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 by extensive spectroscopic data, electronic circular dichroism calculations, and single X-ray diffraction analysis. All metabolites structures were characterized by a typical α,β-unsaturated ketone fragment and possess a higher oxidation degree. Multioketides A and B were a pair of epimer with a rare dihydroisobenzofuranone core. Multioketide C possessed a novel 5/6/6/6 heterotetracyclic chemical architecture featuring an unusual 1,4-dioxin functionalities. Plausible biosynthetic pathways for 1-6 were proposed. Additionally, compound 3 showed weak inhibitory activities on both acetylcholinesterase and protein tyrosine phosphatase 1B.