Antioxidative Indenone and Benzophenone Derivatives from the Mangrove-Derived Fungus Cytospora heveae NSHSJ-2.

Seven new polyketides, including four indenone derivatives, cytoindenones A-C ( 1 , 3 - 4 ), 3'-methoxycytoindenone A ( 2 ), a benzophenone derivative, cytorhizophin J ( 6 ), and a pair of tetralone enantiomers, (±)-4,6-dihydroxy-5-methoxy- α -tetralone ( 7 ), together with a known compound ( 5 ) were obtained from the endophytic fungus Cytospora heveae NSHSJ-2 isolated from the fresh stem of the mangrove plant Sonneratia caseolaris . Compound 3 represented the first natural indenone monomer substituted by two benzene moieties at C-2 and C-3. Their structures were determined by the analysis of 1D and 2D NMR, as well as mass spectroscopic data, and the absolute configurations of (±)- 7 were determined on the basis of the observed specific rotation value compared with those of the tetralone derivatives previously reported. In bioactivity assays, compounds 1 , 4 - 6 showed potent DPPH· scavenging activities, with EC50 values ranging from 9.5 to 16.6 µM, better than the positive control ascorbic acid (21.9 µM); compounds 2 - 3 also exhibited DPPH· scavenging activities comparable to ascorbic acid.