Preparation,Physicochemical Properties And Antioxidant Activities Of Polysaccharides From Vaccinium Bracteatum Thunb. Leaves

Vaccinium Bracteatum Thunb.?VBT?leaves contain a variety of active ingredients.We have taken VBT leaves as raw material and sequentially extracted VBT leaves polysaccharides.This paper mainly examined component and physicochemical properties of VBT leaves polysaccharides,emulsifying,rheological and antioxidant properties.Furthermore,the above properties of four VBT leaves polysaccharide fractions were compared.As known,the extraction methods always bring about the diversification of property and functions of polysaccharides.The VBT leaves polysaccharides were sequentially extracted using hot buffer?HBSS?,chelating agent?CHSS?,dilute alkaline?DASS?and concentrated alkaline?CASS?.Based on their absorptions at 3600–3200 cm-1 and 1200–800 cm-1 by the fourier transform infrared spectrometer,these fractions were confirmed to be polysaccharides.Four polysaccharides fractions with respective molecular weights of 7.66×103,5.92×103,1.02×104,7.64×102 kDa by HPLC.HBSS consisted of arabinose,glucose and galactose.CHSS consisted of arabinose and galactose;DASS consisted of rhamnose and arabinose;CASS consisted of arabinose and glucose.Within the range of 20–300 °C,CHSS showed the highest peak temperature,whereas HBSS displayed the highest endothermic enthalpy.HBSS showed the highest emulsifying activity,and CASS displayed the longest emulsifying stability.The rheological properties of VBT leaves polysaccharides were investigated.The four VBT leaves polysaccharides in solution exhibited typical non-Newtonian shear-thinning behavior within the concentrations of 0.6–2.5%.The apparent viscosity of VBT leaves polysaccharides in solution decreased under following conditions: acidic pH?4.0?,alkaline pH?10.0?,in the presence of Ca²⁺ and at high temperature,while it increased in the presence of Na⁺ and at freezing conditions.The four VBT leaves polysaccharides also exhibited some variations in their antioxidant activities.For example,CASS showed the highest reducing power;CHSS showed the highest DPPH radical scavenging activity;HBSS exhibited the highest hydroxyl radical and ABTS radical scavenging activity;CHSS displayed the higher ferrous ions chelating ability than others.The above results of physicochemical properties and antioxidant activities of VBT leaves polysaccharides made it a potent candidate in functional foods.