New Isocoumarin and Pyrone Derivatives from the Chinese Mangrove Plant Rhizophora mangle -Associated Fungus Phomopsis sp. DHS-11

Mangrove-associated fungi are important sources for the discovery of new bioactive natural products. Three new isocoumarins ( - ) and one new pyrone derivative ( ) were isolated from the ethyl acetate extract of the fermentation broth of the mangrove endophytic fungus sp. DHS-11. Nuclear magnetic resonance (NMR) spectroscopy (one-dimensional and two-dimensional) and mass spectrometry were used to determine the structures of these new compounds. The absolute configurations for the new isocoumarins - were determined by comparing their experimental and calculated electronic circular dichroism (ECD) spectra, while the configuration for the new pyrone-derivative was tentatively solved by comparison of its C NMR data with reported data. In the biological activity test, compounds and showed cytotoxic activity against HeLa cells with IC values of 11.49 ± 1.64 µM and 8.70 ± 0.94 µM, respectively. The initial structure and activity relationship (SAR) analysis revealed that the length of the side chain at C-3 for isocoumarin-type compounds - could affect the cytotoxicity against HeLa cells. Compound exhibited cytotoxic activities against human hepatoma cells HepG2 with an IC value of 34.10 ± 2.92 µM. All compounds have no immunosuppressive activity.