Acaricidal efficacy and biochemical effects of Cananga odorata essential oil and three selected compounds against Haemaphysalis doenitzi (Acari: Ixodidae)

Abstract Background Ticks are major ectoparasites that significantly impact livestock productivity worldwide. With the growing resistance to synthetic acaricides and increasing concerns about environmental and human safety, identifying effective and ecofriendly alternatives has become a pressing need. This study evaluated the fumigant and contact toxicities of ylang-ylang ( Cananga odorata ) essential oil (EO) and three plant-derived compounds, lilial, cinene, and α-amylcinnamaldehyde, against Haemaphysalis doenitzi and explored their underlying mechanisms of action. Methods The acaricidal potential of C. odorata EO, lilial, cinene, and α-amylcinnamaldehyde against H. doenitzi was evaluated through in vitro (fumigation and immersion tests) and subsequent biochemical effects experiments. Surviving adult ticks treated with the semi-lethal concentration (LC 50 ) were homogenized to detect GST, Na⁺/K⁺-ATPase, AchE, and CarE activities, and HDABCE1, HD-GSTa, and HDCYP450a transcripts were quantified via reverse-transcription quantitative polymerase chain reaction (RT–qPCR). Homology models of the three proteins were built and docked with lilial, cinene, and α-amylcinnamaldehyde to predict binding sites and affinities. Results In the fumigation assay, C. odorata EO and lilial showed the highest activity with the lowest LC 50 value (27.904 and 27.173 µg/mL, respectively), outperforming cinene and α-amylcinnamaldehyde. In the immersion test, all substances exhibited significant acaricidal activity, with α-amylcinnamaldehyde achieving 100% mortality in both nymphs and adults at 50 mg/mL after 24 h. α-Amylcinnamaldehyde LC 50 was 4.4 mg/mL for nymphs and 10.8 mg/mL for adults. Enzyme assays indicated that lilial and C. odorata EO significantly inhibited GST and AchE, while cinene and α-amylcinnamaldehyde primarily induced CarE activity. Gene expression analysis further revealed that cinene and C. odorata EO significantly upregulated HD-GSTa and HD-CYP450ais>; lilial and C. odorata EO strongly elevated HDABCE1, and α-amylcinnamaldehyde markedly induced HD-CYP450ais>. Molecular docking supported these findings, showing that each compound interacts with HD-GSTa, HD-CYP450a, and HD-ABCE1 proteins through distinct binding modes, consistent with their differential mechanisms of action. Conclusions Cananga odorata EO, cinene, lilial, and α-amylcinnamaldehyde potently exhibit acaricidal activity via distinct but complementary disruption of detox enzymes, neurotransmission, and efflux pumps, offering a basis for novel plant-derived acaricides.