Sclerotiorin-Type Azaphilones Isolated from a Marine-Derived Fungus <i>Microsphaeropsis arundinis</i> P1B

Seven pairs of new epimers, microsphazaphilones A-G (<b>1</b>, <b>3, 5</b>, <b>7</b>, <b>9</b>, <b>11</b>, and <b>13</b>) and epimicrosphazaphilones A-G (<b>2</b>, <b>4, 6</b>, <b>8</b>, <b>10</b>, <b>12</b>, and <b>14</b>), were isolated and identified from the fermentation of a marine-derived fungus <i>Microsphaeropsis arundinis</i> P1B. Their structures, including the absolute configurations, were determined by NMR and MS data analysis, comparison of experimental and calculated electronic circular dichroism (ECD) curves, and dimolybdenum tetraacetate induced ECD. Microsphazaphilones A-G and epimicrosphazaphilones A-G represent the sclerotiorin-type azaphilones with a rare γ-lactone or a tetrahydrofuran fragment at the end of the branched C₇ side chain at the C-3 position of the pyranoquinone core skeleton. Among them, compound <b>2</b> demonstrated the strongest anti-inflammatory activity that inhibited the expression of multiple inflammatory factors in LPS-induced Raw264.7 cells, possibly through the inhibition of the Erk1/2 MAPK signaling pathway.