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.