Discovery of Structurally Diverse γ-Pyrone-Type Diterpenoids Produced by the Fungus Mariannaea sp. FKR-1011 from Zamami Island

Seven γ-pyrone-type diterpenoids, including four new compounds (candelalides D-G (1-4)) and three known compounds (candelalides A-C (5-7)), were isolated from the solid culture material of the fungus Mariannaea sp. strain FKR-1011, obtained from Zamami Island, Okinawa, Japan. The chemical structures and relative configurations of 1-4 were determined by spectroscopic analysis such as FT-IR, NMR, and HR-ESI-MS. The absolute configurations of 1-4 were determined through extensive spectroscopic data analysis and TDDFT-ECD calculations. The isolated compounds were tested for biological activity, revealing antibacterial activity against methicillin-resistant Staphylococcus aureus in combination with β-lactam antibiotics and antimalarial activity against Plasmodium falciparum K1 and FCR3 strains.