Isocoumarin Derivatives from the Sponge‐Associated Fungus Peyronellaea glomerata with Antioxidant Activities

Chemical examination of the solid culture of the sponge‐associated fungus Peyronellaea glomerata led to the isolation of five new isocoumarins, namely peyroisocoumarins A – D ( 1 – 4 ) and isocitreoisocoumarinol ( 5 ), together with 13 known analogues ( 6 – 18 ). Their structures were determined on the basis of extensive spectroscopic analyses, including the modified Mosher's method for the configurational assignments. Peyroisocoumarins A and B were characterized by the presence of Cl‐atom at pentane chain, which were unusual in isocoumarin derivatives. The ARE reporter assay revealed that peyroisocoumarins A, B, and D exerted potent ARE activation in HepG2C8 cells, while the preliminary analyses of structure–activity relationship was discussed.