Rapid Discovery of Quassinoids with Antifeedant Activity from <i>Picrasma chinensis</i> Employing Molecular Networking Integrated with Mzmine and DeepMass

The diamondback moth (<i>Plutella xylostella</i>) is a global pest of cruciferous vegetable crops. With the increase in chemical resistance, the demand for natural and highly effective plant pesticides is gradually increasing. Due to their distinctive structural features, quassinoids commonly exhibit diverse bioactivities, including insecticidal, antitumor, and anti-inflammatory properties. In this study, six undescribed (<b>1</b>-<b>6</b>) and 13 known quassinoids (<b>7</b>-<b>19</b>) were obtained from the branches and leaves of <i>Picrasma chinensis</i> based on molecular networking integrated with Mzmine and DeepMass. Their structures and configurations were established unambiguously by spectroscopic analyses, quantum chemical calculations, and by comparing experimental ECD and calculated data. Moreover, all isolates were evaluated for antifeedant activity the <i>P. xylostella</i>. Among them, compounds <b>6</b>, <b>8</b>, and <b>12</b> exhibited moderate antifeedant activity toward the diamondback moth, exhibiting selective feeding deterrence rates of 72.1 ± 0.7%, 82.8 ± 0.5%, and 83.7 ± 0.5%, respectively, at a test concentration of 200 μg/mL. This study provided a phytochemical basis for the development of innovative botanical pesticides.