Cordyceps sinensis(Cs) or Dongchongxiacao in Chinese is a rare and precious medicinal mushroom.In this work,a Tolypocladium sp. fungus named Cs-HK1 was isolated from a natural Cs fruiting body,and its ultraviolet(UV),infrared(IR) and high-performance liquid chromatography(HPLC) spectra all exhibited high degrees of matching to those of natural Cs,indicating the similarity of chemical composition. A crude polysaccharide(PS) fraction isolated from Cs-HK1 fungal mycelium showed significant antitumor activity,inhibiting melanoma tumor growth in mice. The PS-treated mice showed significantly higher serum interferon-γ(IFN-γ)level and higher proliferation rate of lymphocytes ex vivo than the control animals,suggestive of the immunomodulatory activity of the PS fraction. In cell cultures,the PS fraction caused a significant and dose-dependent inhibitory effect on the proliferation of two cancer cell lines,B16/neu mouse melanoma and MDA-MB-231human breast cancer cells,but not on normal spleen lymphocytes in vitro. Most of these bioactivities of the CsHK1 fungus were comparable to or even greater than those of natural Cs. The results showed that Cs-HK1 fungus may be a functional substitute for the natural Cs in health food and herbal medicine.
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