Four Ardeemin Analogs from Endophytic Aspergillus fumigatus SPS-02 and Their Reversal Effects on Multidrug-Resistant Tumor Cells

Four ardeemin derivatives, 5-N-acetylardeemin (1), 5-N-acetyl-15b-hydroxyardeemin (2), 5-N-acetyl-15b-didehydroardeemin (3), and 5-N-acetyl-16-hydroxyardeemin (4), were isolated from the fermentation broth of an endophytic Aspergillus fumigatus SPS-02 associated with Artemisia annuaL. The structures of these metabolites were elucidated by a combination of spectroscopic data, including 1D-, 2D-NMR and MS. In vitro chemosensitization assay indicated that these ardeemins had different activities of reversing the multidrug-resistant (MDR) phenotype in three cancer cell lines, leukemia doxorubicin resistant cell K562/DOX, human lung adenocarcinoma cis-platin-resistant cell A549/DDP, and ovarian cancer cisplatin-resistant cell SK-OV-S/DDP. Compound 4 exhibited the strongest MDR reversing effect at 5M concentration in K562/DOX and A549/DDP cell lines 5.2 +/- 0.18-fold, 8.2 +/- 0.23-fold, respectively, while compound 2 had the highest reversal capacity in SK-OV-S/DDP cell line with 10.8 +/- 0.28 fold. Preliminary investigation of their structureactivity relationship suggested that a OH group at C(15b) or C(16) in ardeemin plays a key role in reversing the MDR effect. It is the first report on ardeemin analogs from endophytic A. fumigatus with reversal effects on MDR cancer cell lines K562/DOX, A549/DDP and SK-OV-S/DDP.