Cytochalasins and orsellinic acid derivatives with cytotoxicity from the soil-derived fungus Trichocladium asperum.

Four undescribed cytochalasins (1-4), three undescribed orsellinic acid derivatives (5-7) and two known metabolites including methyl lecanorate (8) and methyl orsellinate (9) were isolated from the solid-state cultivation of a soil-derived fungus Trichocladium asperum SQ2-3 collected in Qinghai-Tibet Plateau. Their structures were elucidated by analysis of NMR (1D and 2D) and mass spectrometry data. The absolute configurations of 1-7 were assigned by a combination of the modified Mosher's method, microscale derivatization and Mo(OAc)-induced circular dichroism experiment. Compounds 1, 2, 3 and 6 showed significant cytotoxicity against HL-60, A3494, SMMC-7721, MDA-MB-231 and SW480 cell lines with IC values ranging from 4.74 to 15.84 μM, respectively. Meanwhile, compound 1 could obviously damage mitochondrial membrane potential and induce G2/M cell cycle arrest in A549 cells.