New furoisocoumarins and isocoumarins from the mangrove endophytic fungus Aspergillus sp. 085242

The chemical investigation of the mangrove endophytic fungus Aspergillus sp. 085242 afforded eight isocoumarin derivatives 1 – 8 and one isoquinoline 9 . Asperisocoumarins A and B ( 1 and 2 ) were new furoisocoumarins, and asperisocoumarins E and F ( 5 and 6 ) were new isocoumarins. Their structures were established by analysis of their spectroscopic data and the absolute configuration of compound 2 was unambiguously determined by X-ray structure analysis and ECD calculation. Moreover, the absolute configurations of compounds 3 – 5 were assigned by comparison of their ECD spectra with isocoumarins described in the literature. Asperisocoumarins C and D ( 3 and 4 ) were fully characterized spectroscopically and isolated from a natural source for the first time. Asperisocoumarins A–D ( 1 – 4 ) related to the class of furo[3,2- h ]isocoumarins are rarely occurring in natural sources. Compounds 2 , 5 , and 6 showed moderate α-glucosidase inhibitory activity with IC 50 of 87.8, 52.3, and 95.6 μM, respectively. In addition, compounds 1 and 3 exhibited weak radical scavenging activity with EC 50 values of 125 and 138 μM, respectively.