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 mu M. All tested compounds were inactive in neither antibacterial nor cytotoxicity assays. (C) 2020 Elsevier Ltd. All rights reserved.