Dehydrozingerone Inspired Discovery of Potential Broad-Spectrum Fungicidal Agents as Ergosterol Biosynthesis Inhibitors

Abstract

A series of dehydrozingerone derivatives were synthesized, and their fungicidal activities and action mechanism against <i>Colletotrichum musae</i> were evaluated. The bioassay result showed that most compounds exhibited excellent fungicidal activity <i>in vitro</i> at 50 μg mL^-1. Compounds <b>13</b>, <b>16</b>, <b>18</b>, <b>19</b>, and <b>27</b> exhibited broad-spectrum fungicidal activity; especially, compounds <b>19</b> and <b>27</b> were found to have more potent fungicidal activity than azoxystrobin. The EC₅₀ values of compounds <b>19</b> and <b>27</b> against <i>Rhizoctonia solani</i> were 0.943 and 0.161 μg mL^-1 respectively. Moreover, compound <b>27</b> exhibited significant <i>in vitro</i> bactericidal activity against <i>Xanthomonas oryzae</i> pv<i>. oryzae</i>, with an EC₅₀ value of 11.386 μg mL^-1, and its curative effect (49.64%) and protection effect (51.74%) on rice bacterial blight disease was equivalent to that of zhongshengmycin (42.90%, 40.80% respectively). Compound <b>27</b> could also effectively control gray mold (87.10%, 200 μg mL^-1) and rice sheath blight (100%, 200 μg mL^-1; 82.89%, 100 μg mL^-1) <i>in vivo</i>. Preliminary action mechanism study showed that compound <b>27</b> mainly acted on the cell membrane and significantly inhibited ergosterol biosynthesis in <i>Colletotrichum musae</i>.