Phytotoxic Compounds from Seriphidium transiliense: Isolation, Bioactivity Evaluation, and Preliminary Mechanistic Analysis

Extensive use of chemical herbicides has raised serious concerns regarding agricultural sustainability and ecological safety, highlighting the need for environment friendly bioherbicides. In this study, activity-guided fractionation led to the identification of xanthoxylin and α-santonin from the ethanol extract of a dominant desert plant, Seriphidium transiliense, with the phytotoxicity of xanthoxylin being reported for the first time. Petri dish bioassay revealed that both compounds significantly suppressed seedling growth of tested plants in a dose-dependent manner; at 1000 μg/mL, α-santonin inhibited root growth of Amaranthus retroflexus, Setaria viridis, Medicago sativa, and Oxybasis glauca by 98.25%, 79.75%, 71.40%, and 62.75%, respectively, whereas the corresponding inhibition rates for xanthoxylin were 59.15%, 89.71%, 38.80%, and 62.90%. Following pot experiments revealed that both compounds significantly increased MDA content and altered the activities of SOD, CAT, and POD of A. retroflexus seedlings, indicating the induction of oxidative stress. Treated plants also displayed chlorosis and leaf whitening, suggesting possible disturbance of photosynthetic pigment-related processes; subsequent molecular docking further implied that both compounds may interact with protoporphyrinogen IX oxidase (PPO), a key enzyme associated with tetrapyrrole metabolism and chlorophyll biosynthesis. Our results suggests that α-santonin and xanthoxylin have the potential to be developed as bio-herbicides.