Cytotoxic tremulanes and 5,6-secotremulanes, four new sesquiterpenoids from a plant-associated fungus X1-2

<p>Two new tremulanes and two new 5,6-secotremulanes, davotremulanes A-D <b>1</b>–<b>4</b>, along with four known compounds <b>5</b>–<b>8</b>, were isolated from the culture extract of X1-2, an unidentified plant-associated fungus, which was isolated from the endangered plant, <i>Davidia involucrate</i> Baill. in Shennongjia District. The structures of new compounds <b>1</b>–<b>4</b> were established on the basis of extensive spectroscopic analysis. Compounds <b>1</b>–<b>8</b> were evaluated for cytotoxic activity to four cancer cell lines, and compounds <b>1</b>, <b>2</b> and <b>5</b> displayed selectively moderate activities to A549 cell line with IC<sub>50</sub> at 15.3, 25.2, 35.2 μg/mL.</p>