Discovery of Oxidized p -Terphenyls as Phosphodiesterase 4 Inhibitors from Marine-Derived Fungi.

Four new p -terphenyl derivatives, talaroterphenyls A-D ( 1 - 4 ), together with three biosynthetically related known ones ( 5 - 7 ), were obtained from the mangrove sediment-derived Talaromyces sp. SCSIO 41412. Compounds 1 - 3 are rare p -terphenyls, which are completely substituted on the central benzene ring by oxygen atoms; this is the first report of their isolation from natural sources. Their structures were elucidated through NMR spectroscopy, HRESIMS, and X-ray diffraction. Genome sequence analysis revealed that 1 - 7 were biosynthesized from tyrosine and phenylalanine, involving four key biosynthetic genes ( ttpB - ttpE ). These p -terphenyls ( 1 - 7 ) and 36 marine-derived terphenyl analogues ( 8 - 43 ) were screened for phosphodiesterase 4 (PDE4) inhibitory activities, and 1 - 5 , 14 , 17 , 23 , and 26 showed notable activities with IC 50 values of 0.40-16 μM. The binding pattern of p -terphenyl inhibitors 1 - 3 with PDE4 were explored by molecular docking analysis. Talaroterphenyl A ( 1 ), with a low cytotoxicity, showed obvious anti-inflammatory activity in LPS-stimulated RAW264.7 cells. Furthermore, in the TGF-β1-induced medical research council cell strain-5 (MRC-5) pulmonary fibrosis model, 1 could down-regulate the expression levels of FN1, COL1, and α-SMA significantly at concentrations of 5-20 μM. This study suggests that the oxidized p -terphenyl 1 , as a marine-derived PDE4 inhibitor, could be used as a promising antifibrotic agent.