to cold treatment,the apparent viscosity of four polysaccharides were increased.Interestingly,there is no significant change of apparent viscosity in DASS no matter under heat or cold treatments.The pH value had an adverse effect on the apparent viscosity of these four polysaccharides.The apparent viscosities of HBSS and CHSS were stable under the alkaline solution,while there were significant changes on DASS and CASS.Accompanying with the increased Ca2+concentration,the apparent viscosities of polysaccharides of HBSS and CASS were also increased.By the meantime,the apparent viscosities of polysaccharides were decreased in CHSS and DASS.The apparent viscosity showed a similar changing under the different concentration treatments of Na+in four polysaccharides.Taken these together,our results indicated that the four polysaccharides for mulberry leaves were viscoelastic materials,and at low frequency,the HBSS showed viscosified activity with concentration of 5mg/ml.The four polysaccharides showed elastic behavior at high frequency.(4)The physicochemical properties of Polysaccharide-Gelatin mixtures.In polysaccharide and gelatin system,the G-polysaccharides were clarified under the acidic treatment.However,under alkaline,G-HBSS and G-CHSS were clarified but G-DASS and G-CASS became turbid from clarification.The Zeta potential changed from positive to negative with the increase of pH.When the pH=7.0,Zeta potential of the G-polysaccharides increased with the increasing of MLPs concentration.No significant influence of the gelation form in the four mulberry leaf polysaccharides.The particle sizes of G-HBSS and G-CHSS decreased when pH increased,however,the particle sizes of G-DASS and G-CASS increased.In this study,we found that the variation of concentration only affected the distribution but not the size of particle.The four gelatin-mulberry leaf polysaccharide mixtures showed thinning behavior.The addition of gelatin induced the reduction of apparent viscosity of the four polysaccharides.The mixture of G-CHSS showed the best stability with relatively thickening phenotype.The apparent viscosity of G-CHSS and G-DASS decreased under acidic and alkaline Treatments.The apparent viscosity of G-CASS increased with the increasing Na+concentration.The apparent viscosities of G-HBSS,G-CHSS and G-DASS mixtures decreased with the increases of Na+concentration.The apparent viscosities of G-HBSS and G-DASS mixtures increased abnormally at 0.2 mol/ml and 0.4 mol/ml,respectively.The apparent viscosity of G-HBSS decreased after cold and heat treatment,while that of G-DASS and G-HBSS increased after cold and heat treatment.These results indicated that G-CASS was more suitable as a stabilizer in freezing process.G-CHSS is transformed from shear thinning to shear thickening in expansive fluid after cold and heat treatment.Dynamic oscillation shear tests show that G-HBSS showed elastic properties with concentrations of 5 mg/ml and 10 mg/ml.All the four G-polysaccharides showed viscosified activity viscous with the increasing of oscillation frequencies.