Terretonin and its structurally related terretonins A–F have been reported; terretonin was reported as a mycotoxin5 and terretonins E and F were reported as inhibitors of the mammalian mitochondrial respiratory chain.7 Unfortunately, there has been no report about the biological activity of terretonins A–D.6 Accordingly, other biological activities of 1 in our in-house assays such as effect on cell cycle,16 lipid metabolites17 and alkaline phosphatase expression in myoblasts18 were investigated. Unfortunately, 1 showed no significant activity in these assays even at 25 μg ml−1 (data not shown). To our knowledge, this is the first report that terretonins showed antimicrobial activity.