Preliminary Physicochemical Characterization and Antioxidant Activity of Polysaccharide Fraction from Endophytic Fungal WBS020 Originated from Fritillaria unibracteata var. wabuensis

Abstract:

The exopolysaccharide extracted from the fermentation broth of endophytic fungal Fusarium tricinctum WBS020 originated from Fritillaria unibracteata var. wabuensis（FUW） was studied. At first，the crude polysaccharide was precipitated with ethanol from the fermentation broth after being degreased by organic solvent，and further were preliminary purified by macroporous resin methods for decoloration，proteases in combination with Sevag reagent methods for deproteinization，equilibrium dialysis methods for desalination in vitro，the DEAE cellulose DE-52 anion exchange chromatography and sephadex G-150 column chromatography methods for the separation of polysaccharide. Subsequently，homogeneity average relative molecular weight and monosaccharide composition of the purified polysaccharide were studied by the methods of high-performance gel permeation chromatography coupled with evaporative light scattering detection（HPGPC-ELSD），PMP（1-phenyl-3-methyl-5-pyrazolone） precolumn derivatization with high performance liquid chromatography coupled to photodiode array detector（PMP-HPLC-DAD），respectively. And partial physicochemical properties were also analyzed by ultra violet（UV） spectra and fourier transform infrared（FT-IR） methods. Finally，the antioxidant activities were determined by DPPH radical scavenging assay，ABTS radical scavenging assay and ferrous ion chelating activity assay. Results showed that WBS020EPS1-2，as the main exopolysaccharide，was obtained after the extraction，separation and purification. WBS020EPS1-2 was homogeneous exopolysaccharide with 95% purity and contained a small quantity of binding proteins，and was comprised of mannose，rhamnose，glucose，galactose and ara binose with a molar ratios of 0.43∶0.13∶10.00∶1.92∶0.11. Besides，there was a unknown monosaccharides. The monosaccharide in WBS020EPS1-2 was a pyranose，which was connected by an α-glycosidic linkage. The average relative molecular weight of WBS020EPS1-2 was approximately 3.137×104. In addition，exopolysaccharide WBS020EPS1-2 had a weak DPPH radical scavenging activity，while possessed a strong ABTS radical scavenging effect and a good ferrous ion chelating activity with the IC50 value of 1.93 mg/mL and 4.52 mg/mL，respectively.