Amphiepicoccins A–J: Epipolythiodioxopiperazines from the Fish-Gill-Derived Fungus Epicoccum nigrumHDN17-88

Ten new epipolythiodioxopiperazines (ETPs), namely, amphiepicoccins A–J (1–10), were isolated from the fish-gill-derived fungus Epicoccum nigrumHDN17-88. Their structures were deduced from extensive spectroscopic data and electronic circular dichroism (ECD) calculations. Amphiepicoccin A (1) which contains an aromatic indole motif is unprecedented among the epicoccin type of ETPs. Compounds 1, 3, and 6displayed anti-HSV-2 activities, with IC50values of 70, 64, and 29 μM, respectively (acyclovir as positive control with an IC50value of 31 μM), while 5and 6also revealed inhibitory activity against Bacillus subtiliswith minimum inhibitory concentration (MIC) values of 13 and 25 μM, respectively.