Sulfur compounds from the mushroom Boletus pseudocalopus and their bioactivity

In our continuing search for structurally interesting and bioactive metabolites from Korean wild mushrooms, we have collected scores of endemic Korean mushroom species in the mountainous areas during the hot humid summer and prepared MeOH extracts of them for antitumor-activity screening test. Among the collected wild mushrooms, the extract of Boletus pseudocalopus (Boletaceae) showed significant cytotoxicity against three human tumor cell lines. This mushroom is an inedible mushroom with toxicity that is recognized by its yellow fruiting bodies and the blue staining when the fruit-bodies are cut or brushed. Recently, we reported the identification of three new fatty acid esters with cytotoxicity. In continuing study on this mushroom, two sulfur compounds (1–2) together with four known compounds (3–6) were isolated from the n-BuOH-soluble fraction. The chemical structures of the new compounds were determined on the basis of 1D and 2D NMR spectroscopic data. The isolated compounds were evaluated for cytotoxicity against some human tumor cell lines using a SRB assay.