Cytochalasin P1, a new cytochalasin from the marine-derived fungus Xylaria sp. SOF11.

A new cytochalasin, named cytochalasin P1 (1), together with four known analogs (2-5) was isolated from marine-derived fungus Xylaria sp. SOF11 from the South China Sea. The structure of the new compound was elucidated on the basis of MS and NMR (1H, 13C, HSQC, HMBC, and NOESY) data analyses. Compounds 1-5 were tested for their cytotoxicities against four tumor cell lines (SF-268, MCF-7, NCI-H460, and HepG-2). Compounds 1-5 showed significant cytotoxicity against two tumor cell lines MCF-7 and SF-268, with the IC50 values varying between 0.33 and 4.17 μM.