Cytotoxic secondary metabolites from the endophytic fungus Aspergillus versicolor KU258497

Abstract

Two new isocoumarin dimers (1 and 2) and one new dihydroquinolone derivative (3) were isolated from Aspergillus versicolor, an endophyte derived from leaves of the Egyptian water hyacinth Eichhornia crassipes (Pontederiaceae), together with ten other known metabolites. Chemical structures of the isolated metabolites were determined based on HRESIMS, extensive 1D and 2D NMR spectroscopy. The relative and absolute configurations of the new natural products were established by ROESY and electronic circular dichroism (ECD) spectroscopy, respectively. The axial chirality of the isocoumarin 7,7′-homodimers (1 and 2) was deduced by TDDFT-ECD calculations. All isolated compounds were assessed for their antimicrobial, antitubercular and cytotoxic activities. Several tested compounds revealed significant cytotoxic activity against mouse lymphoma L5178Y cell line with IC50 values ranging from <0.36 to 16.3 μM.