Activity guided fractionations led to the isolation of two antitumor compounds 5a,8a-epidioxy-24(R )-methylcholesta-6,22-dien-3b-D-glucopyranoside and 5,6-epoxy-24(R )-methylcholesta-7,22-dien-3b-ol from the methanol extract of Cordyceps sinensis. Two previously known compounds, ergosteryl-3-O-b-D-glucopyranoside and 22-dihydroergosteryl-3-O-b-D-glucopyranoside were also isolated. The structures of hitherto unknown sterols were established by 1D and 2D NMR spectroscopic techniques with the former synthesized in order to con®rm the identity of the sugar moiety by chemical correlation. The glycosylated form of ergosterol peroxide was found to be a greater inhibitor to the proliferation of K562, Jurkat, WM-1341, HL-60 and RPMI-8226 tumor cell lines by 10 to 40% at 10 mg/ml than its previously identi®ed aglycone, 5a,8a-epidioxy-24(R )-methylcholesta-6,22-dien3b-ol. #

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