New pyridone alkaloids from marine-derived fungus Penicillium sp.

Abstract

Five new pyridone alkaloids Citridones H-L (1–5) along with one new natural product ent-Citridone A (6) were isolated from the marine-derived fungus Penicillium sp. XZD3-3, which came from the gut of a marine shrimp. The structures and absolute configurations of these compounds were elucidated on the basis of NMR, HRESIMS, UV, modified Mosher′s method, single-crystal X-ray diffraction, and ECD calculation. Compounds 1 and 3 contained unprecedented polycyclic systems of phenyl-pyranopyridone and phenyl-spiro[cyclopentene-furopyridone], respectively. Compound 2 showed moderate inhibition activity against nitric oxide production with IC50 value of 52.5 μM. All tested compounds were inactive in neither antibacterial nor cytotoxicity assays.