Chetracins E and F, cytotoxic epipolythiodioxopiperazines from the marine-derived fungus Acrostalagmus luteoalbus HDN13-530

Two new epipolythiodioxopiperazines, named chetracins E and F ( 1 and 2 ), along with the known chetracin C ( 3 ), were isolated from the fungus Acrostalagmus luteoalbus HDN13-530. Their structures were elucidated based on the NMR, MS and CD data, as well as chemical conversion. All of the compounds exhibited cytotoxicity against the tested five cancer lines in low-micromolar or nanomolar IC 50 values. The computational docking indicated that compounds 1–3 could bind to the C-terminal of heat shock protein 90 (Hsp90), which was in line with the experimental observation of decreases in levels and active forms of Hsp90 client proteins.