| Summary: | 碩士 === 大葉大學 === 生物科技碩士在職學位學程 === 103 === Xylaria nigripes as a precious medicinal fungus and earlier researches shows that X. nigripes polysaccharide has the ability in antioxidant, improving insomnia, immunomodulatory and other effects. This study was investigate that the antioxidant activity and composition of X. nigripes polysaccharide which separated by ethanol a precipitation. Four main polysaccharide fractions, XN-40, XN-50, XN-60 and XN-80 were purified from fermentation broth cultures of X. nigripes by fractional precipitation with gradient concentrations of ethanol (40%, 50%, 60% and 80%) and the antioxidant activities of different polysaccharide fractions were evaluated by ABTS radical scavenging, reducing power and DPPH radical scavenging assay in this study.The results indicated thatXN-40has the best effective on antioxidant assay. The IC50 value of ABTS radical scavenging was 699.16 mg/L, and DPPH radical scavenging was 1,300 mg/L, respectively. The FT-IR shows that XN-40 has more functional groups such as β-glycosidic linkage (890 cm-1), O-H bond (1650 cm-1), C-OH bending (1105 cm-1), C-O-C stretching(1047 to 1080 cm-1) which associated with antioxidant activity. Moreover, XN-40 (83.21%) exhibited the highest scavenging effect on ABTS radicals among all samples, followed by XN-60(81.26%), XN-80(75.91%) and XN-50(66.59%) at the concentration of 2,500 µg/mL.Further discussion of antioxidant activity on Human keratinocyte (HaCaT) cell in vitro that XN-40 cell viability about 86% that is 0.69 times than XN-80 at 200 µg/mL. Moreover, XN-40 can significantly reduce AAPH-induced ROS generation that is 0.84 times of XN-80 at 200 µg/mL. Comprehensive analysis results indicate that graded ethanol precipitation can effectively separate the polysaccharides which have antioxidant activity, so it can be widely applied in bioindustry.
Key Words: Xylaria nigripes, Extracellular polysaccharides, Alcohol precipitates,
Anti-oxidation, Component analysis
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