The Polyketides and Sesquiterpenes for Enhancing Plant Resistance from Endophyte <i>Nigrospora lacticolonia</i>

Sixteen new secondary metabolites, including one unprecedented 2-butylresorcinol-ketone hybrid (<b>1</b>) with 6/6/5/6 tetra-cyclic benzannulated spiroketal scaffold, two xyloketal analogues <b>2</b> and <b>3</b> with an unique 5,6-dihydro-2<i>H</i>-pyran-2-one residue, one caryophyllene sesquiterpene (<b>4</b>), three C₁₀ polyketides (<b>6</b>, <b>7</b>, <b>9</b>), four γ-lactone derivatives (<b>12</b>, <b>14</b>-<b>16</b>), one unusual botryodiplodin-hydroxy ketone hybrid (<b>17</b>), and four unusual C₁₀ polyketide-botryodiplodin hybrids (<b>19</b>-<b>22</b>) were isolated from <i>Paris polyphylla</i> endophyte, <i>Nigrospora lacticolonia</i>. Their structures were identified mainly by NMR, ECD, and X-ray crystallography. The biosynthetic pathway of <b>1</b> was proposed. Compounds <b>6</b>-<b>8</b>, <b>12</b>, <b>17</b>, <b>19</b>, and <b>21</b> demonstrated significant antiphytopathogenic activities against <i>Fusarium oxysporum</i>, comparable to nystatin. Most compounds exhibited growth-promoting effects on rice seeds under <i>F. oxysporum</i>, salinity, and cold stresses. At 100 μg/mL, compounds <b>3</b> and <b>16</b> exhibited insecticidal activities with mortality rates of 55.0% and 48.3%, respectively. Significantly, compound <b>3</b> showed plant resistance against phytopathogens, salt stress, and insecticidal activity. The structure-activity relationship was also discussed.