Viridicatumtoxin is a tetracycline-like metabolite produced by several species of Penicillium, first isolated in 1976 as a mycotoxin. Initial testing revealed that viridicatumtoxin caused myocardial deterioration, renal tubule necrosis and spleen atrophy. Analogous to the related tetracyclines, viridicatumtoxin was found to be a potent antibacterial, with activity against S. aureus including MRSA and QRSA strains. Little has been published on the mode of action of viridicatumtoxin.