Potent Toxic Macrocyclic Trichothecenes from the Marine-Derived Fungus Myrothecium verrucaria Hmp-F73

Activity-guided fractionation of a methanol extract from the culture broth of Myrothecium verrucaria Hmp-F73, a fungus associated with the sponge Hymeniacidon perleve, afforded six macrocyclic trichothecenes, verrucarin J (1), 8-hydroxyverrucarin J (2), verrucarin A (3), 8-acetoxyroridin (4), isororidin E (5), and roridin E (6), along with trichoverrin B (7). All seven metabolites displayed potent toxicity to the brine shrimp (Artemia sauna). In addition, compounds 2, 3, and 6 showed weak phytotoxic activities against lettuce seeds. A preliminary structure-activity relationship of the metabolites is also discussed.