Longan is one of the most popular subtropical fruits in Southeast Asia, because of its flavor and benefits to health. As one of the important active ingredients of longan pulp, polysaccharide LPIIa was obtained by hot water extraction, ion-exchange chromatography and gel filtration chromatography. Its physicochemical characterization and immunostimulatory effects on macrophages were then investigated. Structural analyses indicated that LPIIa was a 44.7 kDa heteropolysaccharide mainly composed of →6)-Glc-(1→, →5)-Ara-(1→, →4)-Man-(1→and →6)-Gal-(1→. It en...