Eight undescribed quinolone alkaloids, pesimquinolones A - H, as well as six known compounds, were isolated from the solid culture broth of the fungus Penicillium simplicissimum. Their chemical structures were characterized by combined analyses of NMR spectroscopy and single-crystal X-ray crystallography. Pesimquinolones A - G are the first examples of naturally occurring quinolone alkaloids possessing a limonene moiety. Their antiinflammatory activities on LPS-induced nitric oxide (NO) production in adherent cells were evaluated. Pesimquinolones A, E, G, and H showed promising suppressive effect on the production of NO with IC50, values of 1.94, 1.29, 1.20, and 1.23 mu M, respectively.