Panapophenanthrin, a Rare Oligocyclic Diterpene from Panus strigellus .

During the course of our search for biologically active secondary metabolites from fungal cultures, a new oligocyclic diterpenoidal derivative, panapophenanthrin ( 1 ), was isolated from Panus strigellus . In addition, two known metabolites, panepophenanthrin ( 2 ) and dihydrohypnophilin ( 3 ), were also obtained. The chemical structures of the isolated compounds were elucidated based on extensive 1D and 2D NMR spectral analyses together with high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). The absolute configuration was determined through TDDFT-ECD calculations. All of the compounds were assessed for their antimicrobial and cytotoxic activities. Compounds 1 and 3 showed moderate to weak activities in the performed antimicrobial assays, while compound 1 exhibited potent cytotoxic activity against the mammalian cell lines mouse fibroblast (L929) and human endocervical adenocarcinoma (KB3.1).