Fractionation, characterization and antioxidant activity of exopolysaccharide from fermentation broth of a Xylaria nigripes
2018
Chang, Chao-Kai | Ho, Wai-Jane | Chang, Shih-Liang | Yeh, Ching-Hua | Liang, Zeng-Chin | Hsu, Tai-Hao | Hsieh, Chang-Wei
In the present study, three main polysaccharide fractions, Xn-40, Xn-50, and Xn-80, were purified from fermentation broth cultures of Xylaria nigripes (Xns) by fractional precipitation with gradient concentrations of ethanol (40%, 50%, and 80%). In vitro antioxidant assay showed that Xn-40 was stronger than the others. The IC50 value of DPPH radical scavenging was 1,300 mg/L, and ABTS radical scavenging was 699.16 mg/L, respectively. Its functional group features were determined by Fourier transform-infrared spectroscopy (FT-IR). The results revealed the general characteristic absorption peaks of polysaccharides. We further investigated the antioxidant activity on human keratinocyte (HaCaT) cells. Our data demonstrated that polysaccharides of Xns had no cytotoxicity on HaCaT cells. Moreover, Xn-40 can significantly reduce AAPH-induced generates reactive oxygen species (ROS) generation in vitro. Comprehensive analysis results indicate that graded ethanol precipitation can effectively separate the polysaccharides that have antioxidant activity and Xns could be explored as a natural antioxidant.
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