New Isocoumarin Analogues from the Marine-Derived Fungus Paraphoma sp. CUGBMF180003

Abstract

Nine new secondary metabolites, including six isocoumarin analogues, 7-hydroxyoospolactone (<b>1</b>), 7-methoxyoospolactone (<b>2</b>), 7-methoxy-9-hydroxyoospolactone (<b>3</b>), 10-acetoxy-9-hydroxyoospolactone (<b>4</b>), 6-dehydroxysescandelin (<b>5</b>), parapholactone (<b>6</b>), and three compounds with a rare skeleton of isocoumarin coupled with phenylethylamine, namely paraphamide A (<b>12</b>), paraphamide B (<b>13</b>), and paraphamide C (<b>14</b>), together with five known compounds, oospolactone (<b>7</b>), 8-<i>O</i>-methyloospolactone (<b>8</b>), 10-hydroxyoospolactone (<b>9</b>), 9,10-dihydroxyoospolactone (<b>10</b>), and oospoglycol (<b>11</b>), were isolated and identified from the marine-derived fungus <i>Paraphoma</i> sp. CUGBMF180003. Their chemical structures were determined using spectroscopic data, including HRESIMS and 1D and 2D NMR techniques. Furthermore, the stereogenic carbons in <b>5</b> and <b>14</b> were determined by comparing the experimental and calculated electronic circular dichroism (ECD) spectra. The carbon skeleton of <b>12</b>-<b>14</b> was identified as the first example of isocoumarin coupled with phenylethylamine derivatives. All of these compounds were examined for antimicrobial activities against <i>Candida albicans</i> and <i>Staphylococcus aureus.</i> Both <b>1</b> and <b>6</b> showed antibacterial activity against <i>S. aureus</i> with MIC values of 12.5 μg/mL.