Alkaloids from the endophytic fungus Penicillium brefeldianum and their cytotoxic activities

One new indoloditerpene, 6,7-dehydropaxilline (1), one new indole-diketopiperazine, spirotryprostatin F (2), and one new 13-membered macrolide, N-demethylmelearoride A (3), as well as 8 known alkaloids (4-11), were isolated from the solid cultures of the endophytic fungus, Penicillium brefeldianum. The structures and absolute configurations of compounds 1-3 were elucidated by comprehensive spectroscopic analysis and the circular dichroism (CD) exciton chirality method. All the metablites were evaluated for their cytotoxic activites against three human tumor cell lines. Compound 2 exhibited cytotoxicities against HepG2 and MDA-MB-231 cells with IC₅₀ values of 14.1 μmol/L and 35.5mmol/L, respectively. Compound 3 showed moderate activity against HepG2 cells with IC₅₀ values of 36.6 μmol/L.