Studies Onisolation, Purification Chemical Structure And Anti-Oxidant Activity Of Longan Polysaccharide

Objective:To extract and purify polysaccharide(LP-2)from Dimocarpus longan Lour and investigate its free radical,·OH scavenging abilities in vitro.To build up the methodology to measure the polysaccharide contents in Dimocarpus longan Lour and to analysis the molecular weight of LP-2.Methods:Crude polysaccharide was isolated by addition EtOH to the hot water extract of Dimocarpus longan Lour.The crude polysaccharide was further purified by DEAE-cellulose(OH~-)ion-exchange,Sephadex G-100 and Sepharose 4B.The molecular weight of LP-2 was determined by HPGPC. Chemiluminometry was employed to determine the ability of free radical scavenging of LP-2.Results:The LP-2 is a homogeneous polysaccharide,which molecular weight is 1.08×10~5.The monosaccharide constituent of LP-2 is only glucose.Its main chain is composed ofβ-(1→6)-linked-Glc residues possibly and the non-reduced end is Glc.LP-2 has the ability of scanvenging the·OH radical, which can be enhanced as the dose of polysaccharide increases,however,this ability is weaker than the thiourea's of the same concentration.Conclusion:The LP-2 is composed of D- glucopyranose.The main chain of LP-2 consists ofβ-(1→6)-linked-Glc residues possibly.Its molecular weight is 1.08×10~5.LP-2 can scavenge the·OH radical but not obviously.