Exopolysaccharides from the fungal endophytic Fusarium sp. A14 isolated from Fritillaria unibracteata Hsiao et KC Hsia and their antioxidant and antiproliferation effects

Abstract

Exopolysaccharides (EPSs) are high-molecular-weight carbohydrates with a wide range of biophysiological activities, such as antioxidant activity, immunostimulatory activity, antitumor activity, hepatoprotective activity, and antifatigue effects. In the present work, two water-soluble EPSs, namely, A14EPS-1 and A14EPS-2, were isolated and purified from the fungal endophytic strain A14 using ethanol precipitation, DEAE-cellulose ion exchange chromatography and Sepharose G-150 gel filtration chromatography. A14EPS-1 (∼2.4× 104Da, the major fraction) was mainly composed of mannose, rhamnose, glucose, galactose, xylose and arabinose with a molar ratio of 0.31:0.55:10.00:0.34:0.03:0.06. The major monosaccharide of A14EPS-1 was pyranose, which was connected by α-glycosidic linkages. And the side chains of A14EPS-1 may be composed of rhamnose, arabinose, glucose and galactose; moreover, the backbone of A14EPS-1 may be composed of rhamnose, xylose, arabinose and glucose. A14EPS-2 (∼0.5× 104Da) was mainly composed of mannose, rhamnose, glucose, galactose, xylose and arabinose in a ratio of 0.16:0.88:10.00:0.39:0.06:0.06. Pyranose was observed in both the α- and β-configurations in A14EPS-2, and the α configuration was dominant. In addition, the results of the bioactivity assays indicated that both A14EPS-1 and A14EPS-2 had moderate antioxidant activity invitro, and A14EPS-2 showed a moderate antiproliferation effect on human hepatocellular carcinoma HepG2 cells.