Sesquiterpenoids From the Antarctic Fungus Pseudogymnoascus sp. HSX2#-11

Abstract

The fungal strains <i>Pseudogymnoascus</i> are a kind of psychrophilic pathogenic fungi that are ubiquitously distributed in Antarctica, while the studies of their secondary metabolites are infrequent. Systematic research of the metabolites of the fungus <i>Pseudogymnoascus</i> sp. HSX2#-11 led to the isolation of six new tremulane sesquiterpenoids pseudotremulanes A-F (<b>1</b>-<b>6</b>), combined with one known analog 11,12-epoxy-12β-hydroxy-1-tremulen-5-one (<b>7</b>), and five known steroids (<b>8</b>-<b>12</b>). The absolute configurations of the new compounds (<b>1</b>-<b>6</b>) were elucidated by their ECD spectra and ECD calculations. Compounds <b>1</b>-<b>7</b> were proved to be isomeride structures with the same chemical formula. Compounds <b>1</b>/<b>2</b>, <b>3</b>/<b>4</b>, <b>1</b>/<b>4</b>, and <b>2</b>/<b>3</b> were identified as four pairs of epimerides at the locations of C-3, C-3, C-9, and C-9, respectively. Compounds <b>8</b> and <b>9</b> exhibited cytotoxic activities against human breast cancer (MDA-MB-231), colorectal cancer (HCT116), and hepatoma (HepG2) cell lines. Compounds <b>9</b> and <b>10</b> also showed antibacterial activities against marine fouling bacteria <i>Aeromonas salmonicida</i>. This is the first time to find terpenoids and steroids in the fungal genus <i>Pseudogymnoascus</i>.