Screening of Active Component form Essential Oil and Investigation of Its Synergistic Enhancement on the Mosquito-Repellent Efficacy of <i>p</i> -Menthane-3,8-diol

This study systematically evaluated the synergistic effects of terpinen-4-ol (T4O) with <i>p</i>-menthane-3,8-diol (PMD) for enhanced mosquito repellency. Through screening 20 essential oils, we identified six candidates (cinnamon, eucalyptus, tea tree, litsea cubeba, moxa, peppermint) demonstrating >85% repellency. GC-MS analysis revealed 17 candidate compounds, with T4O exhibiting strong electrophysiological responses (0.031 ± 0.002 mV). Molecular docking confirmed its high binding affinity to mosquito odorant-binding proteins, suggesting its potential as an olfactory disruptor. In PMD-based binary formulations: TP2 (20% T4O) achieved 86.9 ± 1.8% spatial repellency, 30.6% higher than PMD alone; TP1 (10% T4O) provided 6.58 ± 0.38 h of skin protection, extending PMD's efficacy by 21.6%; TP5 (50% T4O) enhanced fumigation efficacy, reducing KT₅₀ to 3.00 ± 0.32 min (78.7% decrease); TP3 (30% T4O) reduced LC₅₀ by 17.2-25.0% against larval instars I-IV. This work demonstrates T4O's multidimensional enhancement of PMD's efficacy, offering an effective natural alternative to synthetic repellents.