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 IC 50 value of 39.03 μM.