Cytotoxic Metabolites from the Antarctic Psychrophilic Fungus Oidiodendron truncatum

Two new epipolythiodioxopiperazines, named chetracins B and C (1 and 2), and five new diketopiperazines, named chetracin D (4) and oidioperazines A-D (5, 10, 12, and 13), were isolated from the fungus Oidiodendron truncatum GW3-13, along with six known compounds (3, 6, 7, 8, 9, and 11). Their structures were elucidated by extensive NMR, MS, and CD analyses, as well as chemical transformation. An in vitro MTT cytotoxicity assay revealed potent biological activity for 1 in the nanomolar range against a panel of five human cancer lines.