Cytotoxic isocoumarin derivatives from the mangrove endophytic fungus Aspergillus sp. HN15-5D.

Five isocoumarin derivatives including three new compounds, aspergisocoumrins A-C (1-3), together with two known analogues, 8-dihydroxyisocoumarin-3-carboxylic acid (4) and dichlorodiaportin (5) were obtained from the culture of the endophytic fungus Aspergillus sp. HN15-5D derived from the fresh leaves of the mangrove plant Acanthus ilicifolius. Their structures were elucidated using comprehensive spectroscopic methods. The double bond geometry of compounds 1 and 2 were assigned as E and Z on the basis of the distinct coupling constants, respectively. Compounds 1 and 2 showed cytotoxicity against MDA-MB-435 with IC50 values of 5.08 ± 0.88 and 4.98 ± 0.74 μM, respectively.