Antifungal Macrocyclic Trichothecenes from the Insect-Associated Fungus <i>Myrothecium roridum</i>

Abstract

Three new macrocyclic trichothecenes possessing rare 6'-ketal moieties, roridoxins A-C (<b>1-3</b>), and five known compounds (<b>4-8</b>) were isolated from the insect-associated fungus <i>Myrothecium roridum</i>. 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 <b>1</b> and <b>3</b> showed potent antifungal activities against four strains of phytopathogenic fungi. In addition, <b>1</b>, <b>3</b>, <b>5</b>, and <b>6</b> were found to significantly inhibit the cell growth of <i>Candida albicans</i> with minimal inhibitory concentration values from 8.8 to 18.5 μg/mL. Moreover, they were able to inhibit the biofilm formation of <i>C. albicans</i> better than the positive control.