Main Chemical Components, Activity and Mechanism of Repellence of Cyperus esculentus Essential Oil Against Tribolium...

Tribolium confusum is a major stored-product pest that exhibits resistance to chemically synthesized pest repellents. This study investigated the potential of essential oil (EO) extracted from the roots of Cyperus esculentus as a natural alternative for pest management. The EO was obtained through steam distillation, and its chemical composition was elucidated using gas chromatography-mass spectrometry. The primary compounds, cyperotundone and cyperene, were further isolated from the EO through silica gel column chromatography. The efficacy of the EO and its isolated compounds as pest repellents was evaluated against a flaxseed pest, which was identified as T. confusum through DNA sequence analysis. The results demonstrated that at 86.12 μg/cm², the EO and its two main components maintained significant repellent activity for up to 24 h. In contrast, the effectiveness of the positive control, N, N-diethyl-3-methylbenzamide (DEET) declined rapidly after 8 h. At 16 h, the repellent activity of the EO and one of its main components, cyperotundone, was significantly greater than that of DEET. Furthermore, at a lower concentration of 43.06 μg/cm², cyperotundone's repellent activity was significantly stronger than DEET's at 16 h. Additionally, cyperotundone outperformed DEET significantly from 4 to 16 h at 21.53 μg/cm² and at 16 h at 10.76 μg/cm². Among the two compounds, cyperotundone exhibited a longer-lasting repellent effect compared to cyperene, which is consistent with the lower evaporation rate of cyperotundone. Biochemical assays revealed that exposure to the EO of C. esculentus and its major compounds significantly reduced (p < 0.05) the activities of acetylcholinesterase and glutathione-S-transferase in T. confusum. Molecular docking experiments indicated that the compounds could bind to olfactory receptors with low binding energies. qRT-PCR analysis revealed that the EO and its two compounds significantly altered (p < 0.05) the expression levels of odorant receptor genes in the pest. These findings suggest that the repellent action of C. esculentus EO and its major compounds on T. confusum may be mediated through the modulation of the pest's olfactory system, as well as by inhibiting essential enzymatic activities in the pests. This research contributes valuable insights into the development of sustainable, long-lasting, and eco-friendly pest repellents, harnessing the potential of the rich botanical resource C. esculentus.