Antifungal Macrocyclic Trichothecenes from the Insect-Associated Fungus Myrothecium roridum

Three new macrocyclic trichothecenes possessing rare
6′-ketal
moieties, roridoxins A–C (1–3), and five
known compounds (4–8) were isolated from the insect-associated
fungus Myrothecium roridum. Their structures
were confirmed by a combination of NMR and HRESIMS data, while their
absolute configurations were unambiguously determined by single-crystal
X-ray analysis and electronic circular dichroism experiments. Trichothecenes 1 and 3 showed potent antifungal activities against
four strains of phytopathogenic fungi. In addition, 1, 3, 5, and 6 were found to
significantly inhibit the cell growth of Candida albicans with minimal inhibitory concentration values from 8.8 to 18.5 μg/mL.
Moreover, they were able to inhibit the biofilm formation of C. albicans better than the positive control.