Three new polyketides, eutyketides A and B ( and ) and cytosporin X (), along with four known compounds (-), were obtained from the marine-derived fungus . The planar structures of and were elucidated by extensive HRMS and 1D and 2D NMR analyses. Their relative configurations of C-13 and C-14 were determined with chemical conversions by introducing an acetonylidene group. The absolute configurations of - were determined by comparing their experimental electronic circular dichroism (ECD) data with their computed ECD results. All of the isolated compounds were tested for their anti-inflammatory activities on lipopolysaccharide-induced nitric oxide production in RAW 264.7 macrophages. Compounds and showed stronger anti-inflammatory activities than the other compounds, with the inhibition of 49.0% and 54.9% at a concentration of 50.0 µg/mL, respectively.