Antioxidant and Antiradical Activities of Wu Ling Shen in a Cell Free System

The present study aimed to investigate the antioxidant and antiradical activities of Wu Ling Shen, a popular medicinal fungus (Xylaria nigripes) used in traditional Chinese medicine preparations. Two different X. nigripes materials, the cultivated X. nigripes mycelia (XN) and a commercial X. nigripes product (XNP), were used to prepare the aqueous (XN-H vs. XNP-H) and ethanol (XN-E vs. XNP-E) extracts for this study. Polyphenol and total polysaccharide contents of these extracts were also examined. Results showed that extracts of XN possessed stronger antioxidant and antiradical activities than XNP in all tested model systems. However, all extracts exhibited a weak activity in metal chelation and reducing power. Total antioxidant activity of XN extracts (IC50 6.20 microg/ml for XN-H and 5.41 microg/ml for XN-E), but not XNP extracts (IC50 128.13 microg/ml for XNP-H and 96.16 microg/ml for XNP-E), was more potent than Trolox (IC50 19.64 microg/ml) and vitamin C (IC50 26.39 microg/ml). XN-E (IC50 5.12 microg/ml) and XNP-E (IC50 8.89 microg/ml) possessed a relatively similar potency as that of positive controls (IC50 6.94 microg/ml for Trolox and 4.25 microg/ml for vitamin C) in the superoxide radical scavenging activity. Although the DPPH radical scavenging of XN extracts was weaker than that of Trolox and vitamin C, it was about eight times more potent than that of XNP extracts. In ABTS assay, both XN and XNP extracts exhibited a moderate ABTS radical scavenging activity. Among the different extracts, XN-E showed the highest total flavonoid (32.69 mg/g) and phenol (59.75 mg/g) contents, while XNP-H (7.50% w/w) had the highest level in total polysaccharide content. These results conclude that XN-E possesses the most potent antioxidant and antiradical activities, and that these activities could be derived from its high polyphenol content, but not the level of polysaccharides.