Talarmalnoids A-F: Fusicoccane diterpenoids from an arthropod-derived endophytic fungus Talaromyces malicola

The metabolites from the endophytic fungus Talaromyces malicola hosted in the gastrointestinal tract of the arthropods Armadillidium vulgare were investigated, and six undescribed fusicoccane diterpenoids, talarmalnoids A-F (1-6), along with three known analogs were isolated. Talarmalnoid C (3) was an unprecedented fusicoccane diterpenoid with two sugar units, i.e., 6-O-methyl-α-d-glucose and α-d-glucose. Talarmalnoids D and E (4 and 5) were fusicoccane-type diterpenoids with unusual seven-membered rings attached at the C-3' and C-4' positions. Their structures and absolute configurations were identified by NMR, HRESIMS analyses, X-ray single crystal diffraction, GC-MS, ECD analyses, ¹³C NMR calculations, and DP4+ probability analyses. Bioassay results showed that talarmalnoid B (2) exhibited significant inhibitory activities against the LPS-inducted production of NO in RAW 264.7 cells, with IC₅₀ value of 0.83 μM.