Six new isochroman derivatives (annulohypoxylomans A-C, 1-3; annulohypoxylomanols A and B, 6 and 7; and annulohypoxyloside, 8), an isocoumarin (annulohypoxylomarin A, 4), and an azaphilone derivative (xylariphilone, 5) were isolated from an ethyl acetate extract derived from cultures of the endophytic fungus JS540 found in the leaves of Zizania caduciflora. The JS540 strain was identified as Annulohypoxylon truncatum. The structures of the isolated compounds were elucidated by one- and two-dimensional nuclear magnetic resonance and mass spectrometry and by comparison with related compounds from the literature. The anti-inflammatory activities of the isolated compounds were evaluated in lipopolysaccharide (LPS)-stimulated bone marrow-derived dendritic cells. Xylariphilone (5) exhibited significant inhibitory effects on LPS-induced interleukin (IL)-6, IL-12 p40, and tumor necrosis factor (TNF)-α production with IC50 values of 5.3, 19.4, and 37.6 μM, respectively.