We have focussed our attention on new antitumor metabolites from microorganisms which inhabit the marine environment. As part of this program, we have found that a strain of Penicillium waksmanii Zaleski OUPS-N133 separated from the brown alga Sargassum ringgoldianum produces two novel compounds, pyrenocines D (1), and E (2), along with the known compounds, two pyrenocines A (3) and B (4), and three dioxopiperazine derivatives (5)~(7). We describe herein the isolation, structure elucidation and cytotoxicity of these metabolites.