Multioxidized polyketides from an endophytic Penicillium sp. YUD17006 associated with Gastrodia elata

Three novel, highly oxygenated polyketides, multioketides A−C (1−3), and three previously described multioxidized aromatic polyketides (4−6), were isolated from an endophytic Penicillium sp. YUD17006 associated with Gastrodia elata. Their chemical structures were elucidated using extensive spectroscopic data, electronic circular dichroism calculations, and single X-ray diffraction analysis. All metabolites were characterized by a typical α,β-unsaturated ketone fragment and exhibited a high degree of oxidation. Multioketides A and B were identified as a pair of epimers featuring a rare dihydroisobenzofuranone core. Multioketide C possessed a novel 5/6/6/6 heterotetracyclic chemical architecture with unusual 1,4-dioxin functionalities. Plausible biosynthetic pathways for 1−6 were proposed. Additionally, compound 3 demonstrated weak inhibitory activities against both acetylcholinesterase and protein tyrosine phosphatase 1B.