Indole-Diterpenoids with Protein Tyrosine Phosphatase Inhibitory Activities from the Marine-Derived Fungus Penicilliumsp. KFD28

Five new indole-terpenoids named penerpenes E–I (1–5), along with seven known ones (6–12), were isolated from the marine-derived fungus Penicilliumsp. KFD28 from a bivalve mollusk, Meretrix lusoria. The structures of the new compounds were elucidated from spectroscopic data and ECD spectroscopic analyses. Compound 1was assigned as an indole-diterpenoid with a unique 6/5/5/6/6/5/5 heptacyclic ring system. Compound 2represents an indole-diterpenoid with a new carbon skeleton derived from paxilline by the loss of three carbons (C-23/24/25). Compound 3contains an additional oxygen atom between C-21 and C-22 compared to paxilline to form an unusual 6/5/5/6/6/7 hexacyclic ring system bearing a 1,3-dioxepane ring, which is rarely encountered in natural products. Compounds 1, 2, 4, and 6showed inhibitory activities against protein tyrosine phosphatase 1B (PTP1B) with IC50values of 14, 27, 23, and 13 μM, respectively.