Recently, we found that the MeOH extract of Penicillium oxalicum showed inhibitory activity towards DNA topoisomerase I. Subsequently, ergosterol peroxide, ergosterol, palmitoleic acid, and linoleic acid were isolated from the cultured mycelia of A oxalicum. The structural determinations were based on physical and spectral analyses. Biological evaluation revealed that ergosterol peroxide inhibited the relaxation of supercoiled DNA (pBR322) induced by DNA topoisomerase I, and also showed marginal, selective cytotoxic activity against human colon tumor cells [COLO-205 (ED50) = 8.56 mug/mL].
