Atranones from Stachybotrys chartarum and their antitumor activities in MG-63 human osteosarcoma cells

Two new atranones T and U (1 and 2), and three known analogues atranone B (3), atranone Q (4), and stachatranone C (5) were isolated from the toxigenic fungus Stachybotrys chartarum. Their structures and absolute configurations were elucidated by spectroscopic data and calculated ECD analyses. The cytotoxicities of all the atranones (1-5) were evaluated against MG-63 human osteosarcoma cell lines. Compound 4 exhibited significant cytotoxic effect against MG-63 with IC₅₀ value of 8.6 μM, being more active than the positive control, 5-FU (IC₅₀ 10.4 μM). Morphological features of apoptosis activities were evaluated in 4-treated MG-63 cells. Compound 4 effectively induced apoptosis of MG-63, which was associated with G₀/G₁-phase cell cycle arrest. Flow cytometric analysis showed that the treatment by 4 significantly induced MG-63 cell apoptosis in a dose-dependent manner.