Cytotoxic Epipolythiodioxopiperazines from the Deep-Sea-Derived Fungus Exophiala mesophila MCCC 3A00939.

Four new aranotin-type epipolythiodioxopiperazines, graphiumins K-N ( 1 - 4 ), along with four known analogues ( 5 - 8 ), were isolated from the deep-sea-derived fungus Exophiala mesophila MCCC 3A00939. Their structures were elucidated by detailed interpretation of NMR and mass spectrometric data. The absolute configuration of the isolates was deduced by a single-crystal X-ray diffraction analysis and the comparisons of experimental electronic circular dichroism (ECD) data with calculated ECD spectra. Graphiumins K ( 1 ) and L ( 2 ) exhibited cytotoxic activities against the K562, H69AR, and MDA-MB-231 cancer cells with IC 50 values ranging from 2.3 to 5.9 μM.