A New Cyclic Peptide and a New Steroid from the Fungus Penicillium sp. GD6 Isolated from the Mangrove Bruguiera gymnorrhiza

A rare new cyclic tetrapeptide, 5,5′‐epoxy‐MKN‐349A (1), featured by a MKN‐349A (5) skeleton and containing an uncommon ether bridge between C(5) and C(5′), and a new steroid, named 11‐O‐acetyl‐NGA0187 (2), together with two known steroids, 3 and 4, were isolated from an endophytic fungus Penicillium sp. GD6 associated with the Chinese mangrove Bruguiera gymnorrhiza. The structures of the new compounds were elucidated on the basis of extensive spectroscopic analyses and by comparison with the data of related compounds reported in literature. Neither of the compounds 3 and 4, isolated in this study, showed obvious bioactivities in the antibacterial bioassay experiments.