A series of meroterpenoids with rearranged skeletons from an endophytic fungus Penicillium sp. GDGJ-285

Under the guidance of MS/MS based molecular networking, five new meroterpenoids (1-5), including three novel skeleton meroterpenoids, peniclactones A-C (1-3), and two new isoaustinone analogues, 6-hydroxyisoaustinone (4) and 6-ketoisoaustinone (5), were isolated from the fungus Penicillium sp. GDGJ-285. Their structures were elucidated by HRMS and NMR spectroscopy, and their absolute configurations were determined by X-ray single-crystal diffraction analysis. Peniclactones A-C (1-3) represent the first meroterpenoids featuring a 6/5/6/6/5/6 (1), 6/5/6/6/5/5 (2), and 6/5/6/5/5/6 (3) hexacyclic ring system, respectively. Bioassays showed that compound 3 inhibited nitric oxide production in lipopolysaccharide-induced RAW 264.7 macrophage cells with an IC50 value of 39.03 mM.