Cytotoxic grifolin derivatives isolated from the wild mushroom Boletus pseudocalopus (Basidiomycetes)

Activity-guided purification of a MeOH extract of the Korean wild mushroom Boletus pseudocalopus afforded three new grifolin derivatives, 1-3, along with four known phenolic compounds 4-7. Their structures were established by a combination of 1H- and 13C-NMR, NOESY, and extensive two-dimensional NMR spectroscopic experiments such as gCOSY, gHSQC, gHMBC, and ROESY. The major metabolites 4 and 5 were subjected to reduction to provide the side chain-reduced compounds 8 and 9 for biological testing. All of the compounds except compound 6 showed anticancer activities in the range of IC(50) 3.5-11.0 microg/ml against human lung carcinoma A549 and mouse melanoma B16F1 cell lines. In addition, all compounds showed moderate radical-scavenging activities determined by DPPH assay.