Characterization And Their Bioactivities Of Polysaccharides From The Fruits Of Psidium Guajava Linn

This article systematically studied on the extraction, isolation, purification,structural characterization and biological activities of polysaccharides from the freshfruits of Psidium guajava Linn. The fresh fruits of Psidium guajava Linn wereextracted by hot water, precipitated by different concentration of ethanol. And theresidue was extracted by aqueous alkali, precipitated by ethanol. Finially four parts ofpolysaccharides were obtained. After removal of proteins, dialysis and lyophilization,the carbohydrate content of the four parts of curde polysaccharides were62.7%，70.3%，31.6%，21.6%. Each part of polysaccharides was isolated and purified byDEAE-52Cellulose chromatography，and nine polysaccharides named P50-1, P50-2,P70-1, P70-2, P70-3, P90-1, P90-2, AP-1and AP-2were obtained. After furtherpurification by Sephacryl S-100HR, Sephacryl S-300HR and Sephadex G-75gelfiltration, GP50-1, GP70-1, GP70-2, GP70-3, GP90-1A, GP90-1B, GP90-2andGAP-1were obtained. Optical rotation identification, performance gel permeationchromatography, ultraviolet spectroscop, high performance liquid chromatography,gas chromatography, methylation analysis, infrared spectroscopy and nuclearmagnetic resonance spectroscopy were performed for structure analysis of thehomogenous polysaccharides. The Optical rotation [α]25Dof the homogenouspolysaccharides (GP70-2, GP70-3, GP90-1A, GP90-1B, GP90-2and GAP-1) were+101°,+90°,-72°,+234°,-71°and-249°. The average Mw was7.4×104,10.6×104, 1.4×104,13.7×104,>140×104and6.9×104Da, separately. GP70-2is composed ofgalactose and arabinose. The structure of GP70-2comprises a backbone of (1â†'3)linked α-L-arabinofuranose and (1â†'3,6) linked β-D-galactopyranose with branchesconsisting of (1â†'6) linked β-D-galactopyranose and terminal β-D-galactopyranose.GP70-3is composed of rhamnose, glucuronic acid, galacturonic acid, galactose andarabinose. The structure of GP70-3comprises a backbone of (1â†'5) linkedα-L-arabinofuranose,(1â†'6) linked β-D-galactopyranose,(1â†'3) linkedβ-D-galactopyranose and (1â†'3,6) linked β-D-galactopyranose with branchesconsisting of (1â†'2,3,5)-α-L-arabinofuranose,(1â†'3)-α-L-arabinofuranose,(1â†'3)-β-D-rhamnopyranose,(1â†'3)-β-D-glucuronic acid,(1â†'3)-β-D-galacturonicacid, terminal β-D-galactopyranose. GP90-1A is a glucan composed of (1â†'6) linkedα-D-glucopyranose. GP90-1B is composed of glucose and arabinose. The structure ofGP90-1B comprises a backbone of (1â†'5) linked α-L-arabinofuranose,(1â†'3) linkedα-L-arabinofuranose,（1â†'2,3,5) linked α-L-arabinofuranose with the branchesconsisting of (1â†'6)-β-D-glucopyranose, terminal β-D-glucopyranose and terminalα-L-arabinofuranose. GAP-1is composed of mannose, rhamnose, glucuronic acid,glucose, galactose and arabinose. The structure of GAP-1comprises a backbone of(1â†'6) linked β-D-galactopyranose and (1â†'3,6) linked β-D-galactopyranose withbranches consisting of (1â†'2,3,5)-α-L-arabinofuranose,(1â†'3)-α-L-arabinofuranose,(1â†'5)-α-L-arabinofuranose,(1â†'3)-β-D-rhamnopyranose, terminal β-D-glucuronicacid, β-D-glucopyranose and β-D-mannopyranose. Determination of bioactivities：The results of DPPH radical scavenging activity shown that the scavenging effect ofGP70-2was47.6%at concentration of10mg/mL, GP70-3was16.5%at concentrationof1mg/mL, and GP90-1B was21.3%at concentration of9mg/mL. The results of OH radical scavenging activity shown that the scavenging effect of GP70-2was47.7%at concentration of9mg/mL, and GP70-3was32.3%at concentration of9mg/mL. GP70-2, GP70-3and GP90-2shown inhibitory effect on the activity of α-glucosidase, and the inhibition percentage were46.3%,39.8%and48.8%separatelyat concentration of5mg/mL.