Three new compounds, namely tumonoic acids K (1), L (2), and methyl 2-(2-acetyl-3,5-dihydroxy-4,6-dimethylphenyl)acetate (3), together with nine known compounds, were isolated from the marine-derived fungus Penicillium citrinum. The structures of these compounds were elucidated by spectroscopic methods and chemical derivatization. This study is the first to report on tumonoic acid analogues derived from a fungus.It has been demonstrated that marine fungal species have evolved unique metabolic mechanisms where the metabolites have potential applications in drug discovery.1 During the continuing research of antitumor natural products produced by Penicillium citrinum collected from the Min River estuary of China,2 we found that the extract of fermentation broth and mycelia showed potent cytotoxic activity against the A-375 cell. Therefore, we investigated the secondary metabolites of this fungus, and obtained two new tumonoic acid analogs, tumonoic acids K (1) and L (2), a new benzene derivative methyl 2-(2-acetyl-3,5-dihydroxy-4,6-dimethylphenyl)acetate (3), as well as nine known compounds including penicillenols A1, A2, B1, and B2 (4–7),3 dihydrocitrinone (8),4 phenol A acid (9),4 7-carboxyl-6,8 dihydroxy-1,1,3,4,5-pentamenthylisochroman (10),5 1-acetonyl-7-carboxyl-6,8-dihydroxy-3,4,5 trimethylisochroman (11),5 and 2,4,5-trimethylbenzene-1,3-diol (12).6 It is exciting to note that our group is the first to report the isolation of tumonoic acids from a fungus, whereas all of the previous reports of tumonic acids were derived from marine cyanobacterium.7,8