Characterization of Cladosporols from the Marine Algal-Derived Endophytic Fungus Cladosporium cladosporioides EN-399 and Configurational Revision of the Previously Reported Cladosporol Derivatives

Four new cladosporol derivatives, cladosporols F–I ( 1 – 4 ), the known cladosporol C ( 5 ), and its new epimer, cladosporol J ( 6 ), were isolated and identified from the marine algal-derived endophytic fungus Cladosporium cladosporioides EN-399. Their structures were determined by detailed interpretation of NMR and MS data, and the absolute configurations were established on the basis of TDDFT-ECD and OR calculations. The configurational assignment of cladosporols F ( 1 ) and G ( 2 ) showed that the previously reported absolute configuration of cladosporol A and all the related cladosporols need to be revised from (4′ R ) to (4′ S ). Compounds 1 – 6 showed antibacterial activity against Escherichia coli, Micrococcus luteus, and Vibrio harveyi with MIC values ranging from 4 to 128 μg/mL. Compound 3 showed significant cytotoxicity against A549, Huh7, and LM3 cell lines with IC 50 values of 5.0, 1.0, and 4.1 μM, respectively, and compound 5 showed activity against H446 cell line with IC 50 value of 4.0 μM.