Cytotoxic Cytochalasin Metabolites of Endophytic Endothia gyrosa

In addition to the known metabolites cytochalasin H ( 1 ), cytochalasin J ( 2 ), and epoxycytochalasin H ( 3 ), two new 10‐phenyl‐(11)‐cytochalasans, named cytochalasin Z10 and Z11 ( 4 and 5 , resp.) were isolated from the solid substrate culture of Endothia gyrosa IFB‐E023, an endophytic fungus residing inside the healthy leaf of Vatica mangachapo (Dipterocarpaceae). The structure determination of 4 and 5 was accomplished through correlative analyses of their spectral data (UV, ESI‐MS, IR, 1 H‐ and 13 C‐NMR, COSY, NOESY, HMQC, and HMBC). Metabolites 1 – 5 were demonstrated to be substantially cytotoxic to the human leukaemia K562 cell line with the IC 50 values of 10.1, 1.5, 24.5, 28.3, and 24.4 μ M , respectively, which are comparable to that of 5‐fluorouracil (33.0 μ M ), co‐assayed as the positive reference.