Metabolites isolated from Penicillium palitans, obtained from deep sea sediments in the maritime Antarctica, were investigated for phytotoxic and antifungal activities. The fungus was submitted to solid state fermentation, and its crude extract was produced. Chromatographic separations of the P. palitans methylene chloride crude extract led to the isolation of two analogous compounds: (-)-penienone (1) and (-)-palitantin (2). The phytotoxic activity of these compounds was assessed against seeds of Lactuca sativa and Agrostis stolonifera. Both compounds demonstrated activity exclusively in the monocotyledonous model, A. stolonifera. At a concentration of 1 mg mL