Full Length Research Paper

Antioxidant activity of aqueous extract of a Tolypocladium sp. fungus isolated from wild Cordyceps sinensis

Li Ping Zheng¹, Li Wen Gao², Jian Qin Zhou², Yang Hu Sima³ and Jian Wen Wang²*

¹Department of Horticultural Sciences, Soochow University, Suzhou 215123, P.R. China.

²School of Pharmaceutical Sciences, Medical College, Soochow University, Suzhou 215123, P.R. China.

³School of Pre-clinical Medicine and Life Sciences, Medical College, Soochow University, Suzhou 215123, P.R. China.

*Corresponding author. E-mail: jwwang@suda.edu.cn. Tel: +86 512 65880025. Fax: +86 512 65880031.

Accepted 23 July, 2008

Tolypocladium sp. Ts-1 was isolated from the fruiting body of a wild Cordyceps sinensis, one of the best known traditional Chinese medicine and health foods. The antioxidant activities of hot-water extracts from cultured mycelia of Tolypocladium sp. were assessed in different in vitro systems. The extracts showed superoxide dismutase (SOD) activity of 35.6 U/mg protein and are effective in scavenging superoxide radical in a concentration dependent fashion with IC₅₀ value of 1.3 mg/mL. As a reinforcement of the action, similar radical scavenging effects of the extracts were also discerned with both site-specific and non site-specific hydroxyl radical using the deoxyribose assay method. 1,1-Diphenyl-2-picrylhydracyl (DPPH) radical scavenging activities of the extracts reached more than 75.2% at the concentrations of 3-6 mg/mL. The extracts showed moderate reducing power and ferrous ion chelating activity. Moreover, the protective effects of the extracts against hydrogen peroxide (H₂O₂)-induced lesion to rat PC12 cell (pheochromocytoma cell line) was observed in a dose-dependent manner from 0.25 to 2.0 mg/mL. Our results suggest that the aqueous extract of Tolypocladium sp. mycelium has strong antioxidant activities and is a potential source of natural antioxidant products. This is the first report on antioxidant activity of Tolypocladium fungus isolated from wild C. sinensis, an endangered species.

Key words: Aqueous extracts, antioxidant activity, free radicals, PC12 cells, Tolypocladium sp.